Construction of Linear and Branched Tetraboranes by 1,1‐ and 1,2‐Diboration of Diborenes

Abstract

Sterically unencumbered diborenes based on abenzylphosphine chelate undergo diboration reactions with bis-(catecholato)diboron in the absence of ac atalyst to yield tetraboranes.T he symmetrical diborenes studied undergo 1,2diborations,whereas an unsymmetrical derivative was found to yield at riborylborane-phosphine adduct as the result of af ormal 1,1-diboration. Ar elated borylborylene compound also underwent a1,2-diboration to produce aborylene-borane adduct.

Hydrophosphination of boron–boron multiple bonds

“…37 Whereas one might expect such a compound to undergo 1,1-addition reactions to the "borylene" boron atom, both 4 (ref. 33) and a related compound reported by Kinjo's group 44 give 1,2-addition products with B 2 cat 2 . Compound 4 reacts instantaneously with HPPh 2 upon solvation in C 6 D 6 to give different NMR signals to those seen in the corresponding reaction with 2.…”

“…39,40 We have previously shown that unsymmetrical diborenes 2 and 3 (Scheme 2) react more quickly than 1 in diboration reactions with B 2 cat 2 . 33 Treatment of compound 2 with HPPh 2 resulted in complete conversion to a new compound within 3 h at room temperature. Signals in the 11 B NMR spectrum at À7.7 and À34.2 ppm again indicated the presence of inequivalent, four-coordinate boron atoms.…”

“…Whereas P-H bond activation at transition 25 and main-group 26 metal centres is well documented, to the best of our knowledge the sole reported example of hydrophosphination of a homonuclear double bond comprising elements other than carbon is the 2016 report by Wang and Wu of hydrophosphination of the N]N bond in azobenzene with diphenylphosphine oxide. 27 Recent studies in our laboratories have demonstrated the feasibility of adding H-H, 28,29 B-H, [30][31][32] B-B, 33,34 S-S 35,36 and Se-Se 35 bonds across boron-boron multiple bonds. In this work, we show that uncatalysed hydrophosphination of both diborenes and diborynes can be used as a mild, selective and catalyst-free route to construct B-P bonds.…”

Bond‐Strengthening Backdonation in Aminoborylene‐Stabilized Aminoborylenes: At the Intersection of Borylenes and Diborenes

“…Nonsymmetric diborenes featuring both donor moieties on the same boron atom have also emerged very recently in the literature (Figure ; B ) . Such species display distinct reactivity, including 1,2‐addition reactions and unsymmetrical coordination to transition‐metal centers, both of which underscore the polarization of the B−B π‐bond toward the doubly ligated boron center. Computational investigations have revealed the electronic ground state of such species as having significant contribution from a (boryl)borylene‐type resonance structure, which suggests that desymmetrization of the reduced B 2 moiety results in borylene‐like reactivity …”

Isolierung neutraler, mono‐ und dikationischer B2P2‐Ringe durch Addition eines Diphosphans an eine Bor‐Bor‐Dreifachbindung

“…Zusammenfassend haben wir eine Synthesestrategie entwickelt, um die ersten NHC-stabilisierten cyclo-B 2 P 2 -Verbindungen über die Addition einer Phosphor-Phosphor-Bindung an eine Bor-Bor-Dreifachbindung eines Diborins herzustellen. Im Gegensatz zu den aufgezeigten Reaktionen von anderen unpolaren E-E-Bindungen mit NHC-stabilisierten Diborinen [14] lagert sich das 1,2-Additionsprodukt eines Diphosphans, namentlich das Diphosphinodiboren 1, zu dem Produkt mit einem B 2 P 2 -heterocyclischen Kern 2 um. Verbindung 2 ist anfällig dafür, abhängig von der Natur der Re- 4 ] 2 mit Schwingungsellipsoiden einer Aufenthaltswahrscheinlichkeit von 50 % entsprechend.…”