TITANOCENE-BIS(TRIMETHYLSILYL) ACETYLENE COMPLEXES - EFFECTS OF METHYL SUBSTITUENTS AT THE CYCLOPENTADIENYL LIGANDS ON THE STRUCTURE OF THERMOLYTIC PRODUCTS

The (C(5)H5-nMe(n))(2)Ti[eta(2)-C-2(SiMe(3))(2)] (n = 0-5) (1A-1F) com plexes were prepared by the reduction of corresponding titanocene dich lorides with magnesium in THF in the presence of bis(trimethylsilyl)ac etylene (BTMSA). All of them were characterized by spectroscopic metho ds and (C(5)HMe(4))(2)Ti[eta(2)-C-2(SiMe(3))(2)] (1E) by the X-ray cry stal analysis. The complexes decompose at temperatures in the range 10 0-200 degrees C. Those with n = 0-3 yield di-mu-hydrido)bis(eta(5)-cyc lopentadienyltitanium) (2A) and its methylated analogues (2B-2D) where as BTMSA is released. The crystal structure of 2D showed that the hexa methylfulvalene ligand contains non-methylated carbon atoms in inner a lternate positions. Complex 1E afforded a mixture of products. Among t hem only volatile isomers pentenyl)(eta(5)-tetramethylcyclopentenyl)ti tanium (2Ea) and (eta 3:eta 4-1,3-dimethyl-4, tenyl)(eta(5)-tetramethy lcyclopentadienyl)titanium (2Eb) have been so far isolated as minor pr oducts. The C(5)Me(5) complex 1F yields quantitatively yclopentenyl)(p entamethylcyclopentadienyl)titanium (2F) and BTMSA is hydrogenated to a mixture of cis- and trans-bis(trimethylsilyl)ethene.