Transition metal eight-coordination. IV. Tetrakis(5,7-disubstituted-8-quinolinolato)tungsten(V) salts

Article abstract of DOI:10.1021/ic50113a020

Violet, paramagnetic [WQ₄]⁺ ions have been synthesized by a variety of methods and appear to be the first complexes of tungsten(V) possessing four chelate ligands. The 5,7-dichloro-8-quinolinol derivative has been synthesized by the reaction of either K₃W₂Cl₉ or W(CO)₆ with excess ligand at elevated temperatures for extended time periods or by treating the corresponding tungsten(IV) inner complex with Cl₂, Br₂, or HClO₄ at room temperature or with additional ligand at elevated temperatures. The 7-bromo-5-methyl-8-quinolinol-tungsten(V) species is rapidly produced in the melt reaction of the ligand with W(CO)₆. The [WQ₄]X salts, where X^- = Cl^-, Br^-, ClO₄^-, or Q^-, disproportionate in alcoholic or aqueous KOH to WQ₄ and tungsten(VI). Electronic transitions of the [WQ₄] species consist of several bands in the near-infrared and visible region in addition to the normal ligand spectral transitions. A magnetic moment of 1.7 BM, a 〈g〉 value of 1.872, and a ¹⁸³W hyperfine splitting of 85 G were observed for the dichloro derivative at room temperature. Low-temperature electron spin resonance spectra exhibit three anisotropic g values indicative of isomerization from the D_2d-mmmm isomer found for a related 5-bromo-8-quinolinol-tungsten(IV) chelate.^1a.