Spectroscopy of Phosphine Complexes. The Mössbauer signal for 2 (δ = 0.21 mm/s and |ΔEQ| = 1.25 mm/s, Figure ) is similar to those for 3-Na (δ = 0.24 mm/s and |ΔEQ| = 0.94 mm/s, Figure ) and 3-K (δ = 0.25 mm/s and |ΔEQ| = 1.05 mm/s, Figure ), consistent with low-spin iron(II) complexes. Solid 4 has a lower isomer shift of 0.16 mm/s and much larger quadrupole splitting of 3.45 mm/s, and its doublets are highly asymmetric, with ΓL = 0.57 mm/s, ΓR = 0.32 mm/s. To determine the spin state of 4, solid state and C6D6 solution magnetic moments were obtained. Both measurements gave µeff = 1.6 µB at 298 K, which indicates a ground-state spin of