Département de chimie moléculaire

The chem. of Fe2(μ-SH)2(CO)4(PPh3)2 (2HH) is described with attention to S-S coupling reactions. Produced by the reduction of Fe2(μ-S2)(CO)4(PPh3)2 (2), 2HH is an analog of Fe2(μ-SH)2(CO)6 (1HH), which exhibits well-behaved S-centered redox. Both 2HH and the related 2MeH exist as isomers that differ with respect to the stereochem. of the μ-SR ligands (R = H, Me). Compounds 2HH, 2MeH, and 2 protonate to give rare examples of Fe-SH and Fe-S2 hydrides. Salts of [H2]+, [H2HH]+, and [H2MeH]+ were characterized crystallog. Complex 2HH reduces O2, H2O2, (PhCO2)2, and Ph2N2, giving 2. Related reactions involving 1HH gave uncharacterizable polymers. The differing behaviors of 2HH and 1HH reflect stabilization of the ferrous intermediates by the PPh3 ligands. When independently generated by the reaction of 2HH with 2,2,6,6-tetramethyl-1-piperidinyloxy, 2* quant. converts to 2 or, in the presence of C2H4, is trapped as the ethanedithiolate Fe2(μ-S2C2H4)(CO)4(PPh3)2. Evidence is presented that the Hieber-Gruber synthesis of 1 involves polysulfido intermediates [Fe2(μ-Sn)2(CO)6]2- (n {\textgreater} 1). Two relevant experiments are as follows: (i) protonation of [Fe4(μ-S)2(μ-S2)(CO)12]2- gives 1 and 1HH, and (ii) oxidation of 1HH by S gives 1.