Method for producing high melting-point polyolefins

A process for the preparation of a high-melting polyolefin by homo- or copolymerization of one or more monomers from the group consisting of α-olefins having 2 or more C atoms in the presence of an organometallic catalyst which can be activated by a cocatalyst, which comprises employing as the organometallic catalyst a metallocene compound or π complex compound of the formula

• in which
• CpI and CpII are two identical or different carbanions having a cyclopentadienyl-containing structure, in which one to all the H atoms can be substituted by identical or different radicals from the group consisting of linear or branch C1-C20-alkyl, which can be monosubstituted to completely substituted by halogen, mono- to trisubstituted by phenyl or mono- to trisubstituted by vinyl, C6-C12-aryl, halogenoaryl having 6 to 12 C atoms, organometallic substituents, including silyl, trimethylsilyl or ferrocenyl, or one or two can be replaced by D and A,
• D denotes a donor atom, which can additionally carry substituents and has at least one free electron pair in its bond state,
• A denotes an acceptor atom, which can additionally carry substituents and has an empty orbital capable of accepting a pair of electrons in its bond state,
• wherein D and A are linked by a reversible coordinate bond such that the donor group assumes a positive charge and the acceptor group assumes a negative charge,
• M represents a transition metal of sub-group III, IV, V or VI of the Periodic Table of the Elements, including the lanthanides and actinides,
• X denotes one anion equivalent and
• n denotes the number zero, one, two, three or four, depending on the charge of M,
• or
• a π complex compound, or metallocene compound of the formula
• in which
• πI and πII represent different charged or electrically neutral π systems which can be fused with one or two unsaturated or saturated five- or six-membered rings,
• D denotes a donor atom, which is a substituent of πI or part of the π system of πI and has at least one free electron pair in its bond state,
• A denotes an acceptor atom, which is a substituents of πII or part of the π system of πII and has an empty orbital capable of accepting a pair of electrons in its bond state,
• wherein D and A are linked by a reversible coordinate bond such that the donor group assumes a positive charge and the acceptor group assumes a negative charge, and where at least one of D and A is part of the associated π system,
• wherein D and A in their turn can carry substituents,
• wherein each π system and each fused-on ring system can contain one or more D or A or D and A and
• wherein πI and πII in the non-fused or in the fused form, one to all the H atoms of the π system independently of one another can be substituted by identical or different radicals from the group consisting of linear or branched C1-C20-alkyl, which can be monosubstituted to completely substituted by halogen, mono- to trisubstituted by phenyl or mono- to trisubstituted by vinyl, C6-C12-aryl, halogenoaryl having 6 to 12 C atoms, organometallic substituents, including silyl, trimethylsilyl or ferrocenyl, or one or two can be replaced by D and A, so that the reversible coordinate D→A bond (i) is formed between D and A which are both parts of the π system or the fused-on ring system, or (ii) of which D or A is part of the π system and in each case the other is substituent of the non-fused π system or the fused-on ring system, or (iii) both D and A are such substituents, and in the case of (iii) at least one additional D or A or both is (are) parts of the π system or the fused-on ring system,
• M and X have the above meanings and
• n denotes the number zero, one, two, three or four, depending on the charges of M and those of π-I and π-II.