Compounds of the rare earths and their use as polymerization catalysts for unsaturated compounds

A catalyst comprising allyl complexes of the rare earths of formula (I)

• [(C3R15)rM1(X)2−r(D)n]⊕[M2(X)p(C6H5−qR2q)4−p]⊖ (I)
• wherein:
• M1 denotes a trivalent element of the rare earths of atomic numbers 21, 39, 57 to 71, X is the same or different and denotes an anion, D is the same or different and denotes a neutral donor ligand, M2 represents an element of group IIIb of the periodic table of the elements, R1 is the same or different and represents hydrogen, a linear or branched, saturated or singly- or multiply-unsaturated C1-C30 alkyl radical or C5-C30 cycloalkyl radical which may optionally contain one or more hetero atoms a C6-C30 aryl radical which may optionally contain one or more hetero atoms, which is optionally singly- or multiply-substituted by alkyl, alkynyl or alkenyl radicals comprising 1 to 30 carbon atoms or by phenyl groups comprising 6 to 30 carbon atoms and which can be condensed with other aromatic compounds containing 6 to 30 carbon atoms, or represents a silyl group which is substituted by alkyl, alkenyl or alkynyl groups comprising 1 to 30 carbon atoms or by phenyl groups comprising 6 to 30 carbon atoms, R2 is the same or different and represents a fluorine atom or a fluoroalkyl group comprising 1 to 10 carbon atoms, n represents an arbitrary number from 0 to 10, p represents an arbitrary number from 0 to 3, q represents an arbitrary number from 1 to 5, r represents an arbitrary number from 1 to 2.