Reactions of hexakis(acetonitrile)iron(II) hexafluorophosphate in acetonitrile. Ligation of ammonia, pyridine, and trimethylamine to iron(II) and the behaviour of trimethyl phosphite and trimethylphosphine towards iron(II), nitrogen donor ligand complex cations

Co-ordinated acetonitrile in the hexakis(acetonitrile)iron(II) cation is replaced readily by ammonia or pyridine (py) at room temperature to give [FeL6]2+, L = NH3 or py. Only one trimethylamine ligand is co-ordinated to FeII under similar conditions. The cation [Fe(NH3)6]2+ exists as a discrete entity in MeCN, whereas [Fe(py)6]2+ looses py to give [Fe(py)6–x(NCMe)x]2+, x= 1 or 2. The cations react with trimethyl phosphite or trimethylphosphine in MeCN at room temperature to give low-spin FeII cations containing up to five ligated P(OMe)3 or three ligated PMe3 molecules. Both steric and electronic properties of the phosphorus ligands are important in determining the outcome of the reactions. The stereochemistry of the intermediate cations formed with P(OMe)3 depends on the identity of the N-donor ligands present.