SPECTROPHOTOMETRIC STUDIES ON COMPLEX-FORMATION IN DILUTE BENZENE SOLUTIONS OF [(RH(DIENE)(MU-CL))(2)]-PR3-SNCL3 SYSTEMS

There is no correlation between the stability of complexes formed in d ilute solutions of [{Rh(diene)(mu-Cl)}(2)]-PR3-SnCl2 systems [with lig and combinations cod + PPh3, nbd + PPh3, cod + PPhMe2 and cod + PCy3 ( Cy = cyclohexyl)] and the possibility of isolating them as solids. In general, high dilution favours the formation of pentacoordinate comple xes that decompose upon attempted crystallization [RhCl(cod)(PPhMe2)(2 )], [Rh(SnCl3)(cod)(PPh3)(2)], [Rh(SnCl3)(cod)(PCy3)(2)], [Rh(SnCl3)(c od)(PPhMe2)(2)] and [Rh(SnCl3)(nbd)(PPh3)(2)] have been identified in solution, but only the last two, previously known, have been isolated in the solid state. The steric properties of the coordinated phosphine seem to be the most important factor In determining the stabilities o f [RhCl(diene)(PR3)(2)] complexes, whilst in the case of [Rh(SnCl3)(di ene)(PR3)(2)] complexes the steric properties of the phosphine and the diene appear to have similar importance.