UNUSUAL H-1-NMR PROPERTIES OF TUNGSTEN(II) TRIS(PYRAZOLYL)BORATE HYDRIDE COMPLEXES

Protonation of several [TpW(CO)3]- salts, substituted differently on the pyrazolyl rings, yields a series of [TpW(CO)3H] complexes. The hydride chemical shift lies in the normal range for such complexes (sigma -2 to -3 ppm), but the one-bond J(WH)-W-183 value is surprisingly low (5-9 Hz). A related alkyne derivative has been prepared by reaction of Na[BH4] with [Tp(I)W(CO)(PhC = CMe)][BF4] to give [Tp(I)W-(CO)(PhC = CMe)H] as the net result of H- for MeCN substitution. The hydride chemical shift is surprisingly far downfield in this complex (sigma-10.8 ppm), but the one-bond J(WH)-W-183 value is large (115 Hz). Single-crystal X-ray structures of [Tp(I)W(CO)3H] (monoclinic, space group P2(1)/c, a = 8.032 (1) angstrom, b = 13.978 (4) angstrom, c = 18.878 (5) angstrom, beta = 98.11 (2)-degrees, V = 2098 (2) angstrom 3, Z = 4, R = 0.039, R(w) = 0.037) and [Tp(I)W(CO)(PhC = CMe)H] (triclinic, space group P1BAR, a = 11.411 (7) angstrom, b = 12.311 (7) angstrom, c = 12.63 (1) angstrom, alpha = 74.31 (7)-degrees, beta = 64.05 (7)-degrees, gamma = 75.55 (5)-degrees, V = 1519 (2) angstrom 3, Z = 2, R = 0.058, R(w) = 0.064) are reported; the hydride ligands were not located, but the integrity of all the other ligands is reassuring evidence that these are indeed tungsten(II) hydride monomers.