Amines and boranes are the archetypical Lewis bases and acids, respectively. The former can readily undergo one-electron oxidation to give radical cations, whereas the latter are easily reduced to afford radical anions. Here, we report the synthesis of a neutral tricoordinate boron derivative, which acts as a Lewis base and undergoes one-electron oxidation into the corresponding radical cation. These compounds can be regarded as the parent borylene (H-B:) and borinylium (H-B(+.)), respectively, stabilized by two cyclic (alkyl)(amino)carbenes. Ab initio calculations show that the highest occupied molecular orbital of the borane as well as the singly occupied molecular orbital of the radical cation are essentially a pair and a single electron, respectively, in the p(π) orbital of boron.
The reaction of 2,2,3,3-tetrabromo-1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasilane with four equivalents of potassium graphite (KC8) in tetrahydrofuran produces 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyl-2-tetrasilyne, a stable compound with a silicon-silicon triple bond, which can be isolated as emerald green crystals stable up to 100 degrees C in the absence of air. The SiSi triple-bond length (and its estimated standard deviation) is 2.0622(9) angstroms, which shows half the magnitude of the bond shortening of alkynes compared with that of alkenes. Unlike alkynes, the substituents at the SiSi group are not arranged in a linear fashion, but are trans-bent with a bond angle of 137.44(4) degrees.
Organoborane compounds present a class of versatile synthetic intermediate for myriad organic transformations. The direct addition of a B−H bond across unsaturated bondnamely, hydro-borationis a powerful tool for the preparation of organoborane derivatives. This review outlines recent advances in catalytic hydroboration of unsaturated organic compounds, specifically those involving C-X (X = N, O) bonds. We will discuss the chemical behavior of both transition metal catalysts and main group catalysts in hydroboration. Emphasis will also be placed on the reaction mechanism of these catalytic reactions. Furthermore, recent achievements in catalytic hydroboration of carbon dioxide CO 2 will be highlighted.
A diverse array of nitrogen‐containing compounds were formed by the addition of hydrazine to alkynes, diynes, enynes, and allenes in the presence of cationic gold(I) complexes with a cyclic (alkyl)(amino)carbene ligand (see scheme; the X‐ray crystal structure of the gold–hydrazine complex is shown). This hydroamination is an ideal initial step for the preparation of acyclic and heterocyclic bulk chemicals. Dipp=2,6‐diisopropylphenyl.
Since the groundbreaking discovery
in 2018 that the synthesis of
a bottleable nucleophilic aluminyl anion is feasible, a handful of
derivatives have been developed to date, which are, however, limited
to diamino- and dialkyl-substituted species. Herein, we report the
synthesis of a cyclic (alkyl)(amino)aluminyl anion based on a five-membered
framework. The dicoordinate aluminum center features both a lone pair
of electrons and an unoccupied 3p orbital, thus genuinely making it
isoelectronic with carbenes. We show the bond formation and bond activation
at the Al sphere: thus, not only does it undergo electron redistribution
with borane to furnish a heteroatomic group 13 ring exhibiting a σ-aromatic
nature concomitant with a three-center two-electron AlB2 bond but also the ambiphilic nature allows for oxidative addition
of Si–H, N–H, and even C–C bonds at the aluminum
center.
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