Susceptibility of the Tungsten-Tungsten Quadruple Bond to Oxidative Addition. Structure of an HCl Adduct

Article abstract of DOI:10.1021/ja00386a024

The complex W2<μ-H><μ-Cl>Cl222, 1, has been prepared from the reaction between 2 equiv of benzoic acid and 1 equiv of W2Cl44 and characterized by a single-crystal X-ray crystallographic study and NMR spectroscopy.Crystals of 1 belong to the space group P2₁2₁2₁ with a = 22.242(3) Angstroem, b = 25.516(3) Angstroem, c = 16.467(4) Angstroem, V = 9345(5) Angstroem³, and Z = 8.There are two crystallographically independent molecules per asymmetric unit, and the structure has been refined to R₁ = 0.043 and R₂ = 0.054.The structures of the two independent dinuclear molecules are essentially identical, each consisting of two distorted octahedra sharing an edge.There is a central W(O2CC6H5)2W unit that is planar except for the phenyl groups, and the hydrogen and chlorine atoms are placed above and below this plane forming a plane approximately perpendicular to the former.Terminal phosphine and chlorine ligands on each tungsten atom complete the distorted octahedra.The approximate symmetry is C_s, with the approximate plane of symmetry containing the bridging ligands.The tungsten-tungsten distances are 2.423(1) and 2.435(1) Angstroem, and the metal-metal bond is of formal order 3.This molecule provide the first structurally confirmed example of oxidative addition, in this case of HCl, to a tungsten-tungsten quadruply bonded dinuclear spacies.The bridging hydrogen atom was found in each molecule and its presence verified by 31P and 1H NMR spectra.The 1H resonance is at 1.92 ppm, and the couplings to phosphorus atoms are ²J_H-cisP = 31 Hz and ²J_H-transP = 63 Hz.