Treatment of cis-(Me3P)(4)FeMe2 with orthosubstituted diarylimines afforded 2 equiv of MeH, PMe3, and {mer-kappa C,N,C'-(Ar-2-yl)CH2N=CH(Ar'-2-yl))Fe(PMe3)(3) (Ar = 3,4,6-(F)(3)-C6H, Ar' = 3,5-(CF3)(2)-C6H2 1a; Ar = 3,4,6-(F)(3)C6H, Ar' = 3,4,5-(PF)(3)-C6H, 1b; Ar = 4,6,6-(F)(3)-C6H, Ar' = 3,5-(CP3)(2)-C6H2, 1c; Ar = C6H4, Ar' = 3-(OMe)-C6H3, id; Ar = 4,5,6-(F)(3)-C6H, Ar' = 3,6-Me-2-C6H3, 1e; Ar = C6H4, Ar' = 3,6-Me-2-C6H2, 10. Exposure of 1a f to O-2 caused rapid degradation, but substitution of the unique PMe3 with N-2 occurred when 1a-f were exposed to air or N-2 (1 atm), yielding (mer-kappa C,N,C'-(Ar-2-yl)CH2N=CH(Ar'-2-yl))Fe(PMe3)(2)L (L = N-2, 2a-f); CO, CNMe, and N2CPh2 derivatives (L = CO, 3a-d,f; L = CNMe, 8h; L = N2CH2, 9b) were prepared. Dihydrogen or NH3 binding to {mer-kappa C,N,C'-(3,4,6-(F)(3)-C6H-2-yl)CH2N=CH-(3,4,5-(F)(3)-C6H-2-yl)}Fe(PMe3)(2) (1b', S = 1 (calc)) to provide Sb (L = H-2) or 6b (L = NH3) was found comparable to that of N-2, while PMe3 (1b) and pyridine (L = py, 7h) adducts were unfavorable. Protolytic conditions were modeled using HCCR as weak acids, and trans-{kappa C,N-(3,4,5-(F)(3)-C6H2)CH2N= CH(3,4,6-(F)(3)-C6H-2-yl}Fe(PMe3)(3)(CCR) (R = Me, 4b-Me; R = Ph, 4b-Ph) were generated from lb. Exposure of lb to N2O or N(3)SO(2)tol generated 2b and Me3PO or Me3P=N(SO2)tol, respectively. Calculations revealed 2b to be thermodynamically and kinetically favored over the calculated Fe(III) superoxide complex, 3[Fe021, relative to 1b' + N-2 + O-2. The correlation of lb' + O-3(2) to (3)[FeO2] is likely to have a relatively high intersystem crossing point (ICP) relative to 1b' + N-2 to 2b, thereby explaining the dinitrogen selectivity.