Synthesis and Reactions with Carbon Dioxide of Mono(#sigma#-alkynyl) Titanocene(III) Complexes Cp_2~*Ti(C ident to CR) (R = Me, t-Bu) and the Corresponding 'Ate' Complexes [Cp_2~*Ti(C ident to CRo)_2LI(THF)_n] (R = SiMe_3, t-Bu, Ph)

摘要

The reactions of the titanium(III) complex Cp_2~*TiCl with lithium acetylides RC ident to CLi depend strongly on the solvents used. In THF only the lithium tweezer compounds [Cp_2~*Ti(C ident to CR)_2Li(THF)_n] (Cp~* = #eta#~5-C_5Me_5; R = SiMe_3, n = 1(1); R = t-Bu, n = 1(2); r = pH, n = 2(3)), not the expected mono(#sigma#-alkynyl) titanocene(III) complexes, were obtained, whereas in n-hexane these complexes Cp_2~*Ti(C ident to CR) wereisolated for R = Me (4), t-Bu (5). The reaction of the complex [Cp_2~*Ti(C ident to CSiMe_3)_2Li(THF)] (1) with carbon dioxide results in the titnafuranone 6, which presumably is formed by insertion of carbon dioxide into the #eta#~2-butadiyne complex Cp_2~*Ti(#eta#~2-Me_3SiC ident to CC ident to SCiMe_3). The complex [Cp_2~*Ti(C ident to C-t-Bu)_2Li(THF)] (2) reacts with carbon dioxide to yield the permethyltitanocene carboxylate Cp_2~*Ti(O_2CC ident to C-t-Bu) (7) via insertion into the #sigma#-acetylide bond of the in situ formed titanium(III) intermediate [Cp_2~*Ti(C ident to CPhI)_2Li(THF)_2] (3) with carbon dioxide gives the stable bis(#sigma#-acetylide) permethyltitanocene Cp_2~*Ti(C ident to CPh_2) (8) without coupling of the #sigma#-acetyide groups (as four for 1) and without insertion into the #sigma#-acetylide bond (as found for 2). The syntheses and reactions of these compounds are compared to those of similar complexes of unsubstituted titanocene compounds. Complexes 1, 5, and 7 were investigated by X-ray crystal structure analysis.