NiII(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(sp2) and C(sp3) 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 NiII-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.

Division of Chemistry and Chemical Engineering Arthur Amos Noyes Laboratory of Chemical Physics California Institute of Technology Pasadena California 91125 United States

Division of Chemistry and Chemical Engineering The Warren and Katherine Schlinger Laboratory for Chemistry and Chemical Engineering California Institute of Technology Pasadena California 91125 United States

Institute of Organic Chemistry and Biochemistry Academy of Sciences of the Czech Republic Flemingovo náměstí 2 Prague 6 166 10 Czech Republic

J Heyrovský Institute of Physical Chemistry The Czech Academy of Sciences Dolejškova 3 Prague 8 182 00 Czech Republic

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