Synthesis, spectroscopic and structural characterisation of chromium(0), molybdenum(0) and tungsten(0) complexes involving primary and secondary phosphines

[M(CO)(6)] (M = Mo or W) reacts with 4.5 molar equivalents of L (L = PPh2H or PPhH2) in excess ethanolic NaBH4 to yield the fac-trisubstituted species [M(CO)(3)(L)(3)] in good yield, with no evidence for species with lower degrees of substitution. IR, H-1-, C-13{H-1}-, P-31{H-1}- and Mo-95-NMR spectroscopy on these compounds, together with X-ray crystallographic studies on two examples, confirm the fac-tricarbonyl arrangement both in solution and in the solid state. Similar reactions involving PCy2H yield only the cis-disubstituted species [M(CO)(4)(PCy2H)(2)]. Reaction of [M'(CO)(4)(nbd)] (M' = Cr or Mo) or [W(CO)(4)(TMPA) (TMPA = tetramethylpropylenediamine) with two molar equivalents of L (L = PPh2H, PPhH2 or PCy2H) or with one molar equivalent of L-L (L-L = o-C6H4(PH2)(2), PhHPCH2CH2PHPh or PhHPCH2CH2CH2PHPh) in warm toluene solution give [M'(CO)(4)(L)(2)], [W(CO)(4)(L)(2)], [M'(CO)(4)(L-L)] or [W(CO)(4)(L-L)], respectively. Spectroscopic studies indicate that these all exist as cis-disubstituted species in solution and single-crystal X-ray analyses on three examples confirm this assignment in the solid state. The primary and secondary phosphines act as neutral two-electron donors in all cases with retention of the P-H functions. Trends in the spectroscopic and structural data are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.