Oligomerization of Terminal Phosphinidene Complexes

The thermolysis of a 7-phenyl-7-phosphanorbornadiene pentacarbonylchromium complex yields a mixture of the cyclic trimer and tetramer of [PhP-Cr(CO)5]. In the presence of CuCl and W(CO)6 at 60 °C, the decomposition of 7-R-7-phosphanorbornadiene pentacarbonyltungsten complexes affords the corresponding diphosphene σ,π complexes [RPPR][W(CO)5]3 (R = Me, CH2CH2CO2Et, 2-thienyl, 2-N-methylpyrrolyl). The Me derivative has been characterized as its [4+2] cycloadduct with 2,3-dimethylbutadiene. The three others have been characterized by X-ray crystal structure analysis, NMR, and UV, and the electronic structure of the thienyl derivative has been studied by DFT calculations.