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 [Fe-2(CO)(6)][(mu-SCH2)(2)(Ph)P=O) (1), has been synthesized and characterized. Complex 1 was prepared via the reaction of equimolar quantities of (mu-LiS)(2)Fe-2(CO)(6) and O=P(Ph)(CH2Cl)(2). The protonation properties of complex 1 have been investigated by monitoring the changes in IR (in the nu(CO) region) and P-31{H-1} NMR spectra upon addition of pyridinium tetrafluoroborate, [HPy][BF4], and HBF4 center dot Et2O, suggesting protonation of the P=O functionality. In addition, high-level DFT calculations on the protonation sites of complex 1 in CH2Cl2 have been performed and support our experimental observations that the P=O unit is protonated by HBF4 center dot Et2O. Cyclic voltammetric experiments on complex 1 showed an anodic shift of the oxidation peak upon addition of HBF4 center dot Et2O, suggesting a CE process.