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

Heating Fe₂(CO)₆(μ-pdt)] (pdt = SCH₂CH₂CH₂S) and bis(2-diphenylphosphinoethyl) phenylphosphine (triphos) in toluene gives Fe₂(CO)₃(μ-pdt){μ,η²-Ph₂PCH₂CH₂P(Ph)CH₂CH₂PPh₂}], the major form of which has been characterised crystallographically. The complex is highly asymmetric; while one iron centre has the expected square-based pyramidal coordination environment, the second is nearer a trigonal bipyramid. In solution at room temperature, four isomers of the major form interconvert via two processes which can be frozen out at low temperature, while protonation affords a bridging hydride complex which appears to be static at all temperatures.