Reactions of tetranuclear rhodium–triruthenium clusters with di- and tri-phosphines and with alkynes

Abstract

The compound [RhRu3(µ-H)2(µ-CO)(CO)9(cp)]1(cp =η5-C2H5) and an equimolar amount of diphosphine Ph2P(CH2)nPPh2[n= 1 (dppm), 2 (dppe) or 3 (dppp)] react at ambient temperature principally with cleavage of the heteronuclear cluster to form several homonuclear rhodium and ruthenium products. Isolated ruthenium clusters are simple phosphine derivatives of [Ru3(CO)12] or [Ru4(µ-H)4(CO)12], including [Ru3(µ-diphos)2(CO)8](diphos = dppm or dppe), [Ru3(µ-diphos)(CO)10] and [{Ru3(µ-diphos)(CO)9}2(µ-diphos)](diphos = dppe or dppp), and [Ru4(µ-H)4(CO)10(dppp)]. Reaction of 1 with the triphosphine MeC(CH2PPh2)3 affords hydrido-clusters [Ru3(µ-H)H(µ-triphos)(CO)8] and [Ru3(µ-H){µ-PPhCH2CMe(CH2PPh2)2(CO)8]12, the latter formed by elimination of benzene under very mild reaction conditions. The solid-state structure of cluster 12 has been determined by X-ray crystallographic analysis [monosolvate with dichloromethane, monoclinic, space group P21/n, a= 19.549(3), b= 14.2462(21), c= 16.429(4)A, β= 90.271(18)°, Z= 4, R= 0.051, R′= 0.060] and the geometrical non-rigidity of this asymmetric molecule in solution is revealed by variable-temperature 31P NMR spectroscopy. Reactions of cluster 1 with alkynes, RCCR (R = Ph or Et), give heteronuclear products, including isomers of [RhRu3(C2R2)(CO)9(cp)] and trimetallic clusters [RhRu2(C2R2)(CO)n(cp)](R = Et, n= 7; R = Ph, n= 8); from reaction of [RhRu3(µ-H)4(CO)9(η5-C5Me5)] with PhCCPh a related tetranuclear cluster [RhRu3(C2R2)(CO)9(η5-C5Me5)] is formed. A new, octahedral heteronuclear cluster [Rh2Ru4(µ-H)2(CO)12(cp)2] is also reported.