Trinuclear angular aggregates of rhodium: synthesis and crystal structures of [Rh3(µ3-SC5H4N)2(CO)6][ClO4](SC5H4N = pyridine-2-thiolate) and [Rh3(µ3-C7H4NS2)2(CO)2(PPh3)2(tfbb)][ClO4](C7H4NS2= benzothiazole-2-thiolate, tfbb = tetrafluorobenzobarrelene)

Abstract

The binuclear complexes [{Rh(µ-L)L′₂}₂]{L = pyridine-2-thiolate (SC₅H₄N^–) or benzothiazole-2-thiolate (C₇H₄NS₂^–); L′₂= cyclo-octa-1,5-diene (cod), norborna-2,5-diene (nbd), tetrafluorobenzobarrelene (tetrafluorobenzo[5,6]bicyclo[2.2.2]octa-2,5,7-triene, tfbb), (CO)₂, or (CO)(PPh₃)} react with the appropriate species cis-[RhL′₂(Me₂CO)_x]⁺ to give trinuclear aggregates [Rh₃(µ₃-L)₂(L′₂)₃][ClO₄]. A study of this reaction has led to the controlled synthesis of a single isomer of the complexes [Rh₃(µ₃-C₇H₄NS₂)₂(CO)₂(PPh₃)₂L′₂][ClO₄]. The trinuclear complexes have been characterized by ¹H, ³¹P n.m.r., and u.v.-visible spectroscopy and in the case of [Rh₃(µ₃-SC₅H₄N)₂(CO)₆][ClO₄]·0.5CH₂Cl₂(4) and [Rh₃(µ₃-C₇H₄NS₂)₂(CO)₂(PPh₃)₂(tfbb)][ClO₄](12) by single-crystal X-ray diffraction methods. In both structures trinuclear cationic rhodium complexes are present, in which two pyridine-2-thiolate[(4)] or benzothiazole-2-thiolate[(12)] ligands, acting as triple bridges through the nitrogen and one sulphur atom, interact with all three metal atoms, which are in a bent arrangement. Carbonyl ligands [(4)] and carbonyl, PPh₃, and tfbb (through the two double bonds) ligands [(12)] complete the slightly distorted square-planar co-ordination of the Rh atoms.