Carbon-sulfur bond activation by hydrido-bridged metal dimers and the synthesis, structure, and solution behavior of sulfur-bridged d8 metal dimers

Both the catalytic hydrodesulfurization of dibenzothiophene with [Ni (dippe)(mu-H)]2 and the removal of sulfur from [Ni (dippe)(mu-S)] 2 at various temperatures, H2 pressures, sulfur scavengers, and periods of time were unsuccessful. Yet, sulfur was successfully extracted from [Ni(dippe)(mu-S)]2 in a metathesis reaction with ZnEt 2 to form ZnS, [Ni(dippe)(eta2-C2H 4)], and ethane. While the [Ni(dippe)(mu-H)]2 system is noncatalytic, its palladium and platinum analogs were investigated. In regard to nickel-, palladium-, and platinum-thiophene metallocycle products, evidence for bond delocalization exists only for [Pt(dippe)(eta2-SC 4H4)].;The rhodium dimers [Rh(dippe)(mu-H)]2 and [Rh2(dippe) 2(mu-Cl)(mu-H)] react with dibenzothiophenes and phenoxythiin to form C-S bond cleavage products that contain a bridging thiolato group. Moreover, the former hydride ring-walks the biphenyl or diphenylether substituent of these thiolato-bridged products before it cleaves the remaining C-S bond to make free biphenyl or diphenyl ether.;The dimer [Ni(dippe)(mu-S)]2 reacts with organic electrophiles to give the alkylated species [Ni2(dippe)2(mu-S)(mu-SR)] +. Stronger alkylating agents lead to double alkylation and cleavage of the dimer, while protonation occurs in a similar manner with strong acids. Like [Ni2(dippe)2(mu-S)(mu-SR)]+, all [Rh(dippe)(mu-SR)]2 complexes except [Rh(dippe)(mu-SC 6H5)]2 exhibit bent geometry. 1H and 31P NMR spectroscopies indicate that both ring inversion and sulfur inversion exist among the members of this series, which allows them to access several isomeric forms when they are in solution.;[Ir(COD)(mu-Cl)]2 reacts with two equivalents of dippe to produce [Ir(dippe)(mu-Cl]2 at yields that are dependent upon the solvent. Its hinge angle theta is larger than other reported iridium analogs, but smaller than [Rh(dippe)(mu-Cl)]2. [Ir(dippe) 2][Ir(dippe)Cl2], whose anion is without literature precedent, is an intermediate species in the conversion of [Ir(dippe)(mu-Cl)] 2 to [Ir(dippe)2]Cl. Lastly, [Ir(dippe)2]Cl reacts with H2 to form [Ir(dippe)2H2]Cl.