Synthesis of bridging hydrides of phenyl-functionalized diiron propanedithiolate complexes with 1,2-bis(diphenylphosphine)ethylene or 1,2-bis(diphenylphosphine)ethane ligands

Reaction of 2-phenyl-1,3-dibromopropane with in situ generated (μ-SLi)2Fe2(CO)6 yielded a known complex [(μ-SCH2)2CHC6H5]Fe2(CO)6 (A). Displacement of two carbonyls from complex A by cis-1,2-bis(diphenylphosphine)ethylene (dppv) or 1,2-bis(diphenylphosphine)ethane (dppe) in the presence of Me3NO·2H2O gave two chelate complexes [(μ-SCH2)2CHC6H5]Fe2(CO)4(κ 2-dppv), [A(κ 2-dppv)] and [(μ-SCH2)2CHC6H5]Fe2(CO)4(κ 2-dppe), [A(κ 2-dppe)], respectively. Protonation of the diiron centers of [A(κ 2-dppv)] and [A(κ 2-dppe)] using an excess of HBF4·Et2O in dichloromethane at room temperature gave the bridging hydrides [(μ-H)A(κ 2-dppv)]BF4 and [(μ-H)A(κ 2-dppe)]BF4. The complexes [(μ-H)A(κ 2-dppv)]BF4, [A(κ 2-dppe)] and [(μ-H)A(κ 2-dppe)]BF4 were characterized by elemental analysis and spectroscopic methods, and [(μ-H)A(κ 2-dppv)]BF4 and [(μ-H)A(κ 2-dppe)]BF4 were also characterized by X-ray crystallography. The electrochemical behavior of [(μ-H)A(κ 2-dppv)]BF4 was investigated by cyclic voltammetry, and the catalytic electrochemical reduction in protons from trifluoroacetic acid or p-methylbenzene sulfonic acid to give hydrogen was investigated.