Tungsten(VI) complexes as new products in the high-intensity photolysis of octacyanotungstate(V) ion in hydroxylic solvents; crystal structure of [PPh4]2[W(CN)6O]·H2O and [PPh4]2[W(CN)5O(OMe)]

Abstract

Irradiation of octacyanotungstate(V) ion under high light intensities leads to new photoproducts based on W^VI not found at normal intensities. In water, the [W(CN)₆O]^2– ion is formed while in water–methanol (1:1 v/v) the [W(CN)₅O(OMe)]^2– ion is produced on standing after photolysis. The formation of these unexpected products is viewed as proceeding via a two-quantum process. The ions, in the form of their [PPh₄]₊ salts [(1) and (2) respectively], were structurally characterized by X-ray diiffraction as pentagonal bipyramids with five equatorial cyanide ligands. For (1), R= 0.028 for 6 786 unique observed [I/σ;(I) 3.0] reflections, and for (2), R= 0.051 for 6 865 unique observed [I/σ(I) 2.0] reflections. For both compounds, WO is 1.693(2)(mean), W–C (equatorial) is 2.167(24), W–C (axial) is 2.277(3), and W–O(Me)(axial) is 1.906(9)Å.