Trans-(P(OPh)3)2(CO)IrX (X = Cl and Br): When changing chloro to bromo doesn't make much difference

Complexes trans-(P(OPh)3)2(CO)IrX (X = Cl, Br) show coincidence in 31P NMR, IR carbonyl stretch, and UV-visible absorption properties. Modeling shows coincidence due to low-level halogen participation in key molecular orbitals, a balance between the halogen atom σ- and π-donation, and phenoxy group dominance of the phosphorus atom electronic structure.146