Valence specific chelation of ruthenium to Schiff mono-bases of 2,6-diformyl-4methylphenol : synthesis and structure of trivalent salicylaldiminato species of coordination type RuN2O2PCl

Abstract The reaction of Schiff mono-bases, HRL (R = Me, Et), of 2,6-diformyl-4-methylphenol with K 2 RuCl,(H 2 O) has afforded Ru III (RL) 2 (PPh 3 )Cl. The X-ray structure of the R = Et complex has revealed metal chelation at the salicylaldimine segment of RL − , the two phenolic oxygen and azomethine nitrogen atoms lying in mutually trans and cis positions, respectively. The trivalent state of the metal is stabilized in Ru(RL) 2 (P-Ph 3 )Cl, the ruthenium (III)/ruthenium(II) E 1 2 being ∼0.40 V vs SCE. These distorted low-spin ( t 2 5 ) complexes display rhombic EPR spectra and are characterized by a pair of ligand field transitions (in the near-IR region) within the split t 2 shell. The complexes provide a striking contrast with the ruthenium(II) organometallics arising from the reaction of HRL with Ru II (PPh 3 ) 3 Cl 2.