Oxo-thiomolybdates

Oxo-thiomolybdates, [Mo04 S ] " n - 1-3), are prepared by the reaction of molybdate solutions with H2S under strictly controlled conditions of pH, temperature, and counterion. Excellent reviews of the syntheses and properties of these historically important four-coordinate tetrahedral species are available (174, 175). 

Binary Thiomolybdates and Tertiary Oxo/thiomolybdates A. The (MoS,04-,) Anions Binary Thiomolybdates Tertiary Oxo/thiomolybdates... 

For a variety of reasons (7) none of the [MoOS] " complexes described above constitute realistic enzyme models. The complexes in 2 and 3 do, however, demonstrate the feasibility of producing oxo-thio- and dithio-Mo(VI) complexes in addition to the simple thiomolybdates in 1. 

Deactivation of oxidized xanthine oxidase by cyanide produces thiocyanate and an inactive or desulfo form of the enzyme. The oxidized desulfo enzyme contains a dioxo-Mo(VI) center. Since it is generally believed that a terminal thio ligand on Mo is removed in the cyanolysis reaction, the interaction of oxo-thio-Mo(VI) complexes with CN is worthy of investigation. In general, reactions of thio-Mo( VI) complexes (typically thiomolybdates) with cyanide leads to the formation of SCN" by formal sulfur atom transfer and reduction of the metal, e.q., Eq. (25). 

So far, two synthetic methods for the preparation of the di- -sulfido cysteinato complex have been reported (1) bubbling H2S gas into the di-/i-oxo complex, [Mo204(cys)2] , in water, (2) reduction of a one-to-one (1 1) mixture of thiomolybdate and molybdate by sodium dithionite, followed by the addition of the ligand. ... 

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