Synthesis and properties of five-co-ordinate complexes of ruthenium and osmium containing the bulky phosphine 1,2-bis(diisopropylphosphino)ethane (dippe).: Crystal structure of [Ru(SPh)(dippe)2]-[BPh4]

The reaction of [RuCl2(dippe)(2)][dippe = 1, 2-bis(diisopropylphosphino)ethane] with NaBPh4 in MeOH afforded the red-brown five-co-ordinate complex-[RuCl(dippe)(2)][BPh4] 1. In analogous fashion, the complex cis-[OsCl2(dippe)(2)] 2, prepared by reaction of [NH4](2)[OsCl6] with dippe in refluxing 2-methoxyethanol, yielded the corresponding five-co-ordinate species [OsCl(dippe)(2)][BPh4] 3 upon treatment with NaBPh4 in MeOH. Both complexes 1 and 3 react with PhSH furnishing the five-co-ordinate benzenethiolato derivatives [Ru(SPh)(dippe)(2)][BPh4] 4 and [Os(SPh)(dippe)(2)][BPh4] 5 respectively. The crystal structure of 4 has been determined, and shows that the complex cation adopts a distorted trigonal-bipyramidal geometry. With the I exception of 4, which is rigid on the NMR time-scale, the other five-co ordinate complexes are stereochemically non-rigid, and in some instances undergo dynamic processes in solution which have been ascribed to interactions with the solvent. Whereas complexes 1 and 5 do not react with H-2, addition of H-2 to 3 yields the dihydrogen complex trans-[OsCl(H-2)(dippe)(2)][BPh4] 6. The reaction of 4 with H-2 afforded the known five-co-ordinate hydride complex [RuH(dippe)(2)][BPh4], formed presumably by elimination of HSPh from an unstable thiolate-dihydrogen (or dihydride) complex, namely [Ru(SPh)(H-2)(dippe)(2)][BPh4].