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The reactivity of a diruthenium tetrahydride complex towards three selected dihydroboranes was investigated. The use of [DurBH2] (Dur=2,3,5,6‐Me4C6H) and [(Me3Si)2NBH2] led to the formation of bridging borylene complexes of the form [(Cp*RuH)2BR] (Cp*=C5Me5; 1 a: R=Dur; 1 b: R=N(SiMe3)2) through oxidative addition of the B−H bonds with concomitant hydrogen liberation. Employing the more electron‐deficient dihydroborane [3,5‐(CF3)2‐C6H3BH2] led to the formation of an anionic complex bearing a tetraarylated chain of four boron atoms, namely Li(THF)4[(Cp*Ru)2B4H5(3,5‐(CF3)2C6H3)4] (4), through an unusual, incomplete threefold dehydrocoupling process. A comparative theoretical investigation of the bonding in a simplified model of 4 and the analogous complex nido‐[1,2(Cp*Ru)2(μ‐H)B4H9] (I) indicates that there appear to be no classical σ‐bonds between the boron atoms in complex I, whereas in the case of 4 the B4 chain better resembles a network of three B−B σ bonds, the central bond being significantly weaker than the other two. [ABSTRACT FROM AUTHOR]

A new pathway for the ring expansion reaction of antiaromatic boroles with organic azides is reported. While the reaction usually leads to 1,2‐azaborinines, it was diverted to the formation of a 1,2,3‐diazaborinine by changing the electronic characteristics of the reagents. The isolable azo‐azaborinine intermediate initially formed from the reaction of 1‐(2,3,4,5‐tetraphenylborolyl)ferrocene with 4‐azido‐N,N‐dimethylaniline gradually decomposed to a 1,2,3‐diazaborinine and benzonitrile. Both the spectroscopic properties and the reactivity of the heteroaromatic compound show analogies to pyridine, to which it is isoelectronic. Density functional theory (DFT) calculations provided insight into the mechanism of this unusual transformation. Nitrile & error: A new pathway for the ring expansion reaction of boroles with organic azides is presented, leading to a 1,2,3‐diazaborinine instead of the expected 1,2‐azaborinine. Mechanistic DFT calculations provided insight into the mechanism of formation of the BN2C3 heterocycle, and spectroscopic and reactivity studies demonstrated the analogies of the 1,2,3‐diazaborinine to pyridine. [ABSTRACT FROM AUTHOR]

A series of NHC-supported 1,2-dithienyldiborenes was synthesized from the corresponding (dihalo)thienylborane NHC precursors. NMR and UV/Vis spectroscopic data, as well as X-ray crystallographic analyses, were used to assess the electronic and steric influences on the B=B double bond of various NHCs and electron-donating substituents on the thienyl ligands. Crystallographic data showed that the degree of coplanarity of the diborene core and thienyl groups is highly dependent on the sterics of the substituents. Furthermore, any increase in the electron-donating ability of the substituents resulted in the destabilization of the HOMO and greater instability of the resulting diborenes. [ABSTRACT FROM AUTHOR]