Ni pincer complex catalytic hydroboration of CO2: a DFT study on the influence of borane reductants on selective reduction

Abstract

It has been reported that either the boryl formate (HCOOBR₂), bis(boryl)acetal (R₂BOCH₂OBR₂), or methoxy borane (R₂BOCH₃) product of CO₂ reduction is selectively afforded adopting the nickel (Ni) pincer catalyst by changing the properties of borane reductants. To obtain an insight into the influence of borane reductants on the selectivity of hydroboration of CO₂ catalyzed by (^tBuPCP)NiH, a density functional theory (DFT) computational study is performed with three different boranes (HBcat (catecholborane), 9-BBN (9-borabicyclo [3.3.1] nonane), and HBpin (pinacolborane)). The detailed formation and conversion of four-electron product R₂BOCH₂OBR₂ were considered for the first time, combining with the three sequential catalytic cycle mechanism, and the calculated results demonstrate that the distinctions of the electronic process in some key intermediates and transition states lead to the selectivity on products for different borane reductants.