A New Tungsten Complex Derived from [(Diphenylphosphino)methyl]diphenylphosphine oxide.

Compounds containing phosphine and phosphinimide units provide bifunctionality from a "soft" phosphorus(III) center (which is predisposed for combination with soft metals) and a "hard" nitrogen center (which is predisposed for combination with early transition metals) so that the complex formation process is favored in a variety of situations. Ten years ago it was reported[1] that tungsten and molybdenum carbonyls react with N-trimethylsilyl[(diphenylphosphino)methyl] diphenylphosphinimide 1 to give the cyclometallophosphinimide phosphanes 2 and 3. In the course of our current research on the chemistry of [(diphenylphosphino)methyl]diphenyl phosphinimides we attempted a similar coordination of some N-aryl derivatives 4 under similar reaction conditions. In our hands, such small variation of the starting phosphinimides (N-aryl instead of N-trimethylsilyl) with respect to the scheme above resulted in notably different reaction products. Thus, the reaction of N-aryl[(diphenylphosphino)methyl]diphenylphosphinimides 4[2] with W(CO)5THF[3] gave rise to the previously unknown tungsten complexes 5 albeit in low yields. Compounds 5 precipitated out from the reaction medium as yellow solids and were isolated by filtration in virtually pure state.