The reactions of organic azides with diaryl­(dihalo)­diboranes(4) were explored, resulting in the observation of a number of surprising reactivity patterns. The reaction of phenyl azide with 1,2-diaryl-1,2-dihalodiboranes(4) resulted in the formation of five-membered rings comprising diboryl-triazenes with retention of the boron–boron bond, while the reaction of the peculiar 1,1-di­(9-anthryl)-2,2-difluorodiborane(4) with phenyl azide yielded a six-membered ring bearing a diboryl-triazene, whereby the B–B bond was ruptured by the insertion of an arylnitrene-like reactive intermediate. Both types of heterocycles feature unprecedented connectivity patterns and are very rare examples of boryl triazenes beyond the more common 1,2,3-triazolatoboranes. They are also the product of a unique type of aryl migration from a boron center to the phenyl azide γ-nitrogen center. Lastly, the substitution of 1,2-diaryl-1,2-dihalodiboranes(4) with azide groups, using trimethylsilyl azide as the transfer reagent, yielded boryl-tetrazaboroles and diboryldiazadiboretidines (as side-products), invoking the intermediacy of the first N-boryl-substituted iminoboranes, which are BN isosteres of monoborylated alkynes. The synthetic results are complemented with mechanistic proposals derived from quantum-chemical calculations.

Herein we report the discovery that two bottleable, neutral, base-stabilized diborane(5) compounds are able to bind strongly to a number of copper(I) complexes exclusively through their B-B bond. The resulting complexes represent the first known complexes containing unsupported, neutral σ diborane ligands. Single-crystal X-ray analyses of these complexes show that the X-Cu moiety (X=Cl, OTf, C F ) lies opposite the bridging hydrogen atom of the diborane and is near perpendicular to the B-B bond, interacting almost equally with both boron atoms and causing a B-B bond elongation. DFT studies show that σ donation from and π backdonation to the pseudo-π-like B-B bond account for their formation. Astoundingly, these copper σ complexes are inert to ligand exchange with pyridine under either heating or photoirradiation.

Dihalodiboranes(4) react with a N-heterocyclic silylene (NHSi) to generate NHSi adducts of 1-aryl-2-silyl-1,2-diboraindanes, as was confirmed by X-ray crystallography, featuring the functionalization of both B-X (X=halogen) bonds and a sp - or sp -C-H bond under mild conditions. Coordination of a third NHSi to the proposed 1,1-diaryl-2,2-disilyldiborane(4) intermediates, generated by a twofold B-X insertion, may be crucial for the C-H borylation that leads to the final products. Notably, our results demonstrate the first C-H borylation with a strong B-F bond activated by silylene insertion.

The γ-nitrogen insertion of arylazides into the B–B bond of electron-rich cyclic μ-hydridodiboranes yields unsymmetrical polyheterocyclic 1,1-diboryltriazenes, which may undergo further NHC ring expansion/fusion and thermally induced loss of N2.

The combination of electron-rich diaminoalkynes and ditopic Lewis acids diboranes(4) leads to unusual uncatalysed diboration reactions involving internal Lewis adduct, zwitterion, and C-C bond formation. The products are novel multicyclic, charge-separated compounds with intramolecular dative bonds.

The reactions of terminal acetylenes with doubly Lewis base-stabilised diborenes resulted in different outcomes depending on the nature of the ligands at boron and the conformation of the diborene (cyclic...

The reaction of the tetrahalodiboranes(4) BF, BCl, and BBr with a Lewis basic platinum(0) complex led to the isolation of the cis-bis(difluoroboryl) complex cis-[(CyP)Pt(BF)] (1) and the novel borylborato complexes trans-[(CyP)Pt{B(X)-BX}] (2, X = Cl; 3, X = Br), respectively. The trans influence of the borylborato group was found to be one of the strongest ever observed experimentally. Furthermore, the reactivity of little-explored diaryldifluorodiboranes(4) FB-BMes and the new derivative FB-BAn (An = 9-anthryl) toward a range of platinum(0) complexes was investigated. Reactions with relatively nonbulky platinum(0) complexes led to the formation of unsymmetrical cis-bis(boryl) complexes cis-[(RP)Pt(BF)(BMes)] (6, R = Me; 7, R = Et) as well as the first example of a fourfold-unsymmetrical bis(boryl) complex, [(MeP)(CyP)Pt(BF)(BMes)] (12). The use of a more bulky Pt complex provided access to the unprecedented dinuclear bis(boryl) complexes [{( iPrP)Pt}(μ-BF)(μ-BAr)] (8, Ar = Mes; 9, Ar = An), which feature two different μ-bridging boryl ligands.

The transfer hydrogenation of N-heterocyclic carbene (NHC)-supported diborenes with dimethylamine borane proceeds with high selectivity for the trans-1,2-dihydrodiboranes.D FT calculations,s upported by kinetic studies and deuteration experiments,s uggest as tepwise proton-first-hydride-second reaction mechanism via an intermediate m-hydrodiboronium dimethylaminoboratei on pair.Since the 1925 landmark discovery by Meerwein and Verley of the aluminum alkoxide-promoted hydrogenation of ketones using alcohols as sacrificial hydrogen donors, [1] transfer hydrogenation has become an attractively mild and selective alternative to direct hydrogenation. [2] Being easy-tohandle hydrogen-storage materials, [3] ammonia borane (AB = H 3 N·BH 3 )a nd amine boranes (R 2 NH·BH 3 )h ave also demonstrated their usefulness in catalytic transfer hydrogenation reactions. [4] While the majority of these reactions are applied to polar substrates,s uch as imines and ketones, [5] there are several examples of transition-metal-and main-group-catalyzed transfer hydrogenations of apolar N=N, [6] C=C, [7] and CC bonds [8] using AB or dimethylamine borane (DMAB) as the hydrogen source.S pontaneous,u ncatalyzed transfer hydrogenation reactions with AB or DMAB have only been reported for imines, [9] highly polarized olefins, [10] aminoboranes [11] and, most recently,i minoboranes. [12] Detailed experimental and theoretical studies have shown that, in the case of imines and iminoboranes,t he reaction proceeds via pre-coordination of the protic amine hydrogen to the more electronegative nitrogen atom, followed by concerted delivery of both the protic and hydridic hydrogen atoms to the unsaturated bond, via the six-membered transition state depicted in Figure 1a. [9,12] In contrast, the Angewandte Chemie Communications 9783