TECHNETIUM CARBON MULTIPLE BONDS - SYNTHESIS AND STRUCTURE OF TC(=C=CHPH)CL(DPPE)2 AND [TC(EQUIVALENT-TO-C-CH2-T-BU)CL(DPPE)2]+

The 16-electron complex TcCl(dppe)2 reacts with terminal alkynes to form neutral vinylidene complexes of the type Tc(=C=CHR)Cl(dppe)2 (R = Ph, Me, t-Bu). Treatment of these vinylidene complexes with acid (HBF4 for R = Ph, HNMe3BPh4 for R = t-Bu) yields the respective terminal carbyne complexes Tc(=CCH2R)Cl(dppe)2+ (R = Ph, t-Bu). These vinylidene and carbyne compounds represent the first examples of technetium carbenes or carbynes. X-ray structures of Tc(=C= CHPh)Cl(dppe)2 and Tc(=CCH2-t-Bu)Cl(dppe)2+ were determined, and the Tc-C bond lengths obtained were 1.861(9) and 1.724(7) angstrom, respectively.