Ruthenium–carbonyl complexes of 1-alkyl-2-(arylazo)imidazoles: Synthesis, structure, spectra and redox properties

trans-(Cl)-[Ru(CO)2Cl2(PaiR/TaiR)] compounds have been synthesized by reacting 1-alkyl-2-(phenylazo)imidazole (PaiR) or 1-alkyl-2-(p-tolylazo)imidazoles (TaiR) with [Ru(CO)2Cl2]n in methanol under refluxing conditions. The X-ray crystallographic study of trans-(Cl)-[Ru(CO)2Cl2(PaiEt)] (PaiEt = 1-ethyl-2-(phenylazo)imidazole) shows a distorted octahedral geometry with a trans-Cl,Cl configuration. An intermolecular hydrogen bonded dimer serves as a motif in the supramolecular network with C–H⋯π and π⋯π interactions. The complexes show metal oxidation, Ru(III)/Ru(II); and reduction of the coordinated azo (–NN–) function. The molecular orbital diagram has been drawn by density functional theory (DFT) using an optimized geometry from the single crystal X-ray parameters. The electronic movement and assignment of electronic spectra have been carried out by TD-DFT calculations both in the gas and acetonitrile phase.

[Ru(CO)2Cl2(PaiR/TaiR)] are described in this work where PaiR or TaiR are 1-alkyl-2-(arylazo)imidazoles, acting as imidazole-N, azo-N chelating agents. One of the structures, [Ru(CO)2Cl2(PaiEt)], has been characterized by its X-ray structure determination, which shows a trans-(Cl,Cl) arrangement. Addition of excess Me3NO has synthesized the mono-carbonyl complex, [Ru(CO)Cl2(PaiR/TaiR)(NCMe)]. The electronic spectra and redox properties of the complexes have been supported by DFT and TD-DFT calculations.Figure optionsDownload as PowerPoint slide