Iron(II) complexes based on electron-rich, bulky PNN- and PNP-type ligands

Reaction of the PNN ligand ((2-(di-tert-butylphosphinomethyl)-6-diethylaminomethyl)pyridine) with 1 equiv. of anhydrous FeCl2 in THF results in the formation of (PNN)FeCl2 (1). The cationic complex [(PNN)Fe(THF)Cl](PF6) (2) was obtained by chloride abstraction from 1 with 1 equiv. of TlPF6. Similarly, the PNP-type complexes 3 and 4 were obtained from FeCl2 with 1 equiv. of t-Bu-PNP (2,6-bis(di-tert-butylphosphinomethyl)pyridine) and i-Pr-PNP (2,6-bis(di-iso-propylphosphinomethyl)pyridine), respectively. Complexes 1 and 3 were characterized by X-ray diffraction and elemental analyses. In both structures the Fe(II) centers exhibit a distorted square pyramidal geometry comprising two chloride ligands and one tridentate PNN or PNP ligand. The magnetic properties of the paramagnetic complexes 1–4 are discussed.