Synthesis and Characterization of a Terminal Iron(II)-PH₂ Complex and a Series of Iron(II)-PH₃ Complexes

Reported is the reaction of a series of iron(II) bisphosphine complexes with PH₃ in the presence of NaBAr^F₄ [where BAr^F₄ = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate]. The iron(II) bisphosphine reagents bear two chlorides or a hydride and a chloride motif. We have isolated six different cationic terminal-bound PH₃ complexes and undertaken rigorous characterization by NMR spectroscopy, single crystal X-ray diffraction, and mass spectrometry, where the PH₃ often remains intact during the ionization process. Unusual bis- and tris-PH₃ complexes are among the compounds isolated. Changing the monophosphine from PH₃ to PMe₃ results in the formation of an unusual Fe₇ cluster, but with no PMe₃ being ligated. Finally, by using an iron(0) source, we have provided a rare example of a terminally bound iron-PH₂ complex.