A four-membered C,O-chelate : Two families of ruthenium organometallics incorporating N ... O hydrogen bonding

Article abstract of DOI:10.1016/S0277-5387(96)00390-7

The reaction of mono-Schiff bases of 4-methyl-2,6-diformylphenol and primary amines (p-XC₆H₄NH₂, X = OMe, Cl, CO₂Et and NO₂) with Ru(PPh₃)₃Cl₂ in boiling ethanol afforded violet diamagnetic complexes, [Ru(η²:-p-XC₆H₄L) (PPh₃)₂(CO)Cl] (η²-p-XC₆H₄L = [4-methyl-6-(N-p-Xphenyliminiomethyl) phenolato-C²,O] incorporating the unprecedented orthoruthenated phenolato function, which is hydrogen-bonded with the uncoordinated imine nitrogen. These complexes were found to react with sodium benzoates (p-ZC₆H₄COO, Z = Me, Cl) to generate the new aryl complexes of ruthenium. [Ru(η¹-p-XC₆H₄L)(P-Ph₃) ₂(CO)(η²-p-ZC₆H₄COO)]. The spectral (IR, UV-vis and ¹H NMR) features of these two types of complexes and the effect of the X substituent on electronic and ¹H NMR spectra are scrutinized. The effect of PPh₃ ring currents on the chemical shifts of the metallated ring protons is semiquantitatively estimated. In these complexes different types of novel intramolecular N ... O interaction and the conformational orientation of p-XC₆H₄L ligands are noted. The redox behaviour of these complexes is reported. The E_{1 2} values of Ru^III/Ru^II couple correlate linearly with the Hammett constants (σ) of X substituent in the halo complexes. A spectroelectrochemical correlation in these complexes is also observed. Copyright