Solid-State Synthesis of Molybdenum and Tungsten Porphyrins and Aerial Oxidation of Coordinated Benzenethiolate to Benzenesulfonate

2012-06-04T00:00:00Z (GMT) by Goutam Nandi Sabyasachi Sarkar
A new route is developed for the synthesis of molybdenum and tungsten porphyrins using [M­(NO)<sub>2</sub>py<sub>2</sub>Cl<sub>2</sub>] (M = Mo, W) as the metal source and TPP (dianion of 5,10,15,20-<i>meso</i>-tetraphenylporphyrin) in the benzoic acid melt. Complexes [Mo<sup>V</sup>O­(TPP)­(OOCPh)] (<b>1</b>) and [W<sup>V</sup>O­(TPP)­(OOCPh)] (<b>2</b>) are isolated in almost quantitative yield. These are characterized by single-crystal X-ray structure analysis, electron paramagnetic resonance, electronic and IR spectroscopy, and magnetic moment measurements. Benzenethiol substitutes for PhCOO<sup>–</sup> in <b>1</b>, forming an intermediate thiolato complex that responds to the intramolecular redox reaction across the Mo<sup>V</sup>–SPh bond to yield [Mo<sup>IV</sup>O­(TPP)] (<b>3</b>). Under an excess of benzenethiol, PhS<sup>–</sup> is coordinated to the vacant site in <b>3</b>, which under aerial oxidation is oxidized to benzenesulfonate to form [Mo<sup>V</sup>O­(TPP)­(O<sub>3</sub>SPh)] (<b>4</b>). <b>2</b> undergoes similar aerial oxidation chemistry albeit slowly.