Steric and Electronic Manipulation of the Agostic and π‐Syndetic Donations in a Known Iminophosphane Ni(II) Complex Containing a Rotatable In‐Plane Aromatic Ring

Abstract

AbstractDensity functional theory (DFT) calculations show that in a known nickel(II) complex containing a chelating iminophosphane ligand, where a pendant aromatic ring forms a weak agostic interaction with the metal centre, significant π‐syndetic donation is developed which establishes this kind of donation in a complex derived from experiment. Electron withdrawing and donating groups added to the carbon para to the agostic carbon do not cause the aromatic ring to rotate. Natural bond orbital (NBO) analysis shows that electron withdrawing groups cause little change to the agostic and π‐syndetic donations but electron donation switches off the π‐syndetic donation forming η1‐complexes of varying strength but which still retain a mostly unchanged agostic component. Increasing the size of the substituent ortho to the agostic carbon sequentially, cause rotation of the ring whereby the agostic donation declines slowly, the π‐syndetic donation rises followed by a rapid decline in both donations. The study shows that both donations may be manipulated where a rotatable aromatic ring is present.