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Reaction of pentacarbonyl(eta(2)-bis(trimethylsilyl)ethyne)tungsten(0) with tricyclohexylphosphine: X-ray structure of pentacarbonyltricyclohexylphosphinetungsten(0)

2003-12-15
Demircan, O
Özkar, Saim
Ulku, D
Yildirim, LT
The pentacarbonyl(?(2)-bis(trimethylsilyl)ethyne)tungsten(0), W(CO)(5)(?(2)-btmse), reacts with tricyclohexylphosphine, PCy3, to yield two stable endproducts which could be isolated and fully characterized by using the single crystal X-ray diffractometry and the MS, IR, and NMR spectroscopy: W(CO)(5)(PCy3) and trans-W(CO)(4)(PCy3)(2). The former complex is the alkyne substitution product, while the latter one is formed from the conversion of its labile cis-isomer, which is generated by further reaction of the CO substitution product, cis-W(CO)(4)(?(2)-btmse)(PCy3), with a second PCy3 molecule. The intermediate cis-W(CO)(4)(?(2)-btmse)(PCy3) complex could not be detected even in the solution. The cis-W(CO)(4)(PCy3)(2) complex was observable, however, found to be instable and rapidly isomerizes to trans-W(CO)(4)(PCy3)(2). The crystal and molecular structure of W(CO)(5)(PCy3) was determined and compared with those of trans-W(CO)(4)(PCy3)(2). The coordination sphere around the W atom is a slightly distorted octahedron, involving five carbonyls and one phosphine. The W-C distances have values between 1.986(6) and 2.042(6) Angstrom. The W-P distance is 2.5794(12) Angstrom. Maximum deviation from an ideal octahedral coordination angle is observed to be 95.68(17)degrees. All three cyclohexyl rings are in chair configuration.