Alkyne-coupling reactions catalyzed by OsHCl(CO)((PPr3)-Pr-i)(2) in the presence of diethylamine

Complex OsHCl(CO)((PPr3)-Pr-i)(2), in the presence of diethylamine, catalyz es the dimerization of terminal alkynes HC=CR (R = Me3C, Cy, Ph, and Me3Si) . The reactions initially give butatrienes RCH=C=C=CHR, which are stable un der the reaction conditions for R = Me3C and Cy. For R = Ph, the butatriene s polymerize to -[CH(Ph)C drop CCH(Ph)](n)-, while for R = Me3Si, the butat riene isomerizes into the enyne Z-Me3SiCH=CH-C drop CSiMe3. The formation o f butatrienes takes place via butenynyl intermediates of the type Os(C drop CR){eta (3)-C(C drop CR)=CHR}(CO) ((PPr3)-Pr-i)(2).