Synthesis of heteronuclear gold–rhodium cluster compounds and structural characterisation of [Rh(CNC8H9)3(AuPPh3)5]2+, [Rh(CNC8H9)2(AuPPh3)6(AuCl)2]+and [Rh(CO)2(AuPPh3)7]2+

Abstract

The NaBH4 reduction of a mixture of [Au(PPh3)Cl] and [Rh(CNC8H9)3Cl] leads to a dark red solution containing several Au–Rh cluster compounds, from which [Rh(CNC8H9)3(AuPPh3)5]2+1 and [Rh(CNC8H9)2(AuPPh3)6(AuCl)2]+2 have been isolated. The cluster [Rh(CO)2(AuPPh3)7]2+3 has been synthesised by addition of 1 equivalent of [Au(PPh3)(NO3)] to the tetrahydrofuran-soluble fraction of a solution obtained by the borohydride reduction of a mixture of [Au(PPh3)(NO3)] and [Rh(CO)2(MeCN)2]NO3. Compounds 1 and 3 have been characterised using 31P-{1H} NMR, IR and fast atom bombardment mass spectroscopy and single-crystal X-ray techniques. Since 2 was formed only in low yield it has been characterised only by single-crystal X-ray diffraction methods. The structures of the three compounds are related and may be described as derivatives of a rhodiumcentred Au12 icosahedron formed by removing four, five and seven vertices from the icosahedral cage.