Methoxyl-substituted phosphine ligand properties and a case study of formation adducts to indium(III) bromide by DFT calculations

Abstract

Six bulky triphenylphosphine ligands containing substituted methoxyl groups (tris(2,4,6-trimethoxyphenyl)phosphine (TMP), tris(2,6-dimethoxyphenyl)phosphine (TDP), tris(o-methoxyphenyl)phosphine (o-Anis3P), tris(p-methoxyphenyl)phosphine (p-Anis3P), tris(m-methoxyphenyl)phosphine (m-Anis3P) and triphenylphosphine (PPh3)) were studied by DFT (density functional theory) calculations and experimental solution/solid-state 31P NMR spectroscopy. The basicity and binding ability of these substituted ligands, proven by comparison of structural data with DFT-predicted data, are in the order TMP > TDP > o-Anis3P > p-Anis3P > m-Anis3P > PPh3. Molecular structures for InBr3 with bulky ligands (TMP, TDP, o-Anis3P, p-Anis3P, m-Anis3P and PPh3) were calculated using DFT. P-In bond distances generated from these six optimized molecular structures and the calculated intramolecular interaction energies are in agreement with the ligand properties, with strong donation ability for those with the short bond distance; the In-P bond distance from shortest to longest follows a similar trend as predicted by DFT calculations. DFT calculations for these adducts show that methoxyl substitution to triphenylphosphine (PPh3) ligands contributed to its electron donor ability resulting in lower P-In bond distances with relatively large bond interaction energies.