Mixed-metal carbido carbonyl clusters. Part 4. Synthesis and structural characterization of [Rh6C(CO)13{Au2(PPh3)2}]

Abstract

The new mixed-metal carbido-carbonyl cluster species [Rh₆C(CO)₁₃{Au₂(PPh₃)₂}] has been obtained by reaction of [Rh₆C(CO)₁₃]^2– with [Au(PPh₃)Cl]. The molecular structure has been determined by single-crystal X-ray diffractometry: orthorhombic, space group Fdd2, a= 22.335(4), b= 31.710(6), c= 14.947(7)Å, Z= 8, R= 0.045, and R′= 0.047. The cluster is a distorted Rh₆ octahedron with two adjacent triangular faces capped by Au(PPh₃) moieties which also establish an Au–Au bond; the CO-ligand stereogeometry is related to that of the parent dianion. The ³¹P and ¹³C solution n.m.r. spectra are consistent with a fluxional behaviour of both the CO groups and the two Au(PPh₃) moieties over the Rh₆ core. The compound reacts easily with CO (1 atm, 101 325 Pa; room temperature) yielding the bicapped trigonal prism [Rh₆C(CO)₁₅{Au(PPh₃)}₂].