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The crystal structure of (η6-C6Me6)Ti[(μ-Cl)2(AlClEt)]2 and the catalytic activity of the (C6Me6)TiAl2Cl8−xEtx(x  04) complexes towards butadiene

1992; Elsevier BV; Volume: 430; Issue: 3 Linguagem: Inglês

10.1016/0022-328x(92)83267-l

1872-8561

S.I. Troyanov, J. Poláček, Helena Antropiusová, Karel Mach,

Coordination Chemistry and Organometallics

The composition of (C6Me6)TiAl2Cl8−xEtx complexes in (C6Me6)TiAl2Cl8 + n Et3Al (n = 0.5-6) systems was studied by UV-Vis spectroscopy and the X-ray crystal structure of one of them, (η6-C6Me6)Ti[(μ-Cl)2(AlClEt)]2 (IIa-2), has been determined. The complex crystallizes in the orthorhombic space group Pna21 with Z = 4 and lattice parameters a 15.634(3), b 11.355(2), c 14.417(2) Å. The ethyl groups of IIa-2 reside in outer positions of aluminate ligands farther away from the C6Me6 ligand. The other part of the complex does not differ remarkably from structures of other (arene)TiII complexes. Negligible activity of (C6Me6)TiAl2Cl8 towards the butadiene cyclotrimerization is considerably increased by addition of 2.5–3.0 equivalents of Et3Al. As follows from UV-Vis spectra, such systems contain mainly the (C6Me6)TiAl2Cl5Et3 complex. It is suggested that the introduction of three Et substituents destabilizes the Ti-(η6-C6Me6) bond so that the replacement of hexamethylbenzene by butadiene in the first step of a catalytic cycle becomes more feasible.