Dinickel Catalyzed Vinylidene-Alkene Cyclization Reactions.

A dinickel catalyst promotes reductive cyclization reactions of 1,1-dichloroalkenes containing pendant olefins. The reactions can be conducted with a Zn reductant or electrocatalytically using a carbon working electrode. Mechanistic studies are consistent with the intermediacy of a Ni(vinylidene) species, which adds to the alkene and generates a metallacyclic intermediate.

Ni/Photoredox-Catalyzed Enantioselective Cross-Electrophile Coupling of Styrene Oxides with Aryl Iodides.

A Ni/photoredox-catalyzed enantioselective reductive coupling of styrene oxides and aryl iodides is reported. This reaction affords access to enantioenriched 2,2-diarylalcohols from racemic epoxides via a stereoconvergent mechanism. Multivariate linear regression (MVLR) analysis with 29 bioxazoline (BiOx) and biimidazoline (BiIm) ligands revealed that enantioselectivity correlates with electronic properties of the ligands, with more electron-donating ligands affording higher ee's.

Synthesis of β-Phenethylamines via Ni/Photoredox Cross-Electrophile Coupling of Aliphatic Aziridines and Aryl Iodides.

A photoassisted Ni-catalyzed reductive cross-coupling between tosyl-protected alkyl aziridines and commercially available (hetero)aryl iodides is reported. This mild and modular method proceeds in the absence of stoichiometric heterogeneous reductants and uses an inexpensive organic photocatalyst to access medicinally valuable β-phenethylamine derivatives. Unprecedented reactivity was achieved with the activation of cyclic aziridines.

Dinuclear oxidative addition reactions using an isostructural series of Ni, Co, and Fe complexes.

A family of low-valent Ni, Co, and Fe naphthyridine-diimine (NDI) complexes is presented. Ligand-based π* orbitals are sufficiently low-lying to fall within the metal 3d manifold, resulting in electronic structures that are highly delocalized across the conjugated [NDI]M system. This feature confers stability to metal-metal interactions during two-electron redox reactions, as demonstrated in a prototypical oxidative addition of allyl chloride.

Reversible substrate activation and catalysis at an intact metal-metal bond using a redox-active supporting ligand.

An electron rich Ni(I)-Ni(I) bond supported by a doubly reduced naphthyridine-diimine (NDI) ligand reacts rapidly and reversibly with Ph2SiH2 and Et2SiH2 to form stable adducts. The solid-state structures of these complexes reveal binding modes in which the silanes symmetrically span the Ni-Ni bond and exhibit highly distorted H-Si-H angles and elongated Si-H bonds. This process is facilitated by the release of electron density stored in the π-system of the NDI ligand.

Dinuclear nickel complexes in five states of oxidation using a redox-active ligand.

Redox-active nitrogen donor ligands have exhibited broad utility in stabilizing transition metal complexes in unusual formal oxidation states and enabling multielectron redox reactions. In this report, we extend these principles to dinuclear complexes using a naphthyridine-diimine (NDI) framework. Treatment of ((i-Pr)NDI) with Ni(COD)2 (2.