Four-electron-donor κ2N,C nitrile complexes of tungsten

Reflux of LWX(CO)(x) (L = hydrotris(3,5-dimethylpyrazol-1-yl)borate; X = I, Br, Cl; x = 2, 3) and (LWI)-W-Pr(CO)(3) (L-Pr = hydrotris(3-isopropylpyrazol-1-yl)borate) in organonitrile solvents produces LWX(RCN-N,C)(CO) (R = Me, Et, Ph for X = I; R = Me for X = Br, Cl) and (LWI)-W-Pr(MeCN-N,C)(CO), respectively. Reaction of LWI(MeCN)(CO) with NH4[S2PR2] in hot acetonitrile results in the formation of dithio ligand derivatives, LW(S2PR2-S)(MeCN-N,C)-(CO) (R = OEt, OPri, (-).mentholate (R*), Ph). Microanalytical, mass spectrometric, and infrared, NMR (H-1, C-13{H-1}, P-31{H-1}), and electronic spectroscopic data for the complexes are reported, along with the X-ray crystal structure of (R)-LW(S2PR*(2))(MeCN)(CO). The seven-coordinate complex contains a facially tridentate L ligand, carbonyl and monodentate dithiophosphate ligands, and a side-on-bonded acetonitrile-kappa(2)N,C ligand. For the nitrile ligand, the W-N1 and W-C2 bond distances are 2.033(6) and 2.051(7)Angstrom respectively, the N1-C2 bond distance of 1.225(9) Angstrom is considerably longer than that for free acetonitrile (1.159(2) Angstrom (gas phase)), and the ligand is bent with an N1-C2-C3 angle of 138.1(8)degrees. The non-hydrogen atoms of the W(MeCN)(CO) fragment are planar, and the nitrile methyl group is syn with respect to the metal carbonyl fragment; these features may be rationalized in terms of pi-orbital overlap. The structural and spectroscopic properties of the complexes are consistent with a four-electron-donor function for the nitrile ligands.