1,3,2‐Diselenaborolanes with an Annelated Dicarba‐ closo ‐dodecaborane(12) Unit: Synthesis, Molecular Structure and Reactivity

"Homoleptic" Tetracoordinate Boron Compounds

"Homoleptic" tetracoordinate boron compounds, in which the central boron atom links to four identical atoms, are a special and important family of boron compounds. During the past decades, they have been extensively employed in inorganic, organic, macromolecular, and materials chemistry. Many of them exhibit a diverse range of outstanding properties, and therefore, the synthesis and application of those compounds have emerged as a hot research topic in modern boron chemistry. This review summarizes and discusses the "homoleptic" tetracoordinate boron compounds, which are organized according to the kinds of atoms coordinated to the central boron.

Unlocking Heteroaromatic Ring Systems through Chalcogen Insertion into Boroles

In this work, we report the reactivity of various annulated borole derivatives toward chalcogen (O, S, and Se) insertion. Among a series of 9-borafluorenes with different boron substituents (Ph, Br, or o-carboranyl) and a mixed thiophene-benzene-fused derivative, only the 9-o-carboranyl-substituted 9-borafluorene yielded the complete set of chalcogen-containing heteroarenes, including the first 1,2-selenaborinine derivative. To evaluate the aromaticity of this heterocyclic analogue of phenanthrene, nucleus-independent chemical shift (NICS) values were computed and compared to those of its lighter group 16 congeners.

Oxidative addition of elemental selenium to 1,4,2,5-diazadiborinine

A heavier analogue of dibora-peroxide 4 involving a B–Se–Se–B unit has been synthesized and fully characterized.

Closely related yet different: a borylene and its dimer are non-interconvertible but connected through reactivity

The self-stabilizing, tetrameric cyanoborylene [(cAAC)B(CN)]4 (I, cAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and its diborene relative, [(cAAC)(CN)B[double bond, length as m-dash]B(CN)(cAAC)] (II), both react with disulfides and diselenides to yield the corresponding cAAC-supported cyanoboron bis(chalcogenides). Furthermore, reactions of I or II with elemental sulfur and selenium in various stoichiometries provided access to a variety of cAAC-stabilized cyanoboron-chalcogen heterocycles, including a unique dithiaborirane, a diboraselenirane, 1,3-dichalcogena-2,4-diboretanes, 1,3,4-trichalcogena-2,5-diborolanes and a rare six-membered 1,2,4,5-tetrathia-3,6-diborinane. Stepwise addition reactions and solution stability studies provided insights into the mechanism of these reactions and the subtle differences in reactivity observed between I and II.

Reactivity of alkynylsilanes towards B-halogeno-1,3,2-diselenaborolanes with an annelated dicarba-closo-dodecaborane(12) unit

The C≡C bond of alkynylsilanes undergoes 1,2-haloboration with 2-halogeno-1,3,2-diselenaborolano-4,5-[1,2-dicarba-closo-dodecaborane(12)], in competition with reversible insertion into one of the B–Se bonds (selenoboration) to afford a seven-membered ring and finally, by elimination of Me3Si–X (X = Cl, Br, I), the corresponding B-alkynyl derivatives. The reactions were monitored by NMR spectroscopy (11B, 13C, 29Si and 77Se NMR). The proposed solution-state structures are also supported by DFT calculations of single molecule geometries and NMR parameters [B3LYP/6-311 + G(d,p) level of theory].