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

Reinvestigation of trans-(P(OPh)3)2(CO)IrCl 1 and trans-(P(OPh)3)2(CO)IrBr 2 reveals unexpected coincidence in 31P NMR, IR carbonyl stretch, and UV–visible absorption properties. XRD structure studies show the complexes are isostructural, although the crystals are not isomorphous. The complexes were investigated via DFT and TD-DFT modeling which shows that the spectroscopic similarity can be attributed to low-level halogen orbital participation in key molecular orbitals, a balance between the halogen atom σ- and π-donation to the iridium center, and phenoxy group dominance of the phosphorus atom electronic structure. 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. [Display omitted] •Nearly identical spectra observed for (P(OPh)3)2(CO)IrX (X = Cl, Br).•DFT results used to analyze the near spectral coincidence.•IR spectral coincidence from balanced σ and π Ir–X interaction.•UV–visible absorption spectral coincidence from negligible X atom contribution.•31P NMR shift coincidence from dominance of the phenoxide groups.