VALENCE SPECIFIC CHELATION OF RUTHENIUM TO SCHIFF MONO-BASES OF 2,6-DIFORMYL-4-METHYLPHENOL - SYNTHESIS AND STRUCTURE OF TRIVALENT SALICYLALDIMINATO SPECIES OF COORDINATION TYPE RUN2O2PCL

The reaction of Schiff mono-bases, HRL (R = Me, Et), of 2,6-diformyl-4 -methylphenol with K-2 RuCl5(H2O) has afforded Ru-III(RL)(2)(PPh3)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 az omethine nitrogen atoms lying in mutually trans and cis positions, res pectively. 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 similar to 0. 40 V as SCE. These distorted low-spin (t(2)(5)) complexes display rhom bic EPR spectra and are characterized by a pair of ligand field transi tions (in the near-IR region) within the split t(2) shell. The complex es provide a striking contrast with the ruthenium(II) organometallics arising from the reaction of HRL with Ru-II(PPh3)(3)Cl-2. (C) 1997 Els evier Science Ltd.