SYNTHESIS AND NMR-SPECTROSCOPY OF [T-BU2PHG(MU-PPH2)M(CO)(5)], M = CR, MO, W AND X-RAY STRUCTURE FOR M = CR, W

The title complexes (M = Cr (1), Mo (2) and W (3)) are prepared in alm ost quantitative yield from [t-Bu2PHgN(SiMe3)(2)] and [M(HPPh2)(CO)(5) ] or in 70% yield by synproportionation of [Hg(t-Bu2P)(2)] and [Hg{(mu -PPh2)M(CO)(5)}(2)]. The compounds are crystalline, air-stable in the solid state but oxygen-sensitive in solution. The solid state structur es of 1 and 3 consist of dimers containing four-membered (Hg-P)(2) rin gs with asymmetric phosphido bridges (252.2(2) pm and 268.9(2) pm for 1). The coordination geometry of Hg is almost planar. According to P-3 1 and Hg-199 NMR spectroscopy, the solution structure consists of dime rs at 173 K, whilst dissociation into monomers occurs at ambient tempe rature. (C) 1997 Elsevier Science S.A.