Trinuclear aggregates of rhodium and iridium supported by thiolate bridges: synthesis and crystal structure

Abstract

A high-yield synthesis of the complexes [{M(µ-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(µ-SPh)(diolefin)}₂] affords the homotrinuclear aggregates [M₃(µ-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(µ₃-SPh)₂(diolefin)₂(diolefin′)]⁺, having different diolefins, and [M₂M′(µ₃-SPh)₂(diolefin)₃]⁺, containing different metal atoms and diolefins. In this way, homo- and heterotrinuclear complexes of the Rh₃³⁺, Ir₃³⁺, IrRh₂³⁺ and Ir₂Rh³⁺ cores have been isolated. Reaction of [M₃(µ₃-SPh)₂(diolefin)₃]⁺(M = Rh or Ir) with carbon monoxide leads to breakdown of the aggregates to give [{M(µ-SPh)(CO)₂}₂]. The new compounds have been characterized by analytical, spectroscopic (¹H NMR) and, particularly [Rh₃(µ₃-SPh)₂(cod)₃][ClO₄], by X-ray diffraction techniques. Crystals of the latter are orthorhombic, space group Pbca(no. 61), a= 14.818(1), b= 17.084(1), c= 27.443(1)Å, Z= 8, R= 0.0326 and R′= 0.0344 for 2908 unique reflections with F 6.0σ(F). The cation [Rh₃(µ₃SPh)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)Å.