Reactions of LW(S2PR2)(CO)2 (L = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with pyridine N-oxide produce carbonyl oxo complexes, LWIVO(S2PR2)(CO). Thermal decarbonylation of LWX(CO)2 (X = halide) complexes in organonitrile solvents produces 4-electron-donor nitrile complexes, LWIIX(η2-RCN)(CO), which react with NH4[S2PR2] to form LWII(S2PR2)(η2-RCN)(CO). Reactions of the nitrile complexes with propylene sulfide result in high yields of the carbonyl thio complexes LWIVSX(CO) or LWIVS(S2PR2)(CO). The structures of LWIVO(S2PPh2)(CO), (R)-LWII(S2PR*2)(η2-MeCN)(CO) (R* = (−)-mentholate), and LWIVS(S2PPh2)(CO) can be rationalized in terms of the π-bonding requirements of the electronically disparate π-acid and π-base ligands.

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The halo tricarbonyl complexes LWX(CO)(3) (X = I, Br, Cl) are formed when NEt(4)[LW(CO)(3)] is reacted with I(2), N-bromosuccinimide, and N-chlorosuccinimide (or PhICl(2)), respectively, while reaction of NEt(4)[L(Pr)W(CO)(3)] and I(2) yields L(Pr)WI(CO)(3) [L = hydrotris(3,5-dimethylpyrazol-1-yl)borate, L(Pr) = hydrotris(3-isopropylpyrazol-1-yl)borate]. Reaction of NEt(4)[LW(CO)(3)] with Br(2) yields mixtures of LWBr(CO)(3) and L(Br)WBr(CO)(3) [L(Br) = hydrotris(4-bromo-3,5-dimethylpyrazol-1-yl)borate] as a result of competitive bromination of both tungsten and ligand L. The complexes generally exhibit three nu(CO) bands, one at ca. 2025 cm(-)(1) and two between 1930 and 1900 cm(-)(1), and NMR spectra consistent with fluxional carbonyl-capped octahedral (C(s)()) structures. Crystals of L(Pr)WI(CO)(3).MeOH are orthorhombic, space group Pbca, with a = 11.779(2) Å, b = 15.975(4) Å, c = 29.476(3) Å, and V = 5547(2) Å(3) for Z = 8. The seven-coordinate complex exhibits a 3:3:1 carbonyl-capped octahedral structure. In hot acetonitrile or tetrahydrofuran, the tricarbonyl complexes are converted into brown, paramagnetic (&mgr;(eff) ca. 1.15 &mgr;(B)) dicarbonyl species, LWX(CO)(2) and L(Br)WBr(CO)(2), which exhibit two nu(CO) bands (ca. 1930 and 1840 cm(-)(1)) and isotropically shifted NMR spectra consistent with a mononuclear structure with C(s)() symmetry. Further decarbonylation of L(Br)WBr(CO)(2) in refluxing acetonitrile results in the formation of L(Br)WBr(MeCN-kappa(2)N,C)(CO), which crystallizes in monoclinic space group C2/c, with a = 22.245(4) Å, b = 19.077(4) Å, c = 15.639(3) Å, beta = 128.61(2) degrees, and V = 5286(2) Å(3) for Z = 8. The seven-coordinate complex features a "side-on" bonded, four-electron-donor acetonitrile ligand and a completely 4-brominated L(Br) ligand.

Reflux of LWX(CO) x (L = hydrotris(3,5-dimethylpyrazol-1-yl)borate; X = I, Br, Cl; x = 2, 3) and LPrWI(CO)3 (LPr = 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 LPrWI(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, OPr i , (−)-mentholate (R*), Ph). Microanalytical, mass spectrometric, and infrared, NMR (1H, 13C{1H}, 31P{1H}), 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-κ2 N,C ligand. For the nitrile ligand, the W−N1 and W−C2 bond distances are 2.033(6) and 2.051(7) Å, respectively, the N1−C2 bond distance of 1.225(9) Å is considerably longer than that for free acetonitrile (1.159(2) Å (gas phase)), and the ligand is bent with an N1−C2−C3 angle of 138.1(8)°. 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 π-orbital overlap. The structural and spectroscopic properties of the complexes are consistent with a four-electron-donor function for the nitrile ligands.