Synthesis of pentanuclear clusters derived from [Ru3RhH2(CO)10(PPh3)(µ-COMe)]. Crystal structures of [Ru3Rh2H2(CO)12(PPh3)2] and [Ru3RhAuH(CO)10(PPh3)2-(µ3-COMe)]

Abstract

Reaction of [Ru₃RhH₂(CO)₁₀(PPh₃)(η-COMe)]2 with K[BHBu^s₃] and then [Rh(CO)₃(PPh₃)₂][PF₆] afforded [Ru₃Rh₂H₂(CO)₁₂(PPh₃)₂]3 in 29% yield. A single-crystal X-ray diffraction characterisation of compound 3 was carried out: monoclinic, space group C2/c(no. 15), a= 19.409(4), b= 9.944(6), c= 26.153(4)Å, β= 103.35(2)°, Z= 4 and R= 0.033. A trigonal-bipyramidal cluster framework of C₂ symmetry was established, with an equatorial Ru₃ plane, and apical Rh(CO)(PPh₃) units. The hydride ligands cap two triangular faces. Using [Au(PPh₃)Cl] as an alternative electrophile, [Ru₃RhAuH(CO)₁₀(PPh₃)₂(µ₃-COMe)]4 and [Ru₃RhAuH₂(CO)₁₁(PPh₃)₂]5 were formed in 5 and 19% yields, respectively. Complex 4 was characterised by X-ray diffraction: triclinic, space group P(no. 2), a= 11.361(3), b= 13.745(4), c= 17.124(3)Å, α= 74.15(2), β= 74.59(2), γ= 73.02(2)°, Z= 2 and R= 0.037. This cluster also showed a trigonal-bipyramidal framework, with an equatorial Ru₂Rh plane and capping AuPPh₃ and Ru(CO)₂ units. There are three bridging ligands: the COMe ligand bridges the Ru₃ face, one CO bridges a Rh–Ru(apical) bond, and the hydride a Ru₂Rh face. Both these clusters are 72-electron species.