REACTIONS OF DISUBSTITUTED BUTADIYNES WITH TITANOCENE COMPLEXES

The mode of the reaction of titanocene ''Cp2Ti'' with disubstituted butadiynes RC=C C=CR' depends strongly on the nature of the substituents R and R'. For R = R' = SiMe3 the starting butadiyne is split by titanocene to yield the dinuclear complex [Cp2Ti(C=CSiMe3)]2 (1). For other symmetrically substituted (R = R'= Ph or (t)Bu) or unsymmetrically substituted butadiynes (R = SiMe3, R' = Ph or R = SiMe3, R' = (t)Bu) the reaction proceeds to dinuclear complexes with a central 1,4-disubstituted mu-eta(1-3),eta(2-4)-trans,trans-butadiene unit (''zig-zag-butadiyne'') between the two titanium centres (R = R' = (t)Bu (2); R = SiMe3, R'= (t)Bu (3a); R = SiMe3, R' = Ph (3b)). Complexes 2 and 3a were characterized by X-ray structure analyses.