Reduction of Carbon Oxides by an Acyclic Silylene: Reductive Coupling of CO

Reactions of a boryl‐substituted acyclic silylene with carbon dioxide and monoxide are reported. The former proceeds through oxygen atom abstraction, generating CO (with rearrangement of the putative silanone product through silyl‐group transfer). The latter is characterized by reductive coupling of CO to give an ethynediolate fragment, which undergoes formal insertion into the Si?B bond. The net conversion of carbon dioxide with two equivalents of silylene offers a route for the three‐electron reduction of CO₂ to [C₂O₂]^2?.     

Magnesium Boryl Reactivity with 9‐BBN and Ph3B: Rational B−B′ Bond Formation and Diborane Isomerization

Reactions of a magnesium‐based pinacolatoboryl nucleophile with the electrophilic organoboranes, 9‐BBN and Ph₃B, provide facile B−B′ single bond formation. Although the Ph₃B derivative is thermally stable, when heated, the unsymmetrical diborane(5) anion derived from 9‐BBN is found to isomerize to two regioisomeric species via a proposed mechanism involving dehydroboration of the borabicyclo[3.3.1]nonane and syn‐diboration of the resultant alkenyl carbocycle.