TRINUCLEAR AGGREGATES OF RHODIUM AND IRIDIUM SUPPORTED BY THIOLATE BRIDGES - SYNTHESIS AND CRYSTAL-STRUCTURE

A high-yield synthesis of the complexes [{M(mu-SPh)(diolefin)}2][M = Rh or Ir; diolefin = cycloocta-1,5-diene (cod), norborna-1,4-diene (nbd), or tetrafluorobenzobarrelene (tfbb)] has been developed. Addition of the solvated species [M(diolefin)(Me2CO)x]+ to the binuclear complexes [{M(mu-SPh)(diolefin)}2] affords the homotrinuclear aggregates [M3(mu-3-SPh)2(diolefin)3]+ (M = Rh, diolefin = cod, nbd, or tfbb, M = Ir, diolefin = cod) in quantitative yield. This type of reaction can be used for the synthesis of the cations [M3(mu-3-SPh)2(diolefin)2(diolefin')]+, having different diolefins, and [M2M'(mu-3-SPh)2(diolefin)3]+, containing different metal atoms and diolefins. In this way, homo- and hetero-trinuclear complexes of the Rh3(3+) ,lr3(3+), IrRh2(3+) and Ir2Rh3+ cores have been isolated. Reaction of [M3(mu-3-SPh)2(diolefin)3]+ (M = Rh or Ir) with carbon monoxide leads to breakdown of the aggregates to give [{M (mu-SPh) (CO)2}2]. The new compounds have been characterized by analytical, spectroscopic (H-1 NMR) and, particularly [Rh3(mu-3-SPh)2(cod)3] [ClO4], by X-ray diffraction techniques. Crystals of the latter are orthorhombic, space group Pbca (no. 61), a = 14.818(l ), b = 17.084(l ), c = 27.443(1) angstrom, Z = 8, R = 0.0326 and R' = 0.0344 for 2908 unique reflections with F greater-than-or-equal-to 6.0-sigma(F). The cation [Rh3(mu-3-SPh)2(cod)3]+ shows a triangular arrangement of rhodium atoms capped on each side by triply bridging phenylthio groups. Each rhodium atom completes a square-planar co-ordination being bonded to a cod molecule. The metal atoms are separated by non-bonding distances, 2.9797(8), 3.3697(7) and 3.4937(8) angstrom.