Base‐Initiated Formation of FeI–PNP Pincer Complexes

Abstract

Fe(I) PNP pincer complexes of the type [Fe(PNPNH)(CO)2]+ were prepared by treatment of the Fe(II) complexes [Fe(PNPNH)(CO)(Cl)2] with KOtBu in an aprotic solvent. The outcome of these reactions is independent of whether it is carried out under a CO atmosphere or not. The tert‐butyl analog [Fe(PNPNH‐tBu)(CO)2]Cl was obtained in a similar fashion but with [Fe(PNPNH‐tBu)(Cl)2] as starting material in the presence of CO. In all these reactions the formation of free PNP ligand together with unknown Fe(III) species is presumably due to a 2FeII → FeI and FeIII disproportionation process. The cationic complexes could be deprotonated upon treatment with KOtBu affording the neutral complexes [Fe(PNPN)(CO)2]. All compounds are low‐spin complexes as established by their solution effective magnetic moments, X‐band EPR spectra as well as DFT calculations. The solid‐state structures of two representative cationic and neutral complexes, respectively, were determined by single‐crystal X‐ray diffraction.