Ruthenium catalyzed homocoupling of terminal alkynes

Several complexes of the type RuTp(L)(L')Cl (L, L' = P, N, O donors) were tested with respect to their ability of promoting catalytic C-C-coupling reactions of terminal acetylenes. When L = tertiary phosphine, predominantly dimerization occurs, RuTp(PPh3)(2)H being the most efficient pre-catalyst. In the absence of a phosphine ligand, polymerization takes place with RuTp(COD)CI as the most effective pre-catalyst. Both product distribution and conversion depend strongly on the substituent of the alkyne and to a lesser extent on the co-ligands of the ruthenium complex. The catalytically active species is the 16e(-) alkynyl complex RuTp(L)(-C=C-R) which in case of L = PCy3 and R = Bu " could be trapped as RuTp(PCy3)(-C-CBu ")(CO).