A Novel [FeFe] Hydrogenase Model with a (SCH₂)₂PO Moiety

A novel [FeFe]-hydrogenase model complex containing phosphine oxide in the dithiolato ligand, namely [Fe₂(CO)₆]­[(μ-SCH₂)₂(Ph)­PO] (<b>1</b>), has been synthesized and characterized. Complex <b>1</b> was prepared via the reaction of equimolar quantities of (μ-LiS)₂Fe₂(CO)₆ and OP­(Ph)­(CH₂Cl)₂. The protonation properties of complex <b>1</b> have been investigated by monitoring the changes in IR (in the ν­(CO) region) and ³¹P­{¹H} NMR spectra upon addition of pyridinium tetrafluoroborate, [HPy]­[BF₄], and HBF₄·Et₂O, suggesting protonation of the PO functionality. In addition, high-level DFT calculations on the protonation sites of complex <b>1</b> in CH₂Cl₂ have been performed and support our experimental observations that the PO unit is protonated by HBF₄·Et₂O. Cyclic voltammetric experiments on complex <b>1</b> showed an anodic shift of the oxidation peak upon addition of HBF₄·Et₂O, suggesting a CE process