Preparation and thermolysis of complexes derived from some trinuclear ruthenium clusters and 1,4-diphenylbuta-1,3-diyne

Reactions between Ru-3(mu-dppm)(CO)(10) and PhC=CC=CRh in thf, in the presence of Me3NO, afford the complexes Ru-3(mu(3)-PhC2C=CPh)(mu-dppm)(mu-CO)(CO)(7) (1) and Ru-3(mu-dppm)(mu-C4Ph2(C=CPh)(2))(CO)(6) (2). Complex 1 was also obtained from Ru-3(mu(3)-PhC2C=CPh)(mu-CO)(CO)(9) (3) and dppm in thf on heating. Two of the complexes formed by thermolysis of 1 in xylene at 130 degrees C were identified crystallographically as Ru-3{mu(3)-CPhCHCC(C6H4-2)}(mu-dppm)(CO)(8) (4) and Ru-3(mu(3)-C4H2Ph2)(mu-CO)(CO)(5)(dppm) (5). In 4, fragmentation of the cluster and metallation of one of the diyne phenyl groups took place; the dppm ligand bridges two non-bonded Ru atoms. In 5, partial hydrogenation of the diyne has occurred to give a 2 eta(1):eta(4):eta(4)-butadiendiyl ligand, the dppm ligand adopting a chelating mode on one of the two Ru atoms which is eta 4 attached to the hydrocarbon. In comparison, thermolysis of 3 gave Ru-4(mu(4)-PhC2C=CPh)(CO)(n) (n = 12 (6) and 14 (7)). The former has a distorted C2Ru4 octahedral core, while in the latter the Ru-3 cluster has fragmented to give a ruthenacyclopentadiene derivative in which the central C-C bond bridges an Ru-2(CO)(8) group. (C) 1997 Elsevier Science S.A.