Reactions of [RhRu3H(η5-C5Me5)(CO)9 BH2] with didentate phosphines and the synthesis and crystal structure of [RhRu3H2(η5-C5Me5)(CO)8(µ-dppf-P,P′)AuB][dppf = 1,1′-bis(diphenylphosphino)ferrocene]

Abstract

Ligand-substitution reactions of [RhRu₃H(η⁵-C₅Me₅)(CO)₉ BH₂] with the didentate phosphines dppf and dppa yielded compounds of the type [RhRu₃H₂(η⁵-C₅Me₅)(CO)₈(L-P)BH][L = 1,1′-bis(diphenylphosphino)-ferrocene (dppf) or bis(diphenylphosphino)acetylene (dppa)] with the P-donor ligand replacing one CO ligand in a butterfly wingtip site. Spectroscopic data indicate that a redistribution of cluster hydrogen atoms occurs during CO ligand substitution. Subsequent reaction of [RhRu₃H₂(η⁵-C₅Me₅)(CO)₈(dppf-P)BH] with [N(PPh₃)₂]Cl and [Au₂Cl₂(dppf)] yielded [RhRu₃H₂(η⁵-C₅Me₅)(CO)₈(µ-dppf-P,P′)AuB], but there was a competitive intramolecular substitution reaction to give [RhRu₃H₃(η⁵-C₅Me₅)(CO)₇(µ-dppf-P,P′)B]. The gold cluster has been characterised by single-crystal X-ray crystallography. The RhRu₃B core is straddled by a {Au(dppf)} unit which co-ordinates to a wingtip ruthenium atom through a phosphorus atom whilst the gold centre bridges the ruthenium–boron edge. Possible routes to the formation of [RhRu₃H₂(η⁵-C₅Me₅)(CO)₈(µdppf-P,P′)AuB] have been investigated.