Phosphinic vanadium complex, catalytic system comprising said phosphinic vanadium complex and process for the (co) polymerization of conjugated dienes

A catalytic system for the (co) polymerization of conjugated dienes comprising:

• (a) at least one phosphinic vanadium complex having the general formula (I) or (II):
• V(X)3[P(R1)n(R2)3-n]2 (I)
• V(X)3[(R3)2P(R4)P(R3)2] (II)
• wherein:
• X represents a halogen anion;
• or is selected from the following groups:
• thiocyanate, isocyanate, sulfate, acid sulfate, phosphate, acid phosphate, carboxylate and dicarboxylate;
• R1, identical or different among them, represent a hydrogen atom, or an allyl group (CH2═CH—CH2—);
• or are selected from a C1-C20 alkyl group, linear or branched, and an optionally halogenated, optionally substituted cycloalkyl group;
• n is an integer ranging from 0 to 3;
• R2, identical or different among them, represent an optionally substituted aryl group;
• R3, identical or different among them, represent a hydrogen atom, or an allyl group (CH2═CH—CH2—);
• or are selected from a C1-C20 alkyl group, linear or branched, an optionally halogenated, optionally substituted cycloalkyl group, and an optionally substituted aryl group;
• R4 represents a group —NR5 wherein R5 represents a hydrogen atom, or is a C1-C20 alkyl group, linear or branched;
• or R4 represents an alkylene group
• —(CH2) p- wherein p represents an integer ranging from 1 to 5;
• provided that in the general formula (I), in case n is equal to 1 and R1 is methyl, R2 is different from phenyl;
• (b) at least one co-catalyst selected from the following organo-derivatives of aluminum:
• (b1) an aluminum compound having general formula (III):
• Al(R6)(R7)(R8) (III)
• wherein R6 represents a hydrogen atom, or a fluorine atom, or is selected from a C1-C20 alkyl group, linear or branched, a cycloalkyl group, an aryl group, an alkylaryl group, an arylalkyl group, and an alkoxy group;
• R7 and R8, identical or different among them, are selected from a C1-C20 alkyl group, linear or branched, a cycloalkyl group, an aryl group, an alkylaryl group, and an arylalkyl group;
• (b2) an aluminoxane having general formula (IV):
• (R9)2—Al—O—[—Al(R10)—O-]q-Al—(R11)2 (IV)
• wherein R9, R10 and R11, identical or different among them, represent a hydrogen atom, or a halogen atom;
• or are selected from a C1-C20 alkyl group, linear or branched, a cycloalkyl group, and an aryl group, said groups being optionally substituted with one or more atoms of silicon or germanium;
• and q is an integer ranging from 0 to 1000;
• (b3) an organo-derivative compound of aluminum partially hydrolyzed;
• (b4) a halogen aluminum alkyl having general formula (V) or (VI):
• Al(R12)n(X1)3-n (V)
• Al2(R12)m(X1)6-m (VI)
• wherein n is 1 or 2;
• m is an integer ranging from 1 to 5;
• R12, identical or different among them, are selected from a C1-C20 alkyl group, linear or branched;
• X1 represents a chlorine or bromine atom;
• or mixtures thereof.