Molecular structure of W(PMe3)3H6 in the solid state and in solution

Abstract

The molecular structure of W(PMe3)3H6 has been identified by low temperature (−123°C) X-ray diffraction studies as a classical hydride compound, with a tricapped trigonal prismatic geometry in which two of the PMe3 ligands adopt eclipsed positions on opposite triangular faces of the prism and one PMe3 ligand caps a rectangular face. The solid state structure is reproduced well by density functional theory geometry optimization calculations on the molecule in the gas phase. NMR spectroscopic studies provide evidence that W(PMe3)3H6 also exists as a classical hydride compound in solution. For example, the T1(min) value for the hydride ligands of W(PMe3)3H6 is 380ms at 500MHz and 310ms at 400MHz, values that are more in accord with a classical hydride formulation than a nonclassical one. Likewise, the W(PMe3)3H6−xDx isotopologues (obtained by isotope exchange with either deuterobenzene or deuterotoluene) exhibit upfield (+13ppb) deuterium secondary isotope effects on the hydride chemical shift, which are also consistent with a classical description.