Catalysts

Abstract

Polymerisation catalysts and systems comprising said catalysts for polymerising carbon dioxide and an epoxide, a lactide and/or lactone, and/or an epoxide and an anhydride. The catalyst is of formula (I): Wherein M 1 and M 2 are independently selected from Zn(II), Cr(II), Co(II), Cu(II), Mn(II), Ni(II), Mg(II), Fe(II), Ti(II), V(II), Cr(III)-X, Co(III)-X, Ni(III)-X, Mn(III)-X, Fe(III)-X, Ca(II), Ge(II), AI(III)-X, Ti(III)-X, V(III)-X, Ge(IV)-(X) 2 or Ti(IV)-(X) 2 . R 3A is different from R 3B ; and/or at least one occurrence of E 3 , E 4 , E 5 and E 6 is different to a remaining occurrence of E 3 , E 4 , E 5 and E 6 . A ligand, a process of asymmetric N-substitution of a symmetrical ligand and a process for the reaction of: (i) carbon dioxide with an epoxide; (ii) an epoxide and an anhydride; and/or (iii) a lactide and/or a lactone, in the presence of a catalyst is also described.

1 . A catalyst of formula (I): 
       
         
           
           
               
               
           
         
         wherein: 
         M 1  and M 2  are independently selected from Zn(II), Cr(II), Co(II), Cu(II), Mn(II), Ni(II), Mg(II), Fe(II), Ti(II), V(II), Cr(III)-X, Co(III)-X, Ni(III)-X, Mn(III)-X, Fe(III)-X, Ca(II), Ge(II), AI(III)-X, Ti(III)-X, V(III)-X, Ge(IV)-(X) 2  or Ti(IV)-(X) 2 ; 
         R 1  and R 2  are independently selected from hydrogen, halide, a nitro group, a nitrile group, an imine, an amine, an ether group, a silyl group, a silyl ether group, a sulfoxide group, a sulfonyl group, a sulfinate group or an acetylide group or an optionally substituted alkyl, alkenyl, alkynyl, haloalkyl, aryl, heteroaryl, alkoxy, aryloxy, alkylthio, arylthio, alicyclic or heteroalicyclic group; 
         R 3A  and R 3B  are independently selected from optionally substituted alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene, arylene, heteroarylene or cycloalkylene, wherein alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene and heteroalkynylene, may optionally be interrupted by aryl, heteroaryl, alicyclic or heteroalicyclic; 
         R 5  is independently selected from H, or optionally substituted aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl, heteroaryl, alkylheteroaryl or alkylaryl; 
         E 1  is C, E 2  is O, S or NH or E 1  is N and E 2  is O; 
         E 3 , E 4 , E 5  and E 6  are each independently selected from N, NR 4 , O and S, wherein when any of E 3 , E 4 , E 5  or E 6  are N,   is  , and wherein when any of E 3 , E 4 , E 5  or E 6  are NR 4 , O or S,   is  ; R 4  is independently selected from H, or optionally substituted aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl, heteroaryl, alkylheteroaryl or alkylaryl; 
         X is independently selected from OC(O)R x , OSO 2 R x , OSOR x , OSO(R x ) 2 , S(O)R x , OR x , phosphinate, halide, nitrate, hydroxyl, carbonate, amino, amido or optionally substituted aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl or heteroaryl; 
         R x  is independently hydrogen, or optionally substituted aliphatic, haloaliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl, alkylaryl or heteroaryl; and 
         G is absent or independently selected from a neutral or anionic donor ligand which is a Lewis base; 
         and wherein:
 i) R 3A  is different from R 3B ; and/or 
 ii) At least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 . 
 
       
     
     
         2 . The catalyst of  claim 1 , wherein R 3A  is different from R 3B , and each occurrence of E 3 , E 4 , E 5  and E 6  is the same. 
     
     
         3 . The catalyst of  claim 1 , wherein R 3A  is the same as R 3B  and at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and Ee. 
     
     
         4 . The catalyst of  claim 1 , wherein R 3A  is different from R 36  and at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 . 
     
     
         5 . The catalyst of  claim 1 , wherein E 3  and E 5  are the same, and E 4  and E 6  are the same, and wherein E 3  and E 5  are different from E 4  and E 6 . 
     
     
         6 . The catalyst of  claim 1 , wherein E 3  and E 4  are the same, and E 5  and E 6  are the same, and wherein E 3  and E 4  are different from E 5  and E 6 . 
     
     
         7 . The catalyst of  claim 1 , wherein R 3A  or R 3B  is selected from substituted or unsubstituted alkylene, substituted or unsubstituted cycloalkylene or optionally substituted arylene. 
     
     
         8 . The catalyst of  claim 1 , wherein R 3A  is different from R 3B , R 3A  is substituted or unsubstituted alkylene. 
     
     
         9 . The catalyst of  claim 1 , wherein R 3A  is different from R 3B  and wherein R 3A  is 2,2-dimethylpropylene and R 3B  is phenylene, or R 3A  is a disubstituted cycloalkylene which acts as a bridging group between two nitrogen centers in the catalyst of formula (I) and R 3B  is 2,2-dimethylpropylene, or R 3A  is 2,2-dimethylpropylene and R 3B  is propylene or ethylene, or R 3A  is propylene, and R 38  is 2,2-dimethylpropylene. 
     
     
         10 . The catalyst of  claim 1 , wherein each E 3 , E 4 , E 5  and E 6  is NR 4 , and one of the R 4  groups is different. 
     
     
         11 . The catalyst of  claim 1 , wherein each ES, E 4 , E 5  and E 6  is NR 4 , and two of the R 4  groups are different. 
     
     
         12 . The catalyst of  claim 1 , wherein two of E 3 , E 4 , E 5  and E 6  are NR 4 , and two of E 3 , E 4 , E 5  and E 6  are N. 
     
     
         13 . The catalyst of  claim 1 , wherein two of E 3 , E 4 , E 5  and E 6  are S, and two of E 3 , E 4 , E 5  and E 6  are NR 4 . 
     
     
         14 . The catalyst of  claim 1 , wherein each occurrence of R 2  and R 5  are H, E 1  is C and E 2  is O, S or NH. 
     
     
         15 . The catalyst of  claim 1 , wherein M 1  or M 2  is selected from Mg(II), Ni(II), Ni(III)-X, Co(II), Co(III)-X and Zn(II). 
     
     
         16 . The catalyst of  claim 1 , wherein M 1  or M 2  is selected from Ni(II) or Mg(II). 
     
     
         17 . The catalyst of  claim 1 , wherein M 1  and M 2  are the same. 
     
     
         18 . The catalyst of  claim 1 , wherein M 1  and M 2  are the same and are Ni(II) or Mg(III). 
     
     
         19 . The catalyst of  claim 1 , wherein M 1  and M 2  are the same and are Ni(II), and each E 3 , E 4 , E 5  and E 6  is NR 4 , wherein at least one of the R 4  groups is different from a remaining occurrence of R 4  and is selected from an optionally substituted alkyl or heteroalkyl. 
     
     
         20 . The catalyst according to  claim 1 , wherein R 1  is independently selected from hydrogen, halide, amino, nitro, sulfoxide, sulfonyl, sulfinate, and optionally substituted alkyl, alkenyl, aryl, heteroaryl, alkoxy or alkylthio. 
     
     
         21 . The catalyst of  claim 1 , wherein each occurrence of R 1  is the same. 
     
     
         22 . The catalyst according to  claim 1 , wherein X is independently OC(O)R x , OSO 2 R x , OS(O)R x , OSO(R x ) 2 , S(O)R x , OR x , halide, nitrate, hydroxyl, carbonate, amino, nitro, amido, and optionally substituted alkyl, heteroalkyl, aryl or heteroaryl. 
     
     
         23 . The catalyst according to  claim 1 , wherein R x  is independently optionally substituted alkyl, alkenyl, alkynyl, heteroalkyl, aryl, heteroaryl or alkylaryl. 
     
     
         24 . The catalyst of  claim 1 , wherein both occurrences of R 1  are the same, and are selected from hydrogen, halide, amino, nitro, sulfoxide, sulfonyl, sulfinate, silyl, silyl ether and an optionally substituted alkyl, alkenyl, aryl, heteroaryl, alkoxy, aryloxy or alkylthio;
 R 2  is hydrogen;   R 3A  and R 3B  are the same or different, and are selected from substituted or unsubstituted alkylene, substituted or unsubstituted cycloalkylene and substituted or unsubstituted arylene;   E 3  to E 6  are the same or different and are selected from NR 4 , S, N or O;   R 4  is hydrogen, an optionally substituted alkyl or heteroalkyl;   each X is the same, and is selected from OC(O)R x , OR x , halide, carbonate, amino, nitro, alkyl, aryl, heteroaryl, phosphinate or OSO 2 R x ,   R x  is alkyl, alkenyl, alkynyl, heteroalkyl, aryl, heteroaryl or alkylaryl;   each G, where present, is independently selected from halide; water; a heteroaryl optionally substituted by alkyl, alkenyl, alkynyl, alkoxy, halogen, hydroxyl, nitro or nitrile;   M 1  and M 2  are independently selected from Mg(II), Zn(II), Ni(II), Ni(III)-X, Cr(II), Cr(III)-X, Co(II), Co(III)-X Mn(II), Fe(II), and Fe(II)-X.   
     
     
         25 . The catalyst of  claim 1 , wherein both occurrences of R 1  are the same, and are selected from hydrogen, halide, amino, nitro, sulfoxide, sulfonyl, sulfinate, silyl, silyl ether and an optionally substituted alkyl, alkenyl, aryl, heteroaryl, alkoxy, aryloxy or alkylthio;
 R 2  is hydrogen;   R 3A  is a substituted or unsubstituted cycloalkylene or alkylene and R 3B  is a substituted or unsubstituted alkylene, or arylene;   each occurrence of E 3  to E 6  is NR 4 ;   R 4  is hydrogen;   each X is the same, and is selected from OC(O)R x , OR x , halide, carbonate, amino, nitro, alkyl, aryl, heteroaryl, phosphinate or OSO 2 R x ,   R x  is alkyl, alkenyl, alkynyl, heteroalkyl, aryl, heteroaryl or alkylaryl;   each G, where present, is independently selected from halide; water; a heteroaryl optionally substituted by alkyl, alkenyl, alkynyl, alkoxy, halogen, hydroxyl, nitro or nitrile;   M 1  and M 2  are independently selected from Mg(II), Zn(II), Ni(II), Ni(II)-X, Cr(II), Cr(III)-X, Co(II), Co(III)-X, Mn(II), Fe(II), and Fe(III)-X.   
     
     
         26 . The catalyst of  claim 1 , wherein both occurrences of R 1  are the same, and are selected from hydrogen, halide, amino, nitro, sulfoxide, sulfonyl, sulfinate, silyl, silyl ether and an optionally substituted alkyl, alkenyl, aryl, heteroaryl, alkoxy, aryloxy or alkylthio;
 R 2  is hydrogen;   R 3A  and R 3B  are the same and are substituted or unsubstituted alkylene;   each of E 3 , E 4 , E 5  and E 6  is NR 4  wherein one of the R 4  groups is different and selected from an optionally substituted alkyl or heteroalkyl and the remaining R 4  groups are hydrogen;   each X is the same, and is selected from OC(O)R x , OR x , halide, carbonate, amino, nitro, alkyl, aryl, heteroaryl, phosphinate or OSO 2 R,   R x  is alkyl, alkenyl, alkynyl, heteroalkyl, aryl, heteroaryl or alkylaryl;   each G, where present, is independently selected from halide; water; a heteroaryl optionally substituted by alkyl, alkenyl, alkynyl, alkoxy, halogen, hydroxyl, nitro or nitrile;   M1 and M2 are independently selected from Mg(II), Zn(II), Cr(II), Cr(III)-X, Co(II), Co(III)-X, Mn(II), Ni(II), Ni(II)-X, Fe(III), and Fe(III)-X.   
     
     
         27 . The catalyst of  claim 1 , wherein both occurrences of R 1  are the same, and are selected from hydrogen, halide, amino, nitro, sulfoxide, sulfonyl, sulfinate, silyl, silyl ether and an optionally substituted alkyl, alkenyl, aryl, heteroaryl, alkoxy, aryloxy or alkylthio;
 R 2  is hydrogen;   R 3A  and R 3B  are selected from substituted or unsubstituted alkylene, substituted or unsubstituted cycloalkylene and substituted or unsubstituted arylene;   E 3  to E 6  are selected from N, NR 4 , S or O;   R 4  is selected from hydrogen, or optionally substituted alkyl or heteroalkyl;   each X is the same, and is selected from OC(O)R x , OR x , or OSO 2 R,   R x  is alkyl, alkenyl, alkynyl, heteroalkyl, aryl, heteroaryl or alkylaryl;   each G, where present, is independently selected from halide; water; a heteroaryl optionally substituted by alkyl, alkenyl, alkynyl, alkoxy, halogen, hydroxyl, nitro or nitrile;   M 1  and M 2  are independently selected from Mg(II), Zn(II), Cr(III), Cr(III)-X, Co(II), Co(III)-X, Mn(II), Ni(II), Ni(III)-X, Fe(II), and Fe(III)-X, ) and wherein:   (i) R 3A  is different from R 3B ; and/or   (ii) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 .   
     
     
         28 . The catalyst of  claim 1 , wherein both occurrences of R 1  are the same, and are selected from an optionally substituted alkyl;
 R 2  is hydrogen;   R 3A  and R 3B  are selected from substituted or unsubstituted alkylene, substituted or unsubstituted cycloalkylene, and substituted or unsubstituted arylene;   each occurrence of E 3  to E 6  is NR 4 ;   R 4  is selected from hydrogen, or optionally substituted alkyl or heteroalkyl;   each X is the same, and is selected from OC(O)R x , OR x , or OSO 2 R x , R x  is alkyl, alkenyl, alkynyl, heteroalkyl, aryl, heteroaryl or alkylaryl;   M 1  and M 2  are independently selected from Mg(II), Ni(III), Ni(III)-X Co(II), Co(III)-X and Zn(II), and wherein:   (i) R 3A  is different from R 3B ; and/or   (ii) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 .   
     
     
         29 . The catalyst of  claim 1 , wherein both occurrences of R 1  are the same, and are tertiary butyl;
 R 2  is hydrogen;   R 3A  and R 3B  are selected from tertiary butylene, benzylene, ethylene, propylene, 2,2-dimethylpropylene;   each occurrence of E 3  to E 6  is NR 4 ;   R 4  is selected from hydrogen, methyl, ethyl, propyl, butyl, or -alkyl-C(O)—OR 19 ;   each X is the same, and is OAc;   M 1  and M 2  are independently selected from Mg(II), Ni(II), Co(II), Co(III)-X, Ni(III)-X and Zn(II), and wherein:   iii) R 3A  is different from R 3B ; and/or   iv) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 .   
     
     
         30 . The catalyst of  claim 1 , of the formula: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         31 . The catalyst of  claim 1  of the formula: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
     
     
         32 . A ligand of formula (II): 
       
         
           
           
               
               
           
         
       
       wherein:
 R 1  and R 2  are independently selected from hydrogen, halide, a nitro group, a nitrile group, an imine, an amine, an ether group, a silyl group, a silyl ether group, a sulfoxide group, a sulfonyl group, a sulfinate group or an acetylide group or an optionally substituted alkyl, alkenyl, alkynyl, haloalkyl, aryl, heteroaryl, alkoxy, aryloxy, alkylthio, arylthio, alicyclic or heteroalicyclic group; 
 R 3A  and R 3B  are independently selected from optionally substituted alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene, arylene, heteroarylene or cycloalkylene, wherein alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene and heteroalkynylene, may optionally be interrupted by aryl, heteroaryl, alicyclic or heteroalicyclic; 
 R 5  is independently selected from H, or optionally substituted aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl, heteroaryl, alkylheteroaryl or alkylaryl; 
 E 1  is C, E 2  is OY, S or NH or E 1  is N and E 2  is OY; 
 Y is hydrogen or an alkali metal; 
 E 3 , E 4 , E 5  and E 6  are each independently selected from N, NR 4 , O and S, wherein when any of E 3 , E 4 , E 5  or E 6  are N,   is  , and wherein when any of E 3 , E 4 , E 5  or E 6  are NR 4 , O or S,   is  ; 
 R 4  is independently selected from H, or optionally substituted aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl, heteroaryl, alkylheteroaryl or alkylaryl; and wherein:
 (i) R 3A  is different from R 3B ; and/or 
 (ii) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 . 
 
 
     
     
         33 . The ligand of  claim 32 , wherein both occurrences of R, are the same, and are selected from hydrogen, halide, amino, nitro, sulfoxide, sulfonyl, sulfinate, silyl, silyl ether and an optionally substituted alkyl, alkenyl, aryl, heteroaryl, alkoxy, aryloxy or alkylthio;
 R 2  is hydrogen;   R 3A  and R 3B  are selected from substituted or unsubstituted alkylene, substituted or unsubstituted cycloalkylene and substituted or unsubstituted arylene;   E 3  to E 6  are N, NR 4 , S or O;   R 4  is selected from hydrogen, or optionally substituted alkyl or heteroalkyl;   
       and wherein:
 i) R 3A  is different from R 3B ; and/or 
 ii) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 . 
 
     
     
         34 . The ligand of  claim 32  wherein both occurrences of R 1  are the same, and are selected from an optionally substituted alkyl;
 R 2  is hydrogen; 
 R 3A  and R 3 , are selected from substituted or unsubstituted alkylene, substituted or unsubstituted cycloalkylene, and substituted or unsubstituted arylene; 
 each occurrence of E 3  to E 6  is NR 4 ; 
 R 4  is selected from hydrogen, or optionally substituted alkyl or heteroalkyl; and wherein: 
 iii) R 3A  is different from R 3B ; and/or 
 iv) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 . 
 
     
     
         35 . The ligand of  claim 32 , wherein both occurrences of R 1  are the same, and are tertiary butyl;
 R 2  is hydrogen;   R 3A  and R 3 , are selected from butylene, benzylene, ethylene, propylene, 2,2-dimethylpropylene;   each occurrence of E 3  to E 6  is NR 4 ;   R 4  is selected from hydrogen, methyl, ethyl, propyl, butyl, or -alkyl-C(O)—OR 19 ; and wherein:   i) R 3A  is different from R 3B ; and/or   ii) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 .   
     
     
         36 . The ligand of  claim 32  of the formula: 
       
         
           
           
               
               
           
         
       
       wherein:
 R 1  is tertiary butyl; 
 R 2  is hydrogen; 
 R 3  is 2,2-dimethylpropylene; and 
 R 4  is selected from methyl, ethyl, propyl, or butyl; 
 
       or: 
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       wherein:
 R 3  is selected from 2,2-dimethylpropylene, propylene, or ethylene; 
 
       or: 
       
         
           
           
               
               
           
         
       
       wherein:
 R is methyl or hydrogen; 
 
       or: 
       
         
           
           
               
               
           
         
       
       wherein:
 R 1  is tertiary butyl; R 2  is hydrogen; R 3  is 2,2-dimethylpropylene; and R 4  is methyl, ethyl, propyl, or butyl. 
 
     
     
         37 . The ligand of  claim 32 , wherein the ligand comprises at least one N-substituent, and is selected from: 
       
         
           
           
               
               
           
         
       
       wherein: 
       R 1  is tertiary butyl; 
       R 2  is hydrogen; 
       R 3  is 2,2-dimethylpropylene; and 
       R 4  is selected from methyl, ethyl, propyl, or butyl; 
       or 
       
         
           
           
               
               
           
         
         wherein 
         R 1  is tertiary butyl; 
         R 2  is hydrogen; 
         R 3  is 2,2-dimethylpropylene; and 
         R 4  is methyl, ethyl, propyl, or butyl. 
       
     
     
         38 . A process of asymmetric N-substitution of a symmetrical ligand having a tetraaminophenol coordination sphere, the process comprising the following steps:
 c) Protecting at least two of the amino groups of the coordination sphere of the symmetrical ligand with an optionally substituted alkylene;   d) asymmetrically N-substituting one or more of the protected amino groups of the product of step (a) with a substituent.   
     
     
         39 . The process according to  claim 39 , wherein step (a) comprises reacting the symmetrical ligand with a protecting reagent comprising an optionally substituted alkylene group. 
     
     
         40 . The process according to  claim 39 , wherein step (a) comprises protecting the amino groups of the coordination sphere of the symmetrical ligand by forming bridging groups between the adjacent amino groups or amino and phenolic groups. 
     
     
         41 . The process according to  claim 39 , wherein step (b) comprises asymmetrically N-substituting one or more of the protected amino groups of the product of step (a) with an N-substituting agent. 
     
     
         42 . The process according to  claim 42 , wherein the N-substituting agent is an alkylating agent or an alkene. 
     
     
         43 . The process according to  claim 39 , wherein the process further comprises step (c) hydrolysing the optionally substituted alkylene bridging groups between the adjacent amino groups. 
     
     
         44 . The process according to  claim 39 , wherein the asymmetrical ligand is formula (II): 
       
         
           
           
               
               
           
         
       
       wherein:
 R 1  and R 2  are independently selected from hydrogen, halide, a nitro group, a nitrile group, an imine, an amine, an ether group, a silyl group, a silyl ether group, a sulfoxide group, a sulfonyl group, a sulfinate group or an acetylide group or an optionally substituted alkyl, alkenyl, alkynyl, haloalkyl, aryl, heteroaryl, alkoxy, aryloxy, alkylthio, arylthio, alicyclic or heteroalicyclic group; 
 R 3A  and R 3B  are independently selected from optionally substituted alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene, heteroalkynylene, arylene, heteroarylene or cycloalkylene, wherein alkylene, alkenylene, alkynylene, heteroalkylene, heteroalkenylene and heteroalkynylene, may optionally be interrupted by aryl, heteroaryl, alicyclic or heteroalicyclic; 
 R 5  is independently selected from H, or optionally substituted aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl, heteroaryl, alkylheteroaryl or alkylaryl; 
 E 1  is C, E 2  is OY, S or NH or E 1  is N and E 2  is OY; 
 Y is hydrogen or an alkali metal; 
 E 3 , E 4 , E 5  and E 6  are each independently selected from N, NR 4 , O and S, wherein when any of E 3 , E 4 , E 5  or E 6  are N,   is  , and wherein when any of E 3 , E 4 , E 5  or E 6  are NR 4 , O or S,   is  ; 
 R 4  is independently selected from H, or optionally substituted aliphatic, heteroaliphatic, alicyclic, heteroalicyclic, aryl, heteroaryl, alkylheteroaryl or alkylaryl; and wherein:
 (i) R 3A  is different from R 3B ; and/or 
 (ii) at least one occurrence of E 3 , E 4 , E 5  and E 6  is different to a remaining occurrence of E 3 , E 4 , E 5  and E 6 , and wherein the ligand comprises at least one N-substituent, and is selected from: 
 
 
       
         
           
           
               
               
           
         
       
       wherein: 
       R 1  is tertiary butyl; 
       R 2  is hydrogen; 
       R 3  is 2,2-dimethylpropylene; and 
       R 4  is selected from methyl, ethyl, propyl, or butyl; 
       or 
       
         
           
           
               
               
           
         
         wherein 
         R 1  is tertiary butyl; 
         R 2  is hydrogen; 
         R 3  is 2,2-dimethylpropylene; and 
         R 4  is methyl, ethyl, propyl, or butyl. 
       
     
     
         46 . A process for the reaction of:
 (i) carbon dioxide with an epoxide;   (ii) an epoxide and an anhydride; and/or   (iii) a lactide and/or a lactone,   in the presence of the catalyst of  claim 1 , optionally wherein the process is carried out in the presence of a chain transfer agent.   
     
     
         47 . The process of  claim 46 , wherein the process is carried out in a continuous flow reactor, or a batch reactor. 
     
     
         48 . The process of  claim 47 , wherein the reaction is carried out in a continuous flow reactor.