New class of diiron dithiolates related to the Fe-only hydrogenase active site: synthesis and characterization of [Fe2(SR)(2)(CNMe)7]2+

Electron-rich polyisocyano derivatives Fe(2)(S(2)C(n)H(2n)(CO)(6-x)(CNMe)(x) (x approximately 4) undergo oxidatively induced (FeCp(2)(+)) reaction with additional CNMe to give Fe(2)(SR)(2)(CNMe)(7)](PF(6))(2), a new class of iron thiolates. Crystallographic characterization established that the 34 e(-) dinuclear core resembles the oxidized (H(2)-binding) form of the active sites of the Fe-only hydrogenases, key features being the face-sharing bioctahedral geometry, the mu-CX ligand, and an Fe-Fe separation of 2.61 A. Oxidation of the phenylthiolate Fe(2)(SPh)(2)(CO)(2)(CNMe)(4) led to mononuclear Fe(SPh)(CNMe)(5)](PF(6)), which is analogous to Fe(2)(SR)(2)(CNMe)(10)](PF(6))(2) formed upon treatment of Fe(2)(S(2)C(3)H(6))(CNMe)(7)](PF(6))(2) with excess CNMe.