Pyridine-2-olato bridged dirhodium(III) acyl organometallics: Synthesis, spectroscopic, structural and theoretical studies

Abstract

The heterogeneous phase reaction of [Rh(MeLsb)(PPh3)2Cl2] (1) with the sodium salt of three different pyridine-2-olato ligands [Na(R‒Opy), R = H, Me, NO2] in dichloromethane–acetone–water medium afforded the complexes of type [Rh(Lal)(PPh3)(R-Opy)]2 (2(R)) in excellent yield. These are the first examples of dirhodium(III) acyl complexes with the bridging pyridine-2-olato ligand. The penta coordinated dirhodium(III) acyl complexes are formed by the cleavage of the RhCl and RhPPh3 bonds of the precursor complex 1. The two R-Opy ligands bridge the two rhodium centers through their OOpy donor centers. The conversion of 1→2(R) is attended with the concomitant hydrolysis of the aldiminium function in 1. The spectral (UV–vis, IR, NMR) data of the complexes are reported. The identity of 2(Me) has been established by single crystal X–ray structure determination which revealed distorted trigonal bipyramidal RhCNO2P coordination sphere. The Rh, C, N and Ophenolato atoms define the equatorial plane whereas Rh, OOpy and P atoms define the axial plane. The electronic structures and absorption spectra of the complexes are also scrutinized by the density functional theory (DFT) and time–dependent DFT calculations.