Further observations on the dimerisation of alkynes on triruthenium clusters

The reaction between Ru-3{mu(3)-PPhCH2PPh(C6H4)}(CO)(9) (2) and HC2Ph resulted in insertion of a diene formed by coupling of the alkyne into an Ru-P(phosphido) bond to give a PPh(C6H4)CH2PPh(C4H2Ph2) ligand. Thermolysis regenerated the original phosphido-phosphine ligand and the alkyne dimer, which was coordinated in the usual 2 eta(1):eta(4)-mode. Similar metallacyclopentadiene [GRAPHICS] complexes were obtained from 2 and HC2CO2Me, from Ru-3{mu(3)-RC2(CO2Me)}(mu-dppm)(mu-CO)(CO)(7) and C2Ph2[R = CO2Me, H (2 isomers)], and from [Ru-3(mu(3),-PPhCH2PPh2)(CO)(9)](-) and C2Ph2, followed by protonation. X-ray structures are reported for the complexes Ru-3{mu(3)-C2Ph2C2(CO2Me)(2)}(mu-dppm)(CO)(6) (5) and two isomers of Ru-3{mu(3)-C2Ph2 CHC(CO2Me)}(mu-dppm)(CO)(6) (8a and 8b), Ru-3{mu(3)-PPh(C6H4)CH2PPh(C4H2Ph2)}(mu-CO)(CO)(6) (9) and Ru-3(mu-H)(mu(3)-PPhCH2PPh2)(mu-C4Ph4)(CO)(6) (12). In 5, 8a and 8b, one of the ester CO groups is bonded to an Ru atom also coordinated to phosphorus. [GRAPHICS] (C) 1998 Elsevier Science S.A.