Chemistry of boron and silicon subhalides

Abstract

Until recently, the use of high temperatures (>1000°) has held few attractions for the majority of synthetic chemists concerned with compounds stable only under moderate conditions. This situation has begun to change with more widespread use of a sim-

Reactivity of terminal transition metal borylene complexes

“…The quest for molecules that would display similar properties has identified borylenes, B R, as excellent candidates [1][2][3]. However, the known instability and consequent high reactivity of borylenes as free molecules [4] mean that transition metal borylene complexes are challenging targets of long standing for synthetic chemists [5 11]. During the past 15 years, renewed interest in the chemistry of transition metal complexes of boron made possible, for the first time, to generate and stabilize borylenes in the coordination sphere of various transition metals.…”

Trapping the Elusive Parent Borylene

“…Various more-or-less successful trapping approaches have been developed to substantiate their existence, some of which subsequently having been disputed. [2] These approaches include high-temperature reactions, [3] the photolytic cleavage of BÀE bonds, [4] and inter- [5] and intramolecular [6] reductive dehalogenation reactions, which all suffered either from 1) poor analytical data for the resulting species, 2) harsh reaction conditions, and/or 3) low selectivity and yields of isolated products. They all failed to provide the ultimate evidence for the existence of free borylenes.…”

Coordination and Activation of the BF Molecule

“…[5] Among this family of simple diatomic molecules, fluoroborylene (BF) offers a stark contrast to both N 2 and CO, being an exotic species known only at extreme temperatures or in high vacuum, and as yet eluding structural characterization as a ligand in a simple metal complex. [6] In part, the steady increase in lability along the series of diatomic molecules N 2 , CO, BF reflects the decreasing energy difference between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO gap) and increasing bond polarity. [7] Notwithstanding this, quantum chemical studies have predicted BF to form stronger bonds to transition-metal centers than either N 2 or CO, principally owing to improved s-donor capabilities.…”