Group 3 post-metallocene complexes based on bis(naphthoxy)pyridine and bis(naphthoxy)thiophene ligands for the ring-opening polymerisation of polar cyclic monomers

1. A process for preparing homo-or co-polymers of polar cyclic monomers by ring-opening polymerisation with a metallic complex of formula I:

wherein R 1 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently selected from hydrogen, an unsubstituted or a substituted hydrocarbyl, or an inert functional group, wherein two or more of R 1 , R 3 , R 4 , R 5 , R 6 and R 7 can be linked together to form one or more rings;

wherein Z′ is one or two heteroatom(s) and n is 0 or 1;

wherein Z is an atom selected from Group 14 of the Periodic Table;

wherein R 2 is an alkyl or a substituted or an unsubstituted aryl group having at most 8 carbon atoms with the restriction that Z(R 2 ) 3 is a bulky group that is at least as bulky as tert-butyl, and wherein Z(R 2 ) 3 can be a substituted aryl group;

wherein M is a metal of Group 3 of the periodic Table or a member of the lanthanide series; and

wherein R $ is an alkyl, CH 2 SiMe 3 , CH(SiMe 3 ) 2 , OR*, or NR ** 2 , wherein R * is alkyl, aryl or lactate O-CH(CH 3 )(COOR′), and wherein R ** is SiMe 3 or SiHMe 2 .

2. The process of claim 1 , wherein R 1 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently selected from hydrogen or alkyl groups having at most 6 carbon atoms.

3. The process of claim 1 , wherein Z′ is S or N.

4. The process of claim 1 , wherein Z is C or Si.

5. The process of claim 1 , wherein R 2 is a substituted or an unsubstituted phenyl group or a higher aromatic group.

6. The process of claim 1 , wherein R 5 is N(SiHMe 2 ) 2 , N(SiMe 3 ) 2 or OiPr.

7. The process of claim 1 , wherein the polar cyclic monomers are selected from lactides, beta-butyrolactone, or 5- or 6- membered cyclic carbonates selected from trimethylenecarbonate (TMC), 2-benzyloxy-trimethylenecarbonate (BTMC), 2-hydroxy-trimethylenecarbonate (TMCOH), 4-(benzyloxymethyl)-1,3-dioxolan-2-one (BDMC), 4-(hydroxymethyl)-1,3-dioxolan-2-one (DMCOH), 2-oxy-trimethylenecarbonate (OTMC), dehydrotrimethylenecarbonate (DHTMC), or a combination thereof.