Effects of spin change and unsaturation in the axial ligation of carbon monoxide and benzyl isocyanide to iron(II) macrocycles 14ane, 15ane, and TIM

Article abstract of DOI:10.1021/ic00133a068

Reversible coordination of carbon monoxide to low-spin Fe(14ane)(CH₃CN)₂²⁺ and high-spin Fe(15ane)(CH₃CN)₂²⁺ is reported. A 2000-fold increase in CO lability and P_1/2 for CO binding in the 15ane system is attributed to a synergistic combination of spin change and relief of macrocycle ring strain in the dissociation of CO. Benzyl isocyanide (BzNC) complexes of Fe(14ane) and Fe(TIM) are reported. Kinetic data for the reaction Fe(14ane)(CH₃CN)(BzNC)²⁺ + BzNC → Fe(14ane)(BzNC)(BzNC)²⁺ + CH₃CN are consistent with a dissociative mechanism involving a nondiscriminating reactive five-coordinate intermediate.