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A series of Cd(II) complexes, [(PPh3)2Cd(SCOf)2] (1), [PPh4]2[Cd(SCOf)2(μ-Br)]2 (2), [(PPh3)2Ag(μ2-SCOf)2Cd(SCOf)] (3), Na2[(PPh3)Cd(MeOH)(SCOf)3]2 (4a) and Na2[(PPh3)Cd(SCOf)3]2.C7H8 (4b) (Where SCOf = furan-2-thiocarboxylate), have been synthesized and characterized by single crystal X-ray analysis and other spectroscopic techniques. Complexes 1 and 2 show distorted tetrahedral and distorted trigonal bipyramidal geometries around Cd(II), respectively. In the case of 3, Cd(II) exhibits a trigonal prismatic structure, whereas, Ag(I) is at the center of a distorted tetrahedron. Complex 4, has a trigonal pyramidal geometry, hitherto unknown for a Cd(II) center. The catalytic activities of complexes for the synthesis of dihydropyrimidinone have been investigated. Out of four complexes, complex 4 is the most efficient catalyst for the one-pot multicomponent Biginelli-type coupling toward the synthesis of dihydropyrimidinone. Excellent yields of the desired products were obtained with very low catalyst loadings (1 mol%). With a few examples, the versatility and scope of the method have also been demonstrated. The catalysts were also tested for their recyclability. [ABSTRACT FROM AUTHOR]

Azobenzene-based unnatural amino acid motifs were synthesized via Pd(II)-catalyzed diastereoselective C(sp3)–H arylation of amino acid carboxamides with iodoacetanilides and Mills azo coupling. [ABSTRACT FROM AUTHOR]

Negishi cross‐coupling reaction of organozinc compounds as nucleophiles with aryl halides has drawn immense focus for C−C bond formation reactions. In comparison to the well‐established library of Pd complexes, the C−C cross‐coupling of this particular approach is largely primitive with nickel‐complexes. Herein, we describe the syntheses of Ni(II) complexes, [(MeBICAAC)2NiX2] (X=Cl (1), Br (2), and I (3)) by employing the bicyclic (alkyl)(amino)carbene (MeBICAAC) ligand. The reduction of complexes 1–3 using KC8 afforded the two coordinate low valent, Ni(0) complex, [(MeBICAAC)2Ni(0)] (4). Complexes 1–4 have been characterized by spectroscopic techniques and their solid‐state structures were also confirmed by X‐ray crystallography. Furthermore, complexes 1–4 have been applied in a direct and convenient method to catalyze the Negishi cross‐coupling reaction of various aryl halides with 2,6‐difluorophenylzinc bromide or phenylzinc bromide as the coupling partner in the presence of 3 mol % catalyst. Comparatively, among all‐pristine complexes, 1 exhibit high catalytic potential to afford value‐added C−C coupled products without the use of any additive. The UV‐vis studies and HRMS measurements of controlled stochiometric reactions vindicate the involvement of Ni(I)−NI(III) cycle featured with a penta‐coordinated Ni(III)‐aryl species as the key intermediate for 1 whereas Ni(0)/Ni(II) species are potentially involved in the catalytic cycle of 4. [ABSTRACT FROM AUTHOR]

This manuscript demonstrates the synthesis, structural characterization, computational studies, and biomimics of the phenazine oxidase activity of a newly designed cobalt (III) complex, [Co (dpa)(dpa‐H+)(N3)2]Cl2 (1) [dpa = 2,2′‐dipyridylamine] under an aerobic condition. The crystal structure analysis reveals that the cobalt (III) center adopts an octahedral geometry, and the complex forms a beautiful supramolecular framework through noncovalent interactions. The cobalt (III) catalyst turns out to be a promising catalyst for the oxidative coupling of o‐phenylenediamine (OPD) in oxygen‐saturated methanol with an excellent turnover number, kcat = 7.85 × 103 h−1. Spectrophotometric, electrochemical, mass spectrometry, and computational analysis ensure that the course of catalysis undergoes through a catalyst‐substrate complexation, facilitating the development of cobalt‐iminobenzoquinone species in the solution. The computational calculations employing the density functional theory (DFT) throw a light to the mechanistic insights of the phenazine oxidase mimics. ETS‐NOCV (extended transition state‐natural orbitals for chemical valence) plots of the reactive intermediates portray the coordination‐driven depletion of electron density from the nitrogens of OPD to cobalt center leading to the enhancement of electrophilic character on para‐positioned C‐atoms with respect to N‐atoms of OPD, therby catalyzing the nucleophilic attack by second OPD to produce the oxidation product, 2,3‐diaminophenazine (DAP). Interestingly, we are able to isolate the oxidation product of the OPD oxidation reaction as a hydrated chloride salt, DAPH+Cl− ·3H2O (2). The crystal engineering perspectives of 2 attribute the intriguing fate of the secondary chlorides for the stabilization of the oxidation product in crystalline phase. [ABSTRACT FROM AUTHOR]