1,1-Hydroboration and Borane Adduct of Diphenyldiazomethane

Abstract

The advent of frustrated Lewis pair chemistry has demonstrated unique reactivity with a variety of small molecules. This thesis explores related chemistry with reactions of diazomethanes and highly electrophilic boranes. Diphenyldiazomethane Ph2C(N2) reacts with HB(C6F5)2 resulting in 1,1-hydroboration via a concerted reaction involving initial formation of the Lewis adduct, yielding the robust amino-borane product Ph2CN2BH(C6F5)2. Alternative synthetic routes to this product are detailed, as well as a related salt. Conversely, Ph2C(N2) reacts with B(C6F5)3 to form a highly sensitive adduct Ph2CN2B(C6F5)3. This product liberates N2 and is proposed to generate Ph2CB(C6F5)3. DFT calculations reveal that formation of this product is thermodynamically favourable from the starting compounds of carbene, N2 and borane. The isolation of this latter species opens the possibility that judicious choice of a Lewis acid and base could provide an avenue to metal-free fixation of N2.