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 oxidati

Schiff base (L) synthesized by reacting 2-methylthiobenzeldehyde with 2-(phenylseleno)ethylamine on reaction with di-μ-chlorobis{η6-benzene)dichloro-ruthenium(II)}(a) forms two type of species: (i) [Ru(L)2][PF6]2 (1) [L:a = 4:1 and reaction time ∼8 h] and (ii) [Ru(η6-C6H6)(L)][PF6]2(2) [L:a = 2:1 and reaction time ∼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) Ǻ. The proton and carbon-13 NMR spectra of L and its both complexes 1 and 2 authenticate them. The 2 shows high catalytic activity for oxidation of primary and secondary alcohols both (TON upto 9.6 × 104; TOF upto 4.80 × 104 h−1).

Graphical abstractSchiff base (L) obtained by reacting 2-methylthiobenzeldehyde with 2-(phenylseleno)ethylamine on reaction with di-μ-chlorobis{η6-benzene)dichloro ruthenium(II)}(a) forms [Ru(L)2][PF6]2 (1) when L:a = 4:1 and stirring time of reactants 8 h whereas for L:a = 2:1 and stirring time 1 h the complex formed is [Ru(η6-C6H6)(L)][PF6]2 (2). The geometry around Ru in complex 1 is distorted octahedral. The 2 exhibits the pseudo-octahedral half sandwich “piano-stool” disposition around Ru. The Ru–Se distances are 2.4683(10)–2.4683(10) Ǻ. The 2 shows high catalytic activity for oxidation of alcohols (TON upto 9.6 × 104).Figure optionsDownload full-size imageDownload as PowerPoint slide