Chemistry of cyclopentadienyl tricarbonylchromium dimer. Cleavage of bis(thiophosphoryl)disulfanes. Syntheses and X-ray crystal structures of CpCr(CO)2(S2P(OR)2), CpCr(S2P(OR)2)2 and Cr(S2P(OR)2)3 (R=iPr)

The facile reaction of [CpCr(CO)3]2 (Cp=η5-C5H5) with one mole equivalent of bis(thiophosphoryl)disulfanes, (RO)2P(S)SSP(S)(OR)2 (R=iPr), at ambient temperature, led to the isolation of dark-purple solids of CpCr(CO)2(S2P(OR)2) (2, yield: 32%) and blue solids of CpCr(S2P(OR)2)2 (3, yield: 30%). At 70–80 °C, the reaction gave 3 (yield: 35%) and Cr(S2P(OR)2)3 (4, yield: 11%). 1H-NMR spectral studies demonstrated that 3 and 4 were derived from 2, the primary product. X-ray diffraction analyses showed that 2 possesses cis CO ligands and a bidentate SP(S)(OR)2 ligand, while 3 contains both an unidentate and a bidentate ligand, and in 4 the Cr atom is octahedrally symmetrically coordinated to the three bidentate phosphorylthioato ligand. Variable temperature 1H and 31P spectral studies showed the occurrence of very rapid unidentate–bidentate exchange between the ligands in 3 in the temperature range −65 to 80 °C. It is also shown that the CrCr complex [CpCr(CO)2]2 reacted with [(iPrO)2P(S)S]2, albeit much less readily, generating 3 as the eventual product.