Reaction of polynuclear acetylide clusters. Synthesis of pentanuclear heterometallic clusters by addition of [M(CO)3(CCPh)(-C5H5)] to [MOs3(CO)11(CCPh)(-C5H5)](M = Mo or W). Crystal structures of [Mo2Os3(CO)11(CCPhCCPh)(-C5H5)2]?2H2O and [MoWOs3(CO)8(?4-C)-(?3-CPh)(CCPh)(-C5H5)2]?CH2Cl2