Synthesis of triruthenium–rhodium tetranuclear clusters derived from [Ru3H3(CO)9(µ3-COMe)]. Crystal structure of [N(PPh3)2][Ru3RhH2(CO)11(PPh3)]·0.6C5H12

Abstract

Reaction of K[Ru₃H₂(CO)₉(µ₃-COMe)] with [Rh(CO)₃(PPh₃)₂](PPh₃)₂][PF₆] affords [Ru₃H₂(CO)₉(µ₃-COMe){Rh(CO)₂(PPh₃)}]3 in 80% yield, with [Ru₃H(CO)₉(PPh₃)(µ-COMe)], [Ru₃H(CO)₈(PPh₃)₂(µ-COMe)] and [Ru₃RhH₂(CO)₈(PPh₃)₃(µ-COMe)] as minor products; [Ru₃RhH₂(CO)₉(PPh₃)₂(µ-COMe)]8 was isolated from the corresponding reaction with [Rh(CO)(PPh₃)₂Cl] and exists as five interconverting isomers in solution. At room temperature 3 loses one CO group to form the tetrahedral cluster [Ru₃RhH₂(CO)₁₀(PPh₃)(µ-COMe)]7. This consists of two isomers in solution, with the major one being the molecular structure observed in the crystal. On reaction with K[BHBu^s₃], complex 7 undergoes a demethylation reaction to form [N(PPh₃)₂][Ru₃RhH₂(CO)₁₁(PPh₃)]9. A single-crystal X-ray diffraction study of [N(PPh₃)₂][Ru₃RhH₂(CO)₁₁(PPh₃)]·0.6C₅H₁₂ was carried out: triclinic, space group P1 (no. 1), a= 12.244(2), b= 13.453(3), c= 11.926(3)Å, α= 111.40(2), β= 101.30(2), γ= 70.02(1)°, Z= 1, R= 0.053 from 4349 observations [F > 3σ(F)]. This showed a structure derived from [Rh₄(CO)₁₂], with an apical Ru(CO)₂(PPh₃) unit, and the Rh atom in the basal plane. The two hydrides were not located directly, but are considered to bridge apical–basal Ru–Ru edges.