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 (mu-SLi)(2)Fe-2(CO)(6) yielded a known complex [(mu-SCH2)(2)CHC6H5]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 Me3NO center dot 2H(2)O gave two chelate complexes [(mu-SCH2)(2)CHC6H5]Fe-2(CO)(4)(kappa (2)-dppv), [A(kappa (2)-dppv)] and [(mu-SCH2)(2)CHC6H5]Fe-2(CO)(4)(kappa (2)-dppe), [A(kappa (2)-dppe)], respectively. Protonation of the diiron centers of [A(kappa (2)-dppv)] and [A(kappa (2)-dppe)] using an excess of HBF4 center dot Et2O in dichloromethane at room temperature gave the bridging hydrides [(mu-H)A(kappa (2)-dppv)]BF4 and [(mu-H)A(kappa (2)-dppe)]BF4. The complexes [(mu-H)A(kappa (2)-dppv)]BF4, [A(kappa (2)-dppe)] and [(mu-H)A(kappa (2)-dppe)]BF4 were characterized by elemental analysis and spectroscopic methods, and [(mu-H)A(kappa (2)-dppv)]BF4 and [(mu-H)A(kappa (2)-dppe)]BF4 were also characterized by X-ray crystallography. The electrochemical behavior of [(mu-H)A(kappa (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.