Halocarbonyltungsten(II) Complexes Containing Tripodal Tris(pyrazolyl)borate Ligands

Abstract

The halo tricarbonyl complexes LWX(CO)3 (X = I, Br, Cl) are formed when NEt4[LW(CO)3] is reacted with I2, N-bromosuccinimide, and N-chlorosuccinimide (or PhICl2), respectively, while reaction of NEt4[LprW(CO)3] and I2 yields LPrWI(CO)3 [L = hydrotris(3,5-dimethylpyrazol-l-yl)borate, LPr = hydrotris(3-isopropylpyrazol-l-yl)-borate]. Reaction of NEt4[LW(CO)3] with Br2 yields mixtures of LWBr(CO)3 and LBrWBr(CO)3 [LBr = hydrotris-(4-bromo-3,5-dimethylpyrazol-l-yl)borate] as a result of competitive bromination of both tungsten and ligand L. The complexes generally exhibit three ν(CO) bands, one at ca. 2025 cm-1 and two between 1930 and 1900 cm-1, and NMR spectra consistent with fluxional carbony..