Synthesis, crystal structure and protonation of the asymmetric iron-only hydrogenase model [Fe2(CO)3(μ-pdt){μ,η2-Ph2PCH2CH2P(Ph)CH2CH2PPh2}] (pdt = SCH2CH2CH2S)

Thermolysis of [Fe2(CO)6(μ-pdt)] with bis(2-diphenylphosphinoethyl)phenylphosphine (triphos) affords [Fe2(CO)3(μ-pdt){μ,η2-Ph2PCH2CH2P(Ph)CH2CH2PPh2}], the major form of which exists as an interconverting mixture of four isomers at room temperature. Protonation gives a bridging hydride complex in which the fluxionality appears to have been suppressed.