Bis(acetonitrile)bis(acetylacetonato)ruthenium(iii) mediated chemical transformations of coordinated 2-methylthioanilide

Abstract

Chemical reaction of [Ru^III(acac)₂(CH₃CN)₂]ClO₄ (1) with 2-methylthioaniline, HL¹ in ethanol under basic conditions yielded three new complexes Ru^II(acac)₂(L^1b) (1b), (L^1b = 4-imino-3-(methylsulfanyl)cyclohexa-2,5-dien-1-one), Ru^III(acac)₂(L^1c) (1c), (HL^1c = N-(2-methylthiophenyl)formamide) and (acac)₂Ru^II(μ-L^1d)Ru^II(acac)₂ (1d), (L^1d = 1,4-bis(2-methylthioaniline)-1,4-diazabutadiene) via the intermediate Ru^III(acac)₂(L^1a) (1a, L^1a = (L¹)⁻ = 2-methylthioanilide). The reaction proceeded through temperature induced valence tautomerisation between the Ru(III) center and its 2-methylthioanilide counterpart in 1a with concomitant reduction of ruthenium from +III to +II oxidation state and oxidation of ligand L^1a, resulting in aromatic ring hydroxylation, N-formylation and C–C bond formation reactions. All the complexes have been characterised by their single-crystal X-ray structure determination and various spectroscopic and electrochemical techniques. The identity of complex 1a has been confirmed by X-ray crystal structure determination of complex 2, a phenyl analogue of complex 1a. The complexes (1a–d) showed intense charge transfer (MLCT/LMCT) transition in the long wavelength region. The paramagnetic compounds, 1a and 1c, along with the diamagnetic compound 1b showed two one-electron responses in the ranges, −0.4 to −1.0 V and 0.3 to 1.1 V. The diamagnetic complex 1d displayed two successive one-electron reversible reductions (−1.31 and −1.55 V) and two one-electron reversible oxidation processes (−0.036 and 0.51 V). The redox processes are characterized by EPR spectroscopy and spectroelectrochemistry. The compound 1c has been found to exhibit solvatochromism and concentration dependent aggregation in solution.