253432-87-0Relevant academic research and scientific papers
Reactions of H2, silanes, and olefins with superelectrophilic cationic rhenium complexes: Heterolytic cleavage of H2 and relation to the structure and function of hydrogenases
Huhmann-Vincent, Jean,Scott, Brian L.,Kubas, Gregory J.
, p. 240 - 254 (2008/10/08)
The reaction of cis-Re(CO)4(PR3)Me (R = Ph, Cy) with the Lewis acid B(C6F5)3 was studied by NMR spectroscopy, and was found to provide an equilibrium mixture of the solvent-coordinated complex [cis-Re(CO)4(PR3)(ClCH2Cl)][MeB(C 6F5)3] and the reactants. Reaction of [cis-Re(CO)4(PR3)Me with HX (X = H, SiEt3) in the presence of B(C6F5)3 at low temperature yielded the σ-bonded complexes [cis-Re(CO)4(PR3)(η2-HX)][MeB(C 6F5)3] which decomposed at room temperature via intramolecular heterolytic cleavage of the X-H bond to produce MeX and the hydride-bridged dimer [cis-Re(CO)4(PR3)]2(μ-H)]{MeB(C 6F5)3}. The unstable H2 binding and cleavage on this and other highly electrophilic organometallic complexes that contain strong π-acceptor CO ligands can be related to the structure and function of metalloenzymes such as Fe-containing hydrogenases that catalyze H2?2H+ + 2e-. The latter contain dinuclear organometallic-like active sites with CO ligands, which would promote binding and heterolytic cleavage of molecular H2 in biological systems. The Fe-Fe and Ni-Fe bonds in hydrogenases are likely sites for protonation to form a bridging hydride as the initial step in the mechanism of H2 formation, and electrophilic fragments such as [Re(CO)4(L)]+ strongly prefer to form bridging rather than terminal hydrides. The reaction of olefins and Et3SiH with the [cis-Re(CO)4(PR3)(ClCH2Cl)][BArF] (BArF = B[3,5-(CF3)2(C6H3)4 -]) system was also investigated, and the X-ray crystal structure of the dimer {[cis-Re(CO)4(PPh3)]2(μ-H)}{BArF} was determined.
