Unexpected Rearrangement of 4-Chloro-2-butenylphosphinidene to 1-Chloro-2-vinylphosphirane in the Coordination Sphere of Tungsten

The complex (4-chloro-2-butenylphosphinidene)pentacarbonyltungsten, as generated from the appropriate 7-phosphanorbornadiene complex at 58 °C in the presence of copper(I) chloride as a catalyst, readily rearranges to give the stable 1-chloro-2-vinylphosphirane complex. According to DFT calculations on similar Cr(CO)5 complexes, a concerted six-electron (σ C−Cl bond, P lone pair, and π CC double bond), five-center mechanism could be involved with a low energy barrier of 4.8 kcal mol-1 in the chromium series.