SERENDIPITOUS SYNTHESIS OF OHEXADIENYL]-(ETA(5)-CYCLOPENTADIENYL)TITANIUM(II) AND ITS 4-ALKYL DERIVATIVES

The titanium-magnesium complex -eta(2):eta(2)-C-2(SiMe(3))(2)](2)[(eta (5)-C-5)Mg] (1) containing perpendicularly bridging bis(trimethylsilyl )acetylene ligands reacts with excess (trimethylsilyl)ethyne to give m ainly ohexadeinyl)-(eta(5)-cyclopentadienyl)titanium(II) (2). The X-ra y crystal structure of 2 showed that the SiMe(3) group at C(6) is in e xo-position and the Cp ring and of the dienyl part of the Chx ring are nearly parallel. The dihedral angle 4.9 degrees between these planes is mainly due to tilting of the cyclohexadienyl ring by the C(1) and C (5) side toward the titanium atom. Analogous reactions of 1 with tert- butylethyne, cyclohexylethyne, 1-hexyne, and phenylethyne afforded loh exadienyl)(eta(5)-cyclopentadienyl)titanium(II) derivatives 3-6 contai ning the 1-alkyne substituent at C(4).