Method of enantioselectively catalyzing a reaction

Abstract

A chiral catalyst is disclosed together with methods of using it for enantioselective syntheses. The chiral catalyst includes a nucleus with two metal atoms that has four bridging ligands oriented radially to the axis of the nucleus. Each of these ligands includes a two complexing atoms each complexed to one of the metal atoms. At least one of the bridging ligands includes a chiral center which is bonded to one of the complexing atoms. Preferably, all four of the bridging ligands include a chiral center bonded to one of the complexing atoms. The catalyst of the invention has been found to be useful in catalyzing carbenoid transformation reactions such as cyclopropanation.

1. A method of enantioselectively inserting a carbene between a carbon and a hydrogen comprising the steps of:
 providing a compound with a carbon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand further comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said second bridging ligand further comprising a ring including said second complexing atom and attached to said first complexing atom, said ring also including a chiral center attached through a first bonding site to said second complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and wherein the R/S configuration of the chiral center on the second bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       2. A method of enantioselectively inserting a carbene between a carbon and a hydrogen comprising the steps of:
 providing a compound with a carbon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said first bridging ligand further comprising a second chiral center attached through a first bonding site to said second complexing atom, having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       3. A method of enantioselectively inserting a carbene between a carbon and a hydrogen comprising the steps of:
 providing a compound with a carbon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent; and  
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured, and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       4. A method of enantioselectively inserting a carbene between a carbon and a hydrogen comprising the steps of:
 providing a compound with a carbon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 said second bridging ligand further comprising a chiral center attached through a first bonding site to the second complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 
 wherein the R/S configuration of the chiral centers on the first and second bridging ligands are all the same; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       5. A method of enantioselectively inserting a carbene between a carbon and a hydrogen comprising the steps of:
 providing a compound with a carbon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound of said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       6. The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the compound is selected from the group consisting of 3-(N-diazoacetyl)aminopropionate, 2,5-dimethyl-4-hexen-2-yl diazoacetate, N-(diazoacetylamino)acetate, n-octyl diazoacetate, and N-(1-butyl)diazoacetamide. 
     
     
       7. The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the carbene precursor is a diazo carbonyl compound. 
     
     
       8. The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the carbene precursor is a diazo compound selected from the group consisting of ethyl diazoacetate, t-butyl diazoacetate, and menthyl diazoacetate. 
     
     
       9. The method of  claim 1 ,  2 ,  3 ,  4  or  5  wherein the carbene precursor is on the compound with the carbon-hydrogen bond. 
     
     
       10. A method of enantioselectively inserting a carbene between an oxygen and a hydrogen comprising the steps of:
 providing a compound with an oxygen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand further comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said second bridging ligand further comprising a ring including said second complexing atom and attached to said first complexing atom, said ring also including a chiral center attached through a first bonding site to said second complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and wherein the R/S configuration of the chiral center on the second bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene, insertion to proceed.  
 
     
     
       11. A method of enantioselectively inserting a carbene between an oxygen and a hydrogen comprising the steps of:
 providing a compound with an oxygen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said first bridging ligand further comprising a second chiral center attached through a first bonding site to said second complexing atom, having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       12. A method of enantioselectively inserting a carbene between an oxygen and a hydrogen comprising the steps of:
 providing a compound with an oxygen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent; and  
 
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured, and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       13. A method of enantioselectively inserting a carbene between an oxygen and a hydrogen comprising the steps of:
 a providing a compound with an oxygen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 said second bridging ligand further comprising a chiral center attached through a first bonding site to the second complexing atom, and having a second bonding site occupied by a first substituent, and having a fourth bonding site occupied by second substituent, and having a fourth bonding site occupied by a third substituent, and  
 
 wherein the R/S configuration of the chiral centers on the first and second bridging ligands are all the same; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       14. A method of enantioselectively inserting a carbene between an oxygen and a hydrogen comprising the steps of:
 providing a compound with an oxygen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       15. The method of  claim 10 ,  11 ,  12 ,  13  or  14  wherein the compound is selected from the group consisting of cis-1,2-cyclohexanediol, 1-phenylethanol, methanol, and 2-butanol. 
     
     
       16. The method of  claim 12 ,  11 ,  12 ,  13  or  14  wherein the carbene precursor is a diazo carbonyl compound. 
     
     
       17. The method of  claim 10 ,  11 ,  12 ,  13  or  14  wherein the carbene precursor is a diazo compound selected from the group consisting of ethyl diazo acetate, t-butyl diazoacetate, menthyl diazoacetate, and 3-diazo-2-butanone. 
     
     
       18. The method of  claim 10 ,  11 ,  12 ,  13  or  14  wherein the carbene precursor is on the compound with the oxygen-hydrogen bond. 
     
     
       19. A method of enantioselectively inserting a carbene between a nitrogen and a hydrogen comprising the steps of:
 providing a compound with a nitrogen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand further comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said second bridging ligand further comprising a ring including said second complexing atom and attached to said first complexing atom, said ring also including a chiral center attached through a first bonding site to said second complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and wherein the R/S configuration of the chiral center on the second bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       20. A method of enantioselectively inserting a carbene between a nitrogen and a hydrogen comprising the steps of:
 providing a compound with a nitrogen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said first bridging ligand further comprising a second chiral center attached through a first bonding site to said second complexing atom, having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       21. A method of enantioselectively inserting a carbene between a nitrogen and a hydrogen comprising the steps of:
 providing a compound with a nitrogen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent; and  
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured, and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       22. A method of enantioselectively inserting a carbene between a nitrogen and a hydrogen comprising the steps of:
 providing a compound with a nitrogen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a third bonding site occupied by a first substituent having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 said second bridging ligand further comprising a chiral center attached through a first bonding site to the second complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 
 wherein the R/S configuration of the chiral centers on the first and second bridging ligands are all the same; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       23. A method of enantioselectively inserting a carbene between a nitrogen and a hydrogen comprising the steps of:
 providing a compound with a nitrogen-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       24. The method of  claim 19 ,  20 ,  21 ,  22  or  23  wherein the compound is selected from the group consisting of N-(1-phenylethyl)acetamide, N-(2-butyl)acetamide, and 3-acetyl-B*-lactam. 
     
     
       25. The method of  claim 19 ,  20 ,  21 ,  22 , or  23  wherein the carbene precursor is a diazo carbonyl compound. 
     
     
       26. The method of  claim 19 ,  20 ,  21 ,  22  or  23  wherein the carbene precursor is a diazo compound selected from the group consisting of ethyl diazo acetate, t-butyl diazoacetate, methyl diazoacetate, and 3-diazo-2-butanone. 
     
     
       27. The method of  claim 19 ,  20 ,  21 ,  22  or  23  wherein the carbene precursor is on the compound with the nitrogen-hydrogen bond. 
     
     
       28. A method of enantioselectively inserting a carbene between a silicon and a hydrogen comprising the steps of:
 providing a compound with a silicon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand further comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said second bridging ligand further comprising a ring including said second complexing atom and attached to said first complexing atom, said ring also including a chiral center attached through a first bonding site to said second complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and wherein the R/S configuration of the chiral center on the second bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       29. A method of enantioselectively inserting a carbene between a silicon and a hydrogen comprising the steps of:
 providing a compound with a silicon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said first bridging ligand further comprising a second chiral center attached through a first bonding site to said second complexing atom, having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to said carbene insertion to proceed.  
 
     
     
       30. A method of enantioselectively inserting a carbene between a silicon and a hydrogen comprising the steps of:
 providing a compound with a silicon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexing to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent; and  
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured, and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       31. A method of enantioselectively inserting a carbene between a silicon and a hydrogen comprising the steps of:
 providing a compound with a silicon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 said second bridging ligand further comprising a chiral center attached through a first bonding site to the second complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 
 wherein the R/S configuration of the chiral centers on the first and second bridging ligands are all the same; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       32. A method of enantioselectively inserting a carbene between a silicon and a hydrogen comprising the steps of:
 providing a compound with a silicon-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       33. The method of  claim 28 ,  29 ,  30 ,  31  or  32  wherein the carbene precursor is a diazo carbonyl compound. 
     
     
       34. The method of  claim 28 ,  29 ,  30 ,  31  or  32  wherein the carbene precursor is a diazo compound selected from the group consisting of ethyl diazo acetate, t-butyl diazoacetate, methyl diazoacetate, and 3-diazo-2-butanone. 
     
     
       35. The method of  claim 28 ,  29 ,  30 ,  31  or  32  wherein the carbene precursor is on the compound with the silicon-hydrogen bond. 
     
     
       36. A method of enantioselectively inserting a carbene between a sulfur and a hydrogen comprising the steps of:
 providing a compound with a sulfur-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand further comprising a ring including said first complexing atom and attached to said second complexing atom, said rig also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said second bridging ligand further comprising a ring including said second complexing atom and attached to said first complexing atom, said ring also including a chiral center attached through a first bonding site to said second complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and wherein the R/S configuration of the chiral center on the second bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       37. A method of enantioselectively inserting a carbene between a sulfur and a hydrogen comprising the steps of:
 providing a compound with a sulfur-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and  
 said first bridging ligand further comprising a second chiral center attached through a first bonding site to said second complexing atom, having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       38. A method of enantioselectively inserting a carbene between a sulfur and a hydrogen comprising the steps of:
 providing a compound with a sulfur-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,  
 said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent; and  
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured, and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       39. A method of enantioselectively inserting a carbene between a sulfur and a hydrogen comprising the steps of:
 providing a compound with a sulfur-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, sand having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 said second bridging ligand further comprising a chiral center attached through a first bonding site to the second complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 
 wherein the R/S configuration of the chiral centers on the first and second bridging ligands are all the same; and  
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       40. A method of enantioselectively inserting a carbene between a sulfur and a hydrogen comprising the steps of:
 providing a compound with a sulfur-hydrogen bond;  
 providing a carbene precursor, wherein either said compound or said carbene precursor is prochiral;  
 providing a chiral catalyst comprising 
 a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and  
 first, second, third and fourth bridging ligands oriented radially to the axis, 
 each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,  
 said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and  
 blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured and oriented so as to substantially impair approach to the second metal atom along said axis; and  
 
 
 reacting said compound, said carbene precursor, and said chiral catalyst under conditions sufficient to cause said carbene insertion to proceed.  
 
     
     
       41. The method of  claim 36 ,  37 ,  38 ,  39  or  40  wherein the carbene precursor is a diazo carbonyl compound. 
     
     
       42. The method of  claim 36 ,  37 ,  38 ,  39  or  40  wherein the carbene precursor is a diazo compound, selected from the group consisting of ethyl diazo acetate, t-butyl diazoacetate, methyl diazoacetate, and 3-diazo-2-butanone. 
     
     
       43. The method of  claim 36 ,  37 ,  38 ,  39  or  40  wherein the carbene precursor is on the compound with the sulfur-hydrogen bond. 
     
     
       44. The method of claims  1 ,  10 ,  19 ,  28  or  36  wherein one and only one of the first and second substituents on the chiral center of the first bridging ligand is a first carboxylate group attached to the chiral center by the carbonyl carbon, and wherein one and only one of the first and second substituents on the chiral center of the second bridging ligand is a second carboxylate group attached to the chiral center by the carbonyl carbon. 
     
     
       45. The method of  claim 44  wherein the first and second carboxylate groups are independently selected from the group consisting of methyl carboxylate and isopropyl carboxylate. 
     
     
       46. The method of claims  2 ,  11 ,  20 ,  29  or  37  wherein one and only one of the first and second substituents on the first chiral center of the first bridging ligand is a first carboxylate group attached to the first chiral center by the carbonyl carbon, and wherein one and only one of the first and second substituents on the second chiral center of the first bridging ligand is a second carboxylate group attached to the second chiral center by the carbonyl carbon. 
     
     
       47. The method of  claim 46  wherein the first and second carboxylate groups are independently selected from the group consisting of methyl carboxylate and isopropyl carboxylate. 
     
     
       48. The method of claims  3 ,  12 ,  21 ,  30  or  38  wherein one and only one of the first and second substituents on the chiral center of the first bridging ligand is a carboxylate group attached to the chiral center by the carbonyl carbon. 
     
     
       49. The method of  claim 48  wherein the carboxylate group is selected from the group consisting of methyl carboxylate and isopropyl carboxylate. 
     
     
       50. The method of  claim 4 ,  13 ,  22 ,  31  or  39  wherein one or two, but not three, of the first, second and third substituents on the chiral center of the first bridging ligand is a first carboxylate group attached to the chiral center by the carbonyl carbon, and wherein one or two, but not three, of the first, second and third substituents on the chiral center of the second bridging ligand is a second carboxylate group attached to the chiral center by the carbonyl carbon. 
     
     
       51. The method of  claim 50  wherein the first and second carboxylate groups are independently selected from the group consisting of methyl carboxylate and isopropyl carboxylate. 
     
     
       52. The method of claims  5 ,  14 ,  23   32 , or  40  wherein one or tow, but not three, of the first, second and third substituents on the chiral center of the first bridging ligand is a carboxylate group attached to the chiral center by the carbonyl carbon. 
     
     
       53. The method of  claim 52  wherein the carboxylate group is selected from the group consisting of methyl carboxylate and isopropyl carboxylate. 
     
     
       54. A method of enantioselectively catalyzing a reaction comprising the steps of:
   providing a prochiral compound,        providing a chiral catalyst comprising      a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and        first, second, third and fourth bridging ligands oriented radially to the axis,      each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,        said first bridging ligand further comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and        said second bridging ligand further comprising a ring including said second complexing atom and attached to said first complexing atom, said ring also including a chiral center attached through a first bonding site to said second complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and wherein the R/S configuration of the chiral center on the second bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand; and            reacting said prochiral compound and said chiral catalyst under conditions sufficient cause the reaction.     
     
     
       55. The method of  claim 54  wherein said third bridging ligand further comprises a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by hydrogen, and wherein the R/S configuration of the chiral center on the third bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand. 
     
     
       56. The method of  claim 55  wherein said fourth bridging ligand further comprising a ring including said second complexing atom and attached to said first complexing atom, said ring also including a chiral center attached through a first bonding site to said second complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by hydrogen, and wherein the R/S configuration of the chiral center on the fourth bridging ligand is the same as the R/S configuration of the chiral center on the first bridging ligand. 
     
     
       57. The method of  claim 54  wherein the bridging ligands with a chiral center are selected from the group consisting of: Oxazolidinones, Pyrrolidinones, *B- lactams, *Y - lactams, *S - lactams, and their analogs wherein S replaces O as the complexing atom.   
     
     
       58. The method of  claim 54  wherein the bridging ligands with a chiral center are selected from the group consisting of: (   4 S )  isopropyl oxazolidinone,  (   4 S )  benzyl oxazolidinone,  (   4 S )  methyl oxazolidinone,  (   5 S )  methyl  2   - pyrrolidinone -   5   - carboxylate,  (   5 S )  isopropyl  2   - pyrrolidinone -   5   - carboxylate.   
     
     
       59. A method of enantioselectively catalyzing a reaction comprising the steps of:
   providing a prochiral compound,        providing a chiral catalyst comprising      a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and        first, second, third and fourth bridging ligands oriented radially to the axis,      each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,        said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and        said second bridging ligand further comprising a chiral center attached through a first bonding site to the second complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and          wherein the R/S configuration of the chiral centers on the first and second bridging ligands are all the same; and          reacting said prochiral compound and said chiral catalyst under conditions sufficient cause the reaction.     
     
     
       60. The method of  claim 54  or  59  wherein the first and second bridging ligand are radially adjacent. 
     
     
       61. The method of  claim 54  or  59  wherein the first and second bridging ligand are radially opposite. 
     
     
       62. The method of  claim 54  or  59  wherein one and only one of the first and second substituents on the chiral center of the first bridging ligand is a first carboxylate group attached to the chiral center by the carbonyl carbon, and wherein one and only one of the first and second substituents on the chiral center of the second bridging ligand is a second carboxylate group attached to the chiral center by the carbonyl carbon. 
     
     
       63. The method of  claim 62  wherein the first and second carboxylate groups are independently selected from the group consisting of methyl carboxylate and isopropyl carboxylate. 
     
     
       64. A method of enantioselectively catalyzing a reaction comprising the steps of:
   providing a prochiral compound,        providing a chiral catalyst comprising      a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and        first, second, third and fourth bridging ligands oriented radially to the axis,      each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,        said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent, and        said first bridging ligand further comprising a second chiral center attached through a first bonding site to said second complexing atom, having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent; and            reacting said prochiral compound and said chiral catalyst under conditions sufficient cause the reaction.     
     
     
       65. A method of enantioselectively catalyzing a reaction comprising the steps of:
   providing a prochiral compound,        providing a chiral catalyst comprising      a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and        first, second, third and fourth bridging ligands oriented radially to the axis,      each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed to said second metal atom,        said first bridging ligand also comprising a ring including said first complexing atom and attached to said second complexing atom, said ring also including a chiral center attached through a first bonding site to said first complexing atom, attached through a second bonding site to said ring, having a third bonding site occupied by a first substituent, and having a fourth bonding site occupied by a second substituent; and        blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured, and oriented so as to substantially impair approach to the second metal atom along said axis; and            reacting said prochiral compound and said chiral catalyst under conditions sufficient cause the reaction.     
     
     
       66. A method of enantioselectively catalyzing a reaction comprising the steps of:
   providing a prochiral compound,        providing a chiral catalyst comprising      a nucleus with a first and second atom of the same metal aligned on an axis, said metal selected from the group consisting of rhodium, ruthenium, chromium, molybdenum, tungsten, rhenium and osmium; and        first, second, third and fourth bridging ligands oriented radially to the axis,      each ligand having a first and second complexing atom, the first complexing atom of each of said bridging ligands being complexed with said first metal atom, and the second complexing atom of each of said bridging ligands being complexed with said second metal atom,        said first bridging ligand further comprising a chiral center attached through a first bonding site to the first complexing atom, and having a second bonding site occupied by a first substituent, having a third bonding site occupied by a second substituent, and having a fourth bonding site occupied by a third substituent, and        blocking structure bonded to at least one of said first, second, third, and fourth bridging ligands, said blocking structure being constituted, configured and oriented so as to substantially impair approach to the second metal atom along said axis; and            reacting said prochiral compound and said chiral catalyst under conditions sufficient cause the reaction.     
     
     
       67. The method of  claim 54 ,  59 ,  64 ,  65 , or  66  wherein one of the substituents on the first bridging ligand is hydrogen. 
     
     
       68. The method of  claim 54 ,  59 ,  64 ,  65  or  66  wherein said first, second, third, and fourth bridging ligands are all the same. 
     
     
       69. The method of  claim 54 ,  59 ,  64 ,  65  or  66  wherein the complexing atom to which the chiral centers are bonded is nitrogen. 
     
     
       70. The method of  claim 54 ,  59 ,  64 ,  65  or  66  wherein the ratio of the volume of the first substituents to the volume of the second substituents on each of the chiral centers is less than about  0 . 8 . 
     
     
       71. The method of  claim 54 ,  59 ,  64 ,  65  or  66  wherein the ratio of the volume of the first substituents to the volume of the second substituents on each of the chiral centers is less than about  0 . 5