Regiospecific reaction between dimetallic phosphido-bridged W-W complexes and phosphane imide - Electrophilic site switching by metal-metal bond formation

Reaction between CPW(CO)(2)(mu-PPh2)W(CO)(5)(W-W) (2) and Ph(3)p=NR (R = Pr, CH2Ph, iPr) in THF at refluxing temperature is regiospecific with the CNR ligand coordinated to the W(CO)(4) unit to produce CpW(CO)(2)(mu-PPh2)W(CO)(4)- (CNR)(W-W) (4). Spectroscopic data indicate that the complex exists in two stereoisomeric forms in solution. The structure of the cis isomer was determined by a single-crystal Xray diffraction study which indicates that the CNR ligand is coordinated to the W atom of the W(CO)(4) unit and cis to the phosphido bridge. Reaction between CpW(CO)(3)(mu-PPh2)W(CO)(5) (1) and Ph3P=NR (R = Pr, CH2Ph, iPr) in THF under similar condition is also regiospecific. However, the CNR ligand is coordinated to the CpW site to produce CPW(CO)(2)(CNR)(mu-PPh2)W(CO)(5) (3). There are also two stereoisomers of the complex, which were separated by column chromatography. Structures of both isomers were determined by single-crystal X-ray diffraction studies. ((C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002).