Bimetallic catalytic complexes for the polymerisation of carbon dioxide and an epoxide

A dimeric catalyst wherein said dimeric catalyst comprises two monomeric subunits, wherein each monomeric subunit is a catalyst of formula (I):

• wherein each R1 and R2 are independently hydrogen, alkyl, haloalkyl, aryl, halide, amine, a nitro group, an ether group, a silyl ether group, a nitrile group or an acetylide group;
• each R3 is independently alkylene, arylene or cycloalkylene;
• each R4 is independently H, alkyl, aryl or alkylaryl;
• each E1 is C, each E2 is independently O, S or NH;
• or each E1 is N and each E2 is O;
• X is OCOCH3, OCOCF3, OSO2C7H7, OSO(CH3)2 or halide;
• M is Zn(II), Cr(II), Co(II), Mn(II), Mg (II), Fe(II), Cr (III)—X, Co (III)—X, Mn (III)—X or Fe(III)—X;
• and wherein the two monomeric subunits are linked by a bridging ligand X.