Isolation of diborenes and their 90°-twisted diradical congeners

Abstract

Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound.

Methylbismuth: an organometallic bismuthinidene biradical

“…Simulations based on DFT and multi-reference calculations were carried out for 3 , 4 and 5 . While DFT often provides very accurate geometries and frequencies even for molecules with complicated electronic structures, 48 it is in many cases less accurate for the computation of energy surfaces or excitation energies. 49 Hence, the ωB97X-D3 50 functional was employed for frequency computations, but the multi-reference NEVPT2 51 approach was used to determine geometrical changes and to compute ionization energies as well as the energy difference between the two relevant states of the [BiCH 3 ] •+ cation ( vide infra ).…”

Reduction of a dihydroboryl cation to a boryl anion and its air-stable, neutral hydroboryl radical through hydrogen shuttling

“…Unlike in 5 and 5-thf, the B1-C1 and C1-N1 bonds at the neutral CAAC Me ligand (1.5174(18) and 1.4601(18)Å, respectively) are within the range typical of partial double bonds, as is typical for CAAC-stabilised boryl radicals due to the delocalisation of the unpaired electron over the N1-C1-B1 p framework. [5][6][7][8][9]21,22,[31][32][33] The IR spectrum of 6 shows a B-H stretching band at 2533 cm À1 (calc. : 2558 cm À1 at uB97XD/6-31+G*), ca.…”

Hydrophosphination of boron–boron multiple bonds

“…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.…”