Catalysts and processes for stereoselective ring-opening polymerization

A process for the preparation of a chelate complex which comprises a step of reacting a rare earth metal precursor comprising a rare earth metal cation M with one of b1 or b2

• b1) a pro-ligand of formula (PL1A) or a deprotonated form thereof from which the protons of the phenolic hydroxyl groups shown in formula (PL1A) are removed:
• b2) a pro-ligand of formula (PL1B) or a deprotonated form thereof from which the protons of the phenolic hydroxyl groups shown in formula (PL1B) are removed:
• wherein, in formulae (PL1A) and (PL1B),
• R1a and R1b independently represent a sterically demanding group comprising 6 or more skeleton atoms, and optionally, R1a and R1b may be linked to each other to provide a divalent organic residue,
• R2a and R2b are independently selected from hydrogen, C1-C20 alkyl, halogen, —NO2, —CN, C1-C10 haloalkyl, C1-C10 alkoxy, aryloxy with a 6 to 10 membered aryl group which is optionally substituted, heteroaryloxy with a 5 to 10 membered heteroaryl group which is optionally substituted, C2-C5 alkenyl, C2-C5 alkynyl, a 6 to 10 membered aryl group which is optionally substituted, a 5 to 10 membered heteroaryl group which is optionally substituted, —NRS9RS10 where RS9 and RS10 are independently selected from C1-C5 alkyl, a group of the formula (S-1)
• wherein RS1 is selected from a C1-C9 divalent alkyl group which is optionally substituted, —O— and a —O—C1-C8 divalent alkyl group which is optionally substituted, and RAR1 is selected from a phenyl group which is optionally substituted and a 5- to 6-membered heteroaryl group which is optionally substituted, and
• a group of the formula (S-2)
• wherein RS2 is selected from a C1-C6 trivalent alkyl group which is optionally substituted, —O— and a —O—C1-C5 trivalent alkyl group which is optionally substituted, and RAR2 and RAR3 are independently selected from a phenyl group which is optionally substituted and a 5- to 6-membered heteroaryl group which is optionally substituted,
• R3a and R3b are, independently for each occurrence, selected from hydrogen, C1-C10 alkyl, halogen, —NO2, —CN, C1-C10 haloalkyl, C1-C10 alkoxy, aryloxy with a 6 to 10 membered aryl group which is optionally substituted, heteroaryloxy with a 5 to 10 membered heteroaryl group which is optionally substituted, C2-C5 alkenyl, C2-C5 alkynyl, a 6 to 10 membered aryl group which is optionally substituted, a 5 to 10 membered heteroaryl group which is optionally substituted, and —NRS9RS10 where RS9 and RS10 are independently selected from C1-C5 alkyl,
• R4a and R4b are selected, independently for each occurrence, from hydrogen, C1-C3 alkyl, halogen, —NO2, —CN, C1-C3 haloalkyl and C1-C3 alkoxy,
• R5a and R5b are independently selected from hydrogen, alkyl, cycloalkyl and phenyl, with the proviso that one of R5a and R5b must be hydrogen,
• R6 is selected from a C2-C5 alkanediyl, a C2-C5 alkenediyl and a C2-C5 alkynediyl group,
• wherein, in the alkanediyl, alkenediyl and alkynediyl group 1 or 2 carbon atoms may be replaced with a heteroatom selected from O and N,
• and wherein any hydrogen atom in the alkanediyl, alkenediyl and alkynediyl group may be replaced by a substituent RS11, wherein RS11 is selected, independently for each occurrence, from C1-C20 alkyl, halogen, —NO2, —CN, C1-C10 haloalkyl, C1-C10 alkoxy, aryloxy with a 6 to 10 membered aryl group which is optionally substituted, heteroaryloxy with a 5 to 10 membered heteroaryl group which is optionally substituted, C2-C5 alkenyl, C2-C5 alkynyl, a 6 to 13 membered aryl group which is optionally substituted, a 5 to 10 membered heteroaryl group which is optionally substituted, and —NRS9RS10 where RS9 and RS10 are independently selected from C1-C5 alkyl,
• and/or two substituents RS11 may be linked to form, together with the atoms to which they are attached, a 5 to 14 membered carbocyclic or heterocyclic group which is optionally substituted by one or more further substituents;
• to form a chelate complex.