Fundamental organometallic chemistry under bimetallic influence: driving ß-hydride elimination and diverting migratory insertion at Cu and Ni.

Bimetallic effects on stoichiometric ß-hydride elimination and migratory insertion reactions were examined. Bimetallic reaction conditions drove ß-hydride elimination at Cu, while bimetallic C-B elimination occurred in the absence of ß-hydrogens. The inherent migratory insertion chemistry of alkynes at Ni was diverted under bimetallic reaction conditions to favor C-H deprotonation.

Thermal C-H borylation using a CO-free iron boryl complex.

New CO-free iron boryl complexes, CpFe(PR3)2(Bpin), are described. The CpFe(PEt3)2(Bpin) derivative is uniquely capable of UV-free arene borylation at 70 °C via a dissociative pathway. Catalytic C-H borylation does not proceed using either monometallic or heterobimetallic schemes, and this failure is rationalized through analysis of relative pKa values for the corresponding iron hydride species.

Base metal catalysts for photochemical C-H borylation that utilize metal-metal cooperativity.

Heterobimetallic Cu-Fe and Zn-Fe complexes catalyze C-H borylation, a transformation that previously required noble metal catalysts. The optimal catalyst, (IPr)Cu-FeCp(CO)2, exhibits efficient activity at 5 mol% loading under photochemical conditions, shows only minimal decrease in activity upon reuse, and is able to catalyze borylation of a variety of arene substrates. Stoichiometric reactivity studies are consistent with a proposed mechanism that exploits metal-metal cooperativity and showcases bimetallic versions of the classical organometallic processes, oxidative addition and reductive elimination.