Hydrogenase biomimetics:structural and spectroscopic studies on diphosphine-substituted derivatives of Fe2(CO)6(µ-edt) (edt = ethanedithiolate) and Fe2(CO)6(µ-tdt) (tdt = 1,3-toluenedithiolate)

摘要

Reactions of a series of diphosphines with Fe2(CO)6(µ-edt) (1) and Fe2(CO)6(µ-tdt) (2) have been explored, the nature of the products being highly dependent upon the diphosphine. Reaction of 1 with bis(diphenylphosphino)methane (dppm) in acetonitrile at 82 °C affords monosubstituted Fe2(CO)5(κ1-dppm)(µ-edt) (3) in which the phosphine occupies an apical site and disubstituted Fe2(CO)4(µ-dppm)(µ-edt) (4) in which the phosphine is acting as a bridging ligand, while a similar reaction of 2 with dppm yields only Fe2(CO)4(µ-dppm)(µ-tdt) (5). In contrast, 1 and 2 react with 1,2-bis(diphenylphosphino)ethane (dppe) to form the chelate complex Fe2(CO)4(κ2-dppe)(µ-edt) (7) and Fe2(CO)4(κ2-dppe)(µ-tdt) (8), respectively; in both the diphosphine binds in an apical–basal fashion to a single iron atom. A second product of the dppe reaction with 1 is tetranuclear [Fe2(CO)5(µ-edt)]2(κ1,κ1-dppe) (6) in which the diphosphine again occupies apical sites. Similar reactions of 1 and 2 with 1,1′-bis(diphenylphosphino)ferrocene (dppf) give single products, namely Fe2(CO)5(κ1-dppf)(µ-edt) (9) and Fe2(CO)5(κ1-dppf)(µ-tdt) (10), respectively, which are structurally similar to 3. All seven complexes have been characterized by a combination of analytical and spectroscopic data, together with single-crystal X-ray diffraction analysis for 3, 7, 9 and 10.