Triphenylphosphine-substituted triruthenaborane clusters: a route to [Ru3(CO)9–x(PPh3)xBH5](x= 1–3)via systematic cluster degradation. Molecular structures of [Ru3H(CO)8-(PPh3)(B2H5)] and [Ru3(CO)6(PPh3)3BH5]·CH2Cl2

Abstract

Photolysis of a mixture of [Ru₃H(CO)₉(B₂H₅)] and PPh₃ gives [Ru₃H(CO)₈(PPh₃)(B₂H₅)] in good yield. Its molecular structure has been determined and the results confirm that it is a nido cluster related to pentaborane(9). Photolysis of [Ru₃H(CO)₉(B₂H₅)] with an excess of PPh₃ and time > 4 h yields mono-, bis- and tris-(triphenylphosphine)-substituted [Ru₃(CO)₉(BH₅)]via borane abstraction. The molecular structure of [Ru₃(CO)₆(PPh₃)₃BH₅]·CH₂Cl₂ has been determined, confirming the presence of a tetrahedral Ru₃B core. In solution, the isomer preferences for members of the series [Ru₃(CO)_9–x(PPh₃)_xBH₅](x= 1–3) have been studied and it is observed that the distribution of endo-hydrogen atoms in [Ru₃(CO)_9–x(PPh₃)_xBH₅](x= 0–3) depends on x.