2 MONONUCLEAR TETRAPHENYLPHOSPHONIUM OXOCHROMIUM COMPLEXES - (PPH4)[CRVO3(H2O)] AND (PPH4)[CRVIO3(OH)]

The crystal structures of two isostructural compounds, tetraphenylphos phonium aquatrioxochromium(V), (1), [P(C6H5)4][CrO3(H2O)], and tetraph enylphosphonium hydroxytrioxochromium(VI), (2), [P(C6H5)4][CrO3(OH)], have been determined by single-crystal X-ray diffraction. (1) is param agnetic and (2) is diamagnetic. The P atoms in the cations of both str uctures lie on the crystallographic 4BAR symmetry axis at the unit-cel l origin. The anions are found near the 4BAR sites at 0, 1/2, 1/4 and are fourfold disordered. The Cr atoms in the anions have a deformed te trahedral coordination geometry with three normal Cr=O bonds [average 1.56 (3) angstrom] and a fourth Cr-O(aqua) or Cr-O(hydroxy) bond [2.07 (3) and 2.02 (3) angstrom in compounds (1) and (2), respectively].