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Abstract: The reaction of 1-alkyl-2-{(o-thioalkyl)phenylazo}imidazoles (SRaaiNR) (2a/2b) with Ru(II) has synthesized [Ru(SRaaiNR)2](ClO4)2 (3a/3b) in 2-methoxyethanol. The reaction in methanol, however, has synthesized [Ru(SRaaiNR)( S RaaiNR)Cl](ClO4) (4a/4b). The solid phase reaction of SRaaiNR and RuCl3 on silica gel surface upon microwave irradiation has synthesized [Ru(SRaaiNR)(SaaiNR)](PF6) (5a/5b) [SRaaiNR represents tridentate N,N′,S-chelator; S RaaiNR is N,N′-bidentate chelator where S does not coordinate and SaaiNR refers N,N′,S-chelator where S refers to thiolato binding]. The structural characterization of [Ru(SEtaaiNEt)( S EtaaiNEt)Cl](ClO4) (4b) and [Ru(SEtaaiNEt)(SaaiNEt)](PF6) (5b) has been confirmed by single crystal X-ray diffraction study. The IR, UV–Vis, and 1H NMR spectral data also support the stereochemistry of the complexes. The complexes show metal oxidation, Ru(III)/Ru(II), and ligand reductions (azo/azo−, azo−/azo ). The molecular orbital diagram has been drawn by density functional theory (DFT) calculation. Normal mode of analysis has been performed to correlate calculated and experimental frequencies of representative complexes. The electronic movement and assignment of electronic spectra have been carried out by TDDFT calculation both in gas and acetonitrile phase. [Copyright &y& Elsevier]

Abstract: The reaction of 2-(3′-pyridylazo)imidazole (PyaiH) or 1-alkyl-2-(3′-pyridylazo)imidazole (PyaiR) with in THF or MeCN has synthesized stable red coloured (2a) or (2b–2d). While the reaction of PyaiR and in dry n-heptane has separated shining green compound and has been identified azo-anion radical, [Os(Cl)(CO)(PPh3)2(PyaiR− )] (4b–4d). The reaction performance in n-hexane or toluene is very poor. Upon addition of Cl2 in MeCN to CH2Cl2 solution of 2 or 4 the colour has changed sharply to red-violet and has isolated (3). The reaction of 2 in ethanol with NaBH4 suspension under dinitrogen has reduced coordinated imidazole group to imidazolidine (5). One of the structures of azo-imidazolidinate-hydrido-osmium–carbonyl, [Os(H)(CO)(PPh3)2(PyaiH2)] (5a), is characterized by X-ray diffraction study. Other spectroscopic studies (IR, UV–Vis, NMR) are used to identify the structure of all the complexes. Electrochemistry shows two consecutive anodic peaks (E pa) and suggest irreversible oxidations Os(III)/Os(II), Os(IV)/Os(III) along with azo reductions. [Copyright &y& Elsevier]