Synthesis and characterisation of fifteen-electron dihalo(carbonyl)tungsten(iii) complexes, Tp*WX2(CO) (X = Br, I)†
The oxidation of Tp*WIII(NCMe)(CO) [Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate] by iodine in refluxing acetonitrile produces paramagnetic Tp*WIIII2(CO), with μeff = 1.70 μB and ν(CO) = 1881 cm−1. The analogous bromo complex, Tp*WIIIBr2(CO) (μeff = 1.72 μB, ν(CO) = 1905 cm−1), is produced by the oxidative decarbonylation of Tp*WI(CO)3 with bromoacetonitrile in refluxing tetrahydrofuran. The crystal structures of both complexes reveal mononuclear, six-coordinate, distorted octahedral metal complexes bearing facial Tp* and mutually cis halide and carbonyl ligands. The structures, magnetic moments and spectroscopic data (including isotropically shifted NMR spectra) are consistent with a low-spin, doublet ground state in these, the first reported, 15-electron, d3 dihalo(carbonyl)–W(III) complexes.