Ligand concentration and reaction time controlled successive substitution of chloro and η6-benzene of di-μ-chlorobis{η6-benzene)dichlororuthenium(II)} with selenated Schiff base: Formation of half sandwich Ru(II) complex highly active catalyst for oxidation of alcohols

Schiff base (L) synthesized by reacting 2-methylthiobenzeldehyde with 2-(phenylseleno)ethylamine on reaction with di-mu-chlorobis{eta(6)-benzene)dichloro-ruthenium(II)}(a) forms two type of species: (i) [Ru(L)(2)][PF6](2) (1) [L:a = 4:1 and reaction time similar to 8 h] and (ii) [Ru(eta(6)-C6H6)(L)][PF6](2) (2) [L:a = 2:1 and reaction time similar to 1 h]. This is first example in which chloro as well benzene ring both are successively substituted by controlling metal:ligand ratio and duration of reaction. The geometry around Ru in complex 1 is distorted octahedral. The 2 has a pseudo-octahedral half sandwich piano-stool disposition of ligands around Ru. The Ru-Se distances are 2.4683(10)-2.5082(7) angstrom. The proton and carbon-13 NMR spectra of L and its both complexes I and 2 authenticate them. The 2 shows high catalytic activity for oxidation of primary and secondary alcohols both (TON upto 9.6 x 10(4); TOF upto 4.80 x 10(4) h(-1)). (C) 2009 Elsevier B.V. All rights reserved.