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The binuclear, thiolate-bridged complexes [Et4N]2[M2(CO)8(SR)2] (M = Mo, W; R = Ph, t-Bu, Bz) (1), are prepared by refluxing M(CO)6 with [Et4N]SR in acetonitrile. On the basis of analytical, spectroscopic, and conductometric data, they are characterized as 2:1 electrolytes with the dinuclear dianions consisting of two metal(0)-(CO)4 fragments bridged by two µ-SR moieties. The complexes are converted to the corresponding M[2 dimers, M2(CO)8(SR)2 (2), by two-electron electrochemical oxidation (in a single step) (eq i) or treatment with a mild chemical oxidant, to the solvolyzed M*2 dimers, M2(CO)6(MeCN)2(SR)2 (3), byoxidation in acetonitrile, and to the monomeric M°s pecies, [M(CO)5(SR)]~(4) (for M = Mo, R = Ph, r-Bu), by treatment with excess CO. Interconversion of 1-4 by means of redox, solvolysis, and carbonylation reactions and the influence of the solvolysis and carbonylation reactions on electrode reactions (eq i) are described. Oxidation of the M°2 to the M[2 dimers is accompanied by formation of a single metal-metal bond and significant rearrangement within the M2(SR)2 core. These changes apparently supply the driving force that enables two-electron transfer to occur in a single step. Comparisons with structurally analogous compounds indicate that contractions of ~1.0 Á in the M-M bond distance and of ~25°in the M-S-M bridge angle accompany M°2 -*• M*2 oxidation. Despite these large displacements in nuclear coordinates, electrode reaction i exhibits Nernstian two-electron behavior by cyclic voltammetry at 0.1 V s'1. This kinetically facile behavior suggests that the nuclear rearrangement involved in conversion of [M2(CO)8(SR)2]2~t o M2(CO)8(SR)2 is concerted in such a way that a low activation energy barrier is presented to electron transfer.

The inhibition of the thermal reaction between hydrogen and oxygen by hydrogen bromide lias bccn studied over a wide range of mixture composition and vessel diameter at 50072 using vessels coated with boric acid. Under these conditions, surface reactions arc unimportant and the inhibition arises through the sequence of reactions : H+HBr = H24-Br

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