Reactions of ruthenium(O) phosphine complexes with diphenylacetylene

Heating diphenylacetylene with [Ru(CO)2(PPh3) 3] in toluene under reflux provides the 2-phenylindenone complex [Ru(η3=CCPh=CHC6H4)(CO)(PPh 3)2], arising from C-H activation of one ortho-proton of diphenylacetylene, hydroruthenation of the triple bond, and cyclization incorporating one carbonyl ligand. Both phosphines are replaced by 1,2-bis-(diphenylphosphino)ethane to provide [Ru(η4-O=CCPh= CHC6H4)(CO)(dppe)]. In contrast, heating diphenylacetylene with [Ru(CO)3(PPh3)2] in toluene under reflux generates the tetraphenylcyclopentadienone complex [Ru(η4-C)= CC4Ph4)(CO)2(PPh3)] in high yield, via [2+2+1] alkyne and CO cyclization. The crystal structures of [Ru(η44-O=CCPh=CHC6H4)-(CO)(PPh 3)2], [Ru(η4-O=CCPh=CHC6H 4)(CO)(dppe)], [Ru(η4-O=CC4Ph 4)(CO)2(PPh3)], and [Ru(η-PhC=CPh)(CO) 2(PPh3)2] solvates are reported.