ИСТИНА

Racemic complex of formula (I) ** (See formula) ** in which M is zirconium or hafnium; each X is a sigma ligand; L is a divalent bridge selected from -R'2C-, -R'2C-CR'2-, -R'2Si-, -R'2Si-SiR'2-, -R'2Ge-, in which each R 'is independently a hydrogen atom, C1-20 hydrocarbyl, tri (C1-20 alkyl) silyl, C6-20 aryl, C7-20 arylalkyl or C7-20 alkylaryl; R2 and R2 'are each independently a C1-20 hydrocarbyl radical optionally containing one or more heteroatoms of groups 14-16; R5 'is Z'R3' in which Z 'is O or S; and R3 'is a C1-10 hydrocarbyl group; R6 and R6 'are each independently hydrogen or a C1-20 hydrocarbyl group optionally containing one or more heteroatoms of groups 14-16; R7 and R7 'are each independently hydrogen or a C1-20 hydrocarbyl group optionally containing one or more heteroatoms of groups 14-16; Ar is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted with one or more R1 groups; Ar 'is independently an aryl or heteroaryl group having up to 20 carbon atoms optionally substituted with one or more R1 groups; each R1 is a C1-20 hydrocarbyl group or two R1 groups in adjacent carbon atoms taken together can form a condensed non-aromatic ring of 5 or 6 members with the Ar group, said ring being optionally substituted with one or more R4 groups; and each R4 is a C1-20 hydrocarbyl group.