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A unique recyclable Pd catalyst (‘SiO2’-NH2-Pd) for Suzuki-Miyaura coupling reaction of azaheteroaryl halides is developed. The catalytic system is working under mild aqueous condition with low Pd loading and without the use of phosphine ligand. The plausible mechanism is proposed based on the formation of undesired symmetrical biaryl from the coupling reaction of azaheteroaryl chlorides due to the oxidative homocoupling of nucleophilic arylboronic acid. This catalytic system represents an attractive and promising approach for the synthesis of azaheterobiaryls with high product yields. The catalyst has demonstrated an excellent recyclability.

Indole thiosemicarbazone ligands were prepared from indole-3-carboxaldehyde and N-(un)substituted thiosemicarbazide. The Ru(η6-p-cymene) complexes [Ru(η6-p-cymene)(HL1)Cl]Cl (1) and [Ru(η6-p-cymene)(L2)]2Cl2 (2*) were exclusively synthesized from thiosemicarbazone (TSC) ligands HL1 and HL2, and [RuCl2(p-cymene)]2. The compounds were characterized by analytical and various spectroscopic (electronic, FT-IR, 1D/2D NMR, and mass) tools. The exact structures of the compounds (HL1, HL2, 1, and 2*) were confirmed by single-crystal X-ray diffraction technique. In complexes 1 and 2*, the ligand coordinated in a bidentate neutral (1)/monobasic (2*) fashion to form a five-membered ring. The complexes showed a piano-stool geometry around the Ru ion. While 2* existed as a dimer, 1 existed as a monomer, and this was well explained through free energy, bond parameter, and charge values computed at the B3LYP/SDD level. The intercalative binding mode of the complexes with calf thymus DNA (CT DNA) was revealed by spectrosc...

A series of Ru(II)-benzene organometallic compounds (1–6) constructed from [RuCl2(η6-benzene)]2 and chiral aroylthiourea ligands (L1-L6) obtained from D/L-phenylalanine, was fully characterized. The chiral complexes along with 2-propanol and NaOH effected the asymmetric hydrogenation of aromatic ketones at 82 °C within 8–10 h. The reduction reactions proceeded with excellent conversions and enantiomeric excesses (up to 99%).

The new chiral ligands (R)-/(S)-N-((1-phenylethyl)carbamothioyl)benzamide (L1/L2), (R)-/(S)-N-((1-phenylethyl)carbamothioyl)thiophene-2-carboxamide (L3/L4), and (R)-/(S)-N-((1-phenylethyl)carbamothioyl)furan-2-carboxamide (L5/L6) were synthesized, characterized, and used to prepare novel chiral Ru(II) complexes. The chiral Ru(II) complexes 1–6 were obtained from reactions between the chiral ligands L1–L6 and [RuCl2(p-cymene)2]2. The complexes were characterized by analytical and spectroscopic (NMR, FT-IR, electronic) techniques. The solid-state structures of the ligands L1 and L3 and complexes 1, 4, and 6 were determined by single-crystal X-ray diffraction methods. In all of the complexes, the ligand is bound to the Ru(II) center only via the sulfur donor atom. This monodentate coordination of the acylthiourea ligands was observed for the first time with ruthenium. The Ru(II) complexes 1–6 all act as efficient catalysts for the asymmetric transfer hydrogenation of aromatic ketones in the presence of 2-pro...

Square planar palladium(II) complexes of the type [Pd(L)(PPh3)] (1–6) (where L is the dianion of N-(2-mercaptophenyl)salicylideneimine or 5-substituted-N-(2-mercaptophenyl)salicylideneimine or N-(2-mercaptophenyl)naphthylideneimine) have been synthesised from the reactions between [Pd(PPh3)4] and H2L in dichloromethane–ethanol mixture. The new complexes have been characterized by analytical and spectral (electronic, IR, 1H, 13C{1H} and 31P{1H} NMR spectroscopy) techniques. The structures of three complexes (1, 2 and 6) have been solved by single-crystal X-ray diffraction experiments which indicate square planar coordination geometries around palladium(II) by O, N, S and P donor atoms. The palladium(II) complexes (1–6) exhibited good catalytic activity in Suzuki–Miyaura cross-coupling reaction between phenylboronic acid and 4-bromotoluene in N,N-dimethylacetamide at 100 °C. Complex 3 (1 mol%) was found to be the most active and hence was used for probing the scope of possible substrates. Heterocyclic boronic acid and heterocyclic aryl bromides have also been used as substrates to provide heterocyclic biaryls.

Air stable Ni(II) and Pd(II) complexes viz. [Ni(LS)(P(OEt)3)] (1), [Ni(LN)(P(OEt)3)] (2), [Pd(LS)(P(OEt)3)] (3) and [Pd(LN)(P(OEt)3)] (4) [where LS and LN are dianions of N–(2–mercaptophenyl)salicylideneimine and N–(2–mercaptophenyl)naphthylideneimine respectively] have been synthesized and characterized by analytical and spectral (electronic, FT–IR, 1H, 13C and 31P NMR) methods. The 1H–31P HMBC spectrum established the coupling of phosphorus with the azomethine proton of the Schiff base and the aliphatic protons of triethylphosphite. Novel Ni(II) and Pd(II) complexes exhibited good catalytic activity in Kumada–Tamao–Corriu and Suzuki–Miyaura coupling reactions respectively.

2-[(E)-{(1S,2R)-1-hydroxy-1-phenylpropan-2-ylimino}methyl]phenol has been synthesized and its influence on corrosion of mild steel in 1 M HCl solution has been studied by means of weight loss and electrochemical measurements under various circumstances. The inhibitor showed a maximum of 91 % of inhibition efficiency at 100 ppm. Interestingly, the inhibition efficiency has decreased on increasing the inhibitor concentration. This abnormal behavior is attributed to the release of phenolic hydrogen from the molecule. The mechanism of corrosion inhibition follows Langmuir adsorption isotherm. The negative ∆G ads indicates the spontaneous adsorption of the inhibitor on mild steel surface. Potentiodynamic polarization studies show that it is a mixed type inhibitor with predominant cathodic inhibition. UV–Visible spectroscopy of the inhibitor and inhibitor adsorbed on the mild steel confirmed the chemical interaction of the inhibitor with the metal surface.

A series of 4-substituted N-(2-mercaptophenyl)salicylideneimine Schiff bases were synthesized and investigated for corrosion inhibition of mild steel in hydrochloric acid medium. Inhibition through adsorption mechanism is proposed for these inhibitors, which is well supported by electrochemical impedance spectroscopy, the Langmuir adsorption isotherm and Scanning Electron Microscope morphologies of inhibited and uninhibited mild steel specimens. The negative ∆Gads indicates the spontaneous adsorption of the inhibitor on a mild steel surface. Among all the examined inhibitors, 5-bromo-N-(2-mercaptophenyl)salicylideneimine showed a higher inhibition efficiency. In order to reveal the usefulness of these Schiff bases as corrosion inhibitors under various circumstances, weight loss measurements were performed at various temperatures, acid concentrations and immersion times.

Reactions of H2L with [RuHCl(CO)(PPh3)3] in toluene gives [Ru(L)(CO)(PPh3)2] (L = binegative tridentate ONS donor ligand derived from salicylaldehyde/4-substituted salicylaldehyde/2-hydroxy-1-naphthaldehyde and o-aminothiophenol) at room temperature. All the complexes were characterized by elemental analyses and UV–Visible, FT-IR, 1H, 13C and 31P NMR spectroscopic methods. 1H–1H COSY and 1H–31P HMBC spectra of [Ru(L4)(CO)(PPh3)2] have been studied. 1H–31P HMBC spectrum established the coupling of phosphorus atoms with azomethine proton. The single crystal X-ray analysis of [Ru(L5)(CO)(PPh3)2] revealed that Schiff base ligand is coordinated to the metal center, via dissociation of the two acidic protons, as a dianionic tridentate ONS donor and that ruthenium(II) ion adopts octahedral coordination with the phosphorus atoms in trans-disposition. Ruthenium complexes have been used in conjunction with N-methylmorpholine-N-oxide (NMO) for the catalytic oxidation of various alcohols at room temperature. Benzylic primary and secondary alcohols are oxidized in good to excellent yields, and aliphatic and cyclic alcohols give carbonyl compounds in moderate yields.

Five mononuclear nickel(II) complexes, viz. [Ni(L1)(PPh3)] (1), [Ni(L2)(PPh3)] (2), [Ni(L3)(PPh3)] (3), [Ni(L4)(PPh3)] (4) and [Ni(L5)(PPh3)] (5) (where L1, L2, L3, L4 and L5 are dianions of N-(2-mercaptophenyl)salicylideneimine, 5-methyl-N-(2-mercaptophenyl)salicylideneimine, 5-chloro-N-(2-mercaptophenyl)salicylideneimine, 5-bromo-N-(2-mercaptophenyl)salicylideneimine and N-(2-mercaptophenyl)naphthylideneimine, respectively), have been synthesized and characterized by means of elemental analysis, electronic, IR, 1H, 13C and 31P NMR spectroscopy. Single crystal X-ray analysis of two of the complexes (1 and 5) has revealed the presence of a square planar coordination geometry (ONSP) about nickel. The crystal structures of the complexes are stabilized by intermolecular π–π stacking between the ligands (L) and by various C–H···π interactions.