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) 2 Fe 2 (CO) 6 yielded a known complex [( μ -SCH 2 ) 2 CHC 6 H 5 ]Fe 2 (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 Me 3 NO·2H 2 O gave two chelate complexes [( μ -SCH 2 ) 2 CHC 6 H 5 ]Fe 2 (CO) 4 ( κ 2 -dppv), [A( κ 2 -dppv)] and [( μ -SCH 2 ) 2 CHC 6 H 5 ]Fe 2 (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 HBF 4 ·Et 2 O in dichloromethane at room temperature gave the bridging hydrides [( μ -H)A( κ 2 -dppv)]BF 4 and [( μ -H)A( κ 2 -dppe)]BF 4 . The complexes [( μ -H)A( κ 2 -dppv)]BF 4 , [A( κ 2 -dppe)] and [( μ -H)A( κ 2 -dppe)]BF 4 were characterized by elemental analysis and spectroscopic methods, and [( μ -H)A( κ 2 -dppv)]BF 4 and [( μ -H)A( κ 2 -dppe)]BF 4 were also characterized by X-ray crystallography. The electrochemical behavior of [( μ -H)A( κ 2 -dppv)]BF 4 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.