Preparation, Reaction, and Catalysis of the New Ruthenium Carbamato Complex Et₂NCO₂RuH(CO)(PCy₃)₂

CO₂ promoted the RuCl₃·3H₂O-catalyzed dimerization of phenylacetylene (2) in the presence of PR₃ (R = Bu, Cy) and Et₂NH to afford 1,4-diphenyl-1-buten-3-yne (3). Et₂NCO₂RuH(CO)(PCy₃)₂ (4) and (PhC⋮C)₂Ru(CO)(PCy₃)₂ (5) were isolated by the RuCl₃·3H₂O/PCy₃/Et₂NH/CO₂ and 4/2 reactions, respectively, and catalyzed the dimerization of 2 to afford 3 with the concomitant formation of a poly(phenylacetylene).