TRANSITION-METAL COMPLEXES WITH SULFUR LIGANDS .96. HYDROGENASE MODEL REACTIONS - D2/H+ EXCHANGE AT METAL SULFUR CENTERS CATALYZED BY [RH(H)(CO)(S-BU(4))] (S-BU(4)2- = 1,2-BIS((2-MERCAPTO-3,5-DI-TERT-BUTYLPHENYL)THIO)ETHANATO(2-))

In search of model complexes of hydrogenases, oxidative addition of the tetradentate thioether thiols '(bu)S4'-H-2 ('(bu)S4'-H-2 = 1,2-bis((2-mercapto-3,5-di-tert-butylphenyl)thio)ethane) and 'S4'-H-2 ('S4'-H-2 = 1,2-bis((2-mercaptophenyl)thio)ethane) to [RhI(Cl)(CO)2]2 gave [RhIII(H)(CO)('X4')] ('X4'2- = '(bu)S4'2- (1), 'S4'2- (3)). 1 exchanges its hydrido ligand for deuterium when reacted with either D+ ions or D2 in the presence of H+. Mechanisms of these reactions are suggested which include heterolytic cleavage of D2 and nonclassical dihydrogen complexes. The reaction with D2 implies a D2/H+ exchange which is one of the characteristic hydrogenase reactions. This D2/H+ exchange was further corroborated by the deuteration of EtOH by D2 to give EtOD in the presence of 1 as catalyst. Reactions of other rhodium(I) complexes such as [Rh(Cl)(cod)]2 and [Rh(Cl)(C2H4)2]2 with '(bu)S4'-H-2 yielded [(mu-'(bu)S4'){Rh(cod)}2] (4) and [Rh(Cl)('(bu)S4')]2 (5). When reacted with [Rh(Cl)(cod)]2, pentadentate '(bu)S5'-H-2 ('(bu)S5'-H-2 = bis(2-((2-mercapto-3,5-di-tert-butylphenyl)thio)ethyl)sulfide) formed meso-[Rh(Cl)('(bu)S5')] (meso-6) in addition to a mixture of diastereomers.