Unsymmetrical, Cyclic Diborenes and Thermal Rearrangement to a Borylborylene

Abstract

Cyclic diboranes(4) based on a chelating monoanionic benzylphosphine linker were prepared through boron-silicon exchange between arylsilanes and B Br . Coordination of Lewis bases to the remaining sp boron atom yielded unsymmetrical sp -sp diboranes, which were reduced with KC to their corresponding trans-diborenes. These compounds were studied with a combination of spectroscopic methods, X-ray diffraction, and DFT calculations. PMe -stabilized diborene 6 was found to undergo thermal rearrangement to gem-diborene 8. DFT calculations on 8 reveal a polar boron-boron bond, and indicate that the compound is best described as a borylborylene.

Phosphine‐Stabilized Diiododiborenes: Isolable Diborenes with Six Labile Bonds

“…The use of phosphine donors in place of carbenes is a more well‐established method to enhance the reactivity of diborenes; phosphine‐stabilized diborenes have shown quite diverse reactivity at different positions since their discovery in 2014. Unlike carbene‐stabilized diborenes, phosphine‐stabilized diborenes offer the additional opportunity (or hindrance) of labile B−P bonds, as demonstrated by a number of rearrangement processes both in the presence and absence of other reagents However, the B=B bond is also labile, and a number of reactions involving its cleavage have been presented, some of which are followed (or preceded) by B−P bond cleavage.…”

Coordination of Asymmetric Diborenes towards Cationic Coinage Metals (Au, Ag, Cu)

“…Very recently, we have developed two neutral asymmetric diborene derivatives 1 a and 1 b (Figure B), which potentially possess boryl borylene‐like natures ( 1 a′ , 1 b′ ) . The groups of Braunschweig and Jemmis propose that gem ‐diborenes would be regarded as boryl borylenes …”

“…[17] The groups of Braunschweig and Jemmis propose that gem-diborenes would be regardeda sb oryl borylenes. [18,19] In this article, we present the synthesis andX -ray diffraction analysiso faseries of asymmetricd iborene metal (Au, Ag, and Cu) complexes. The coordination properties of asymmetric diborenes to these metals are systematically discussed on the basis of theoretical calculations.…”

Konstruktion linearer und verzweigter Tetraborane durch 1,1‐ und 1,2‐Diborierung von Diborenen

“…Viele Arbeiten haben gezeigt, dass die Desymmetrisierung von Diboranen(4) [17a, 18] zu erhçhter Reaktivität, sowohl in der Aktivierung von kleinen Molekülen [19] als auch in Borylierungs-und Diborierungsreaktionen [20] sowie intramolekularen Umlagerungsprozessen [21] führt. Kürzlich berichteten wir über das Benzylphosphan-substituierte,u nsymmetrische Diboren 3 und sein gem-Isomer 4 (Schema 2), [22] (3) ) und 6 (1.856(4) )u nd damit im fürs p 3 -sp 3 -Diborane erwarteten Bereich, wobei der P1-B2-Abstand (1.911(8), 1.926-(8) )f üre ine P-B-dative-Bindung relativ kurz ist, was für eine hohe Lewis-Aciditätdes zentralen Boratoms spricht.…”