Mechanistic investigations of the Ni-catalyzed asymmetric reductive alkenylation of N-hydroxyphthalimide (NHP) esters and benzylic chlorides are reported. Investigations of the redox properties of the Ni-bis(oxazoline) catalyst, the reaction kinetics, and mode of electrophile activation show divergent mechanisms for these two related transformations. Notably, the mechanism of C(sp 3 ) activation changes from a Nimediated process when benzyl chlorides and Mn 0 are used to a reductant-mediated process that is gated by a Lewis acid when NHP esters and tetrakis(dimethylamino)ethylene is used. Kinetic experiments show that changing the identity of the Lewis acid can be used to tune the rate of NHP ester reduction. Spectroscopic studies support a Ni II −alkenyl oxidative addition complex as the catalyst resting state. DFT calculations suggest an enantiodetermining radical capture step and elucidate the origin of enantioinduction for this Ni-BOX catalyst.

Treating a family of uranium benzyl compounds, Tp*2U­(CH2Ph) (1-Bn), Tp*2U­(CH2-para- i PrPh) (1- i Pr), Tp*2­U­(CH2-para- t BuPh) (1- t Bu), or Tp*2­U­(CH2-meta-OMePh) (1-OMe), which are supported by two hydro­tris­(3,5-di­methyl­pyra­zolyl)­borate (Tp*) ligands, with a single equivalent of triphenylphosphine oxide (OPPh3) causes a unique carbon–carbon coupling to occur. The products of this reaction, Tp*2U­[OP­(C6H5)2­(C6H5­CH2­C6H5)] (2-Ph), Tp*2U­[OP­(C6H5)2­(C6H5­CH2-p-iPr­C6H4)] (2- i Pr), Tp*2U­[OP­(C6H5)2­(C6H5­CH2-p-tBu­C6H4)] (2- t Bu), and Tp*2U­[OP­(C6H5)2­(C6H5­CH2-m-OCH3­C6H4)] (2-OMe), are characterized by coupling between the benzyl substituent and the para-carbon of one of the phenyl groups of OPPh3. To probe the scope of this unusual reactivity, 1-Bn was treated with different tris­(aryl)­phos­phine oxides, including tris­(p-tolyl)­phos­phine oxide, which yields Tp*2U­[OP­(p-tolyl)2­(C6H4­(CH3)­CH2­C6H5)] (3-tolyl). All compounds were characterized by multinuclear NMR, vibrational, and electronic absorption spectroscopies. When possible, X-ray diffraction was used to confirm molecular structures.

Herein, we report aC u-catalyzed enantioselective allylic alkylation using a g-butyrolactone-derived silyl ketene acetal. Critical to the development of this work was the identification of an ovel mono-picolinamide ligand with the appropriate steric and electronic properties to affordt he desired products in high yield (up to 96 %) and high ee (up to 95 %). Aryl, aliphatic,a nd unsubstituted allylic chlorides bearing ab road range of functionality are well-tolerated. Spectroscopic studies reveal that aC u I species is likely the active catalyst, and DFT calculations suggest ligand sterics play an important role in determining Cu coordination and thus catalyst geometry.

Ni II (IB) dihalide [IB = (3aR,3a′R,8aS,8a′S)-2,2′-(cyclopropane-1,1-diyl)bis(3a,8a-dihydro-8H-indeno[1,2-d]-oxazole)] complexes are representative of a growing class of first-row transition-metal catalysts for the enantioselective reductive cross-coupling of C(sp 2 ) and C(sp 3 ) electrophiles. Recent mechanistic studies highlight the complexity of these ground-state cross-couplings but also illuminate new reactivity pathways stemming from one-electron redox and their significant sensitivities to reaction conditions. For the first time, a diverse array of spectroscopic methods coupled to electrochemistry have been applied to Ni II -based precatalysts to evaluate specific ligand field effects governing key Ni-based redox potentials. We also experimentally demonstrate DMA solvent coordination to catalytically relevant Ni complexes. Coordination is shown to favorably influence key redox-based reaction steps and prevent other deleterious Ni-based equilibria. Combined with electronic structure calculations, we further provide a direct correlation between reaction intermediate frontier molecular orbital energies and cross-coupling yields. Considerations developed herein demonstrate the use of synergic spectroscopic and electrochemical methods to provide concepts for catalyst ligand design and rationalization of reaction condition optimization.

The "trilobite"-type of molecule, predicted in 2000 and observed experimentally in 2015, arises when a Rydberg electron exerts a weak attractive force on a neutral ground state atom. Such molecules have bond lengths exceeding 100 nm. The ultralong-range chemical bond between the two atoms is a nonperturbative linear combination of the many degenerate electronic states associated with high principal quantum numbers, and the resulting electron probability distribution closely resembles a fossil trilobite from antiquity. We show how to coherently engineer this same long-range orbital through a sequence of electric and magnetic field pulses even when the ground-state atom is not present and propose several methods to observe the resulting orbital. The existence of such a ghost chemical bond in which an electron reaches out from one atom to a nonexistent second atom is a consequence of the high level degeneracy.