Dithiolato- and Diselenolato-Bridged Nickel–Iron Biomimetics for the Active Site of [NiFe]Hydrogenases

As the active site models of [NiFe]­hydrogenases,
three types of
dichalcogenido E (E = S, Se)-bridged NiFe complexes (dppb)­Ni­[μ-E­(CH2)3E-μ]­Fe­(CO)3 (dppb = bis­(1,2-diphenylphosphino)­benzene, 2a, E = S; 2b, E = Se), {(dppb)­Ni­[μ-E­(CH2)3E-μ]­(μ-H)­Fe­(CO)3}­BF4 (3a, E = S; 3b, E = Se), and {(dppb)­Ni­[μ-E­(CH2)3E-μ]­(μ-D)­Fe­(CO)3}­BF4 (4a, E = S; 4b, E = Se) were prepared
by starting from the precursors (dppb)­Ni­[μ-E­(CH2)3E-μ] (1a, E = S; 1b, E = Se)
in satisfactory yields. While coordinations of 1a,b with Fe2(CO)9 gave the first-type
dichalcogenido-bridged models 2a,b, the
protonations of 2a,b with HBF4·Et2O afforded the second-type dichalcogenido-bridged μ-hydride models 3a,b the
oxidative additions of 2a,b with DCl followed
by anionic exchanges of the resulting intermediates with NaBF4 produced the third-type dichalcogenido-bridged μ-deuteride models 4a,b. Models 2a,b–4a,b were
all fully characterized by elemental analysis, spectroscopy, and X-ray
crystallography, and the H/D exchange reactions of μ-hydrides 3a,b with D2 and D2O were
further studied under light irradiation by 1H and 2H NMR spectroscopy.