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)Å, 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.