Abstract
Treatment of TaCl2(dmpe)2 (dmpe = l,2-bis(dimethylphosphino)ethane) with K[PPh2]-2dioxane affords a seven- coordinate, Ta(III) hydride, TaH(PPh2)2(dmpe)2. Crystals of the complex are triclinic, space group PI, with a = 10.556 (3) Á, b = 11.175 (3) Á, c = 18.663 (5) Á, a = 76.00 (3)°, ß = 74.48 (3)°, y = 66.60 (3)°. Full-matrix least-squares refinement
of positional and thermal parameters for all nonhydrogen atoms (including fixed contributions for phenyl H atoms) led to R
= 0.077 and R¡y = 0.093. The molecular structure of the complex consists of a well-defined pentagonal bipyramid, with apical,
monodentate PPh2 moieties, and two dmpe ligands plus a hydride ion in the pentagonal plane. The hydride ion was not refined, but its position was inferred from a peak on a final difference map, as well as from large P-Ta-P angle distortions in the pentagonal plane.