Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

Abstract

A bisphosphine in which a PhP–PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole ( 1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans- 1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO) 5(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC) 5M(μ- trans- 1)M(CO) 5 (M = W ( 2a), Mo ( 2b), Cr ( 2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans- 1 in the following way. Mono-nuclear complexes M( trans- 1)(CO) 5 (M = W ( 3a), Mo ( 3b), Cr ( 3c)) which had been prepared by a reaction of trans- 1 with one equivalent of the corresponding M(CO) 5(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans- 3a– c was converted to their respective cis isomer M( cis- 1)(CO) 5. Each cis trans mixture of the mono-nuclear complexes 3a– c was treated with the corresponding M(CO) 5(thf) to give a cis trans mixture of the respective dinuclear complexes 2a– c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W⋯W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans- 2a.