Regio- and Enantioselective Allylic Alkylation of Terminal Alkynes by Synergistic Rh/Cu Catalysis.

A highly branch- and enantioselective 1,4-enynes synthesis from readily available terminal alkynes and racemic allylic carbonates by Sonogashira type synergistic Rh and Cu catalysis under neutral conditions has been developed. Aliphatic and aromatic terminal alkynes with various functional groups could be used directly. An inner-sphere reductive elimination C(sp)-C(sp) bond formation mechanism is supported by the stoichiometric reaction.

Cobalt-Catalyzed Regio- and Enantioselective Allylic Alkylation of Malononitriles.

Cobalt-catalyzed highly branched- and enantioselective allylic alkylation of malononitriles has been developed. Chiral γ,δ-unsaturated malononitriles could be synthesized with >20:1 branched/linear regioselectivity and up to 99% enantiomeric excess from easily accessible racemic allylic carbonates under mild reaction conditions. The electron-rich and sterically less hindered bisoxazolinephosphine ligand is essential to realize the high reactivity in the carbon-carbon bond formation process.

Cobalt-Catalyzed Regio- and Enantioselective Allylic Amination.

The first earth-abundant cobalt-catalyzed highly branched- and enantioselective allylic amination of racemic branched allylic carbonates bearing alkyl groups with both aromatic and aliphatic amines has been developed. The process allows rapid access of allylic amines in high yields with exclusively branched selectivity and excellent enantioselectivities (normally 99% ) under mild reaction conditions.

Monoradical-containing four-coordinate Co(iii) complexes: homolytic S-S and Se-Se bond cleavage and catalytic isocyanate to urea conversion under sunlight.

Four-coordinate, monoradical-containing Co(iii) complexes participated in the non-innocent ligand driven homolytic cleavage of S-S and Se-Se bonds and catalyzed the conversion of RNCO (R = phenyl and naphthyl) to the corresponding urea derivatives (TON 480) in dry CHCl under sunlight stimulus.

Inter-ligand azo (N=N) unit formation and stabilization of a Co(II)-diradical complex via metal-to-ligand dπ-pπ* back donation: synthesis, characterization, and theoretical study.

An azide (-N3) group attached at the -ortho carbon atom to the aniline moiety of 2-anilino-4,6-di-tert-butylphenol formed a diradical-containing Co(II) complex via inter-ligand azo (N=N) bond formation. Metal-to-ligand (azo), dπ-to-pπ* back donation stabilized the metal in its lower oxidation state.

Copper(II)-mediated transformation of a tridentate non-innocent ligand into a tetradentate salen-type innocent ligand.

A non-innocent ligand, H4L(CH2NH2), was synthesized by introducing a -CH2NH2 group at the ortho carbon atom to the aniline moiety of 2-anilino-4,6-di-tert-butylphenol. The new ligand was characterized by IR and NMR spectroscopy and mass spectrometry techniques. Upon treatment with CuCl2⋅2H2O, this non-innocent ligand provided a mononuclear four-coordinate salen-type Cu(II) complex by complete modification of the ligand backbone.

Effect of ligand substituent coordination on the geometry and the electronic structure of Cu(II)-diradical complexes.

Two organic moieties, known as ligands, having -OMe and -SePh as the ortho substituent attached to the aniline moiety of the parent 2-anilino-4,6-di-tert-butylphenol ligand, were synthesized. The ligands reacted with CuCl2·2H2O in a 2:1 ratio in CH3CN in the presence of Et3N and provided the corresponding mononuclear Cu(II)-diradical complexes 1 (-OMe) and 2 (-SePh). Complex 1 was square planar, while complex 2 was in distorted square planar geometry due to the secondary coordination between the Se atom and the central Cu(II) center.

Effect of ligand substituent on the reactivity of Ni(II) complexes towards oxygen.

Two radical-containing Ni(II) complexes having either parent salicylidene (complex 1) or 3,5-di-tert-butylsalicylidene (complex 2) in the ligand backbone were synthesized. Complex 2 underwent ligand centered C–H activation by aerial oxygen, forming the corresponding amide complex (2a). The UV-Vis/NIR spectral changes upon purging of molecular oxygen to 2 in CH2Cl2, alongwith ESI-MS analysis indicated the generation of Ni–oxygen/dioxygen species as the intermediate(s) for the amide formation.

Ortho-substituent induced triradical-containing tetranuclear oxo-vanadium(IV) cluster formation via ligand C-N bond breaking and C-O bond making.

Substituent having weak-coordination character, and attached at the ortho-carbon atom to the aniline moiety of 2-anilino-4,6-di-tert-butylphenol, provided a triradical-containing tetranuclear vanadium(IV) complex via ligand C-N bond breaking and C-O bond making.