Metal‐like Ductility in Organic Plastic Crystals: Role of Molecular Shape and Dihydrogen Bonding Interactions in Aminoboranes

Ductility is a common phenomenon in many metals but is difficult to achieve in molecular crystals. Organic crystals bend plastically on one or two face‐specific directions but fracture when stressed in any other arbitrary directions. An exceptional metal‐like ductility and malleability in the isomorphous crystals of two globular molecules, BH₃NMe₃ and BF₃NMe₃, is reported, with characteristic tensile stretching, compression, twisting, and thinning. The mechanically deformed samples, which transition to lower symmetry phases, retain good long‐range order amenable to structure determination by single‐crystal X‐ray diffraction. Molecules in these high‐symmetry crystals interact through electrostatic forces (B^??N⁺) to form columnar structures with multiple slip planes and weak dispersive forces between columns. On the other hand, the limited number of facile slip planes and strong dihydrogen bonding in BH₃NHMe₂ negates ductility. Our study has implications for the design of soft ferroelectrics, solid electrolytes, barocalorics, and soft robotics.     

Magnesium-Catalyzed Tandem Dehydrogenation-Dehydrocoupling: An Atom Economical Access to Alkynylboranes

Owing to the unusual reactivity of sterically hindered amine–borane complexes, a catalytic system based on magnesium salts was designed to perform a tandem dehydrogenation–dehydrocoupling between terminal alkynes and boranes. The reaction is providing pure alkynylboranes within few minutes at room temperature, with only two molecules of hydrogen as a byproduct.     

Borane Adducts of Hydrazoic Acid and Organic Azides: Intermediates for the Formation of Aminoboranes

The reaction of HN₃ with the strong Lewis acid B(C₆F₅)₃ led to the formation of a very labile HN₃?B(C₆F₅)₃ adduct, which decomposed to an aminoborane, H(C₆F₅)NB(C₆F₅)₂, above ?20 °C with release of molecular nitrogen and simultaneous migration of a C₆F₅ group from boron to the nitrogen atom. The intermediary formation of azide–borane adducts with B(C₆F₅)₃ was also demonstrated for a series of organic azides, RN₃ (R=Me₃Si, Ph, 3,5‐(CF₃)₂C₆H₃), which also underwent Staudinger‐like decomposition along with C₆F₅ group migration. In accord with experiment, computations revealed rather small barriers towards nitrogen release for these highly labile azide adducts for all organic substituents except R=Me₃Si (m.p. 120 °C, T_dec=189 °C). Hydrolysis of the aminoboranes provided C₆F₅‐substituted amines, HN(R)(C₆F₅), in good yields.     

Phosphoramidate‐Supported Cp*IrIII Aminoborane H2B=NR2 Complexes: Synthesis,Structure, and Solution Dynamics

Reaction of aminoboranes H₂B=NR₂ (R=iPr or Cy) with the cationic Cp*Ir^III phosphoramidate complex [IrCp*{κ²‐N,O‐Xyl(N)P(O)(OEt)₂}][BAr^F₄] generates the aminoborane complexes [IrCp*(H){κ¹‐N‐η²‐HB‐Xyl(N)P(OBHNR₂)(OEt)₂}][BAr^F₄] (R=iPr or Cy) in which coordination of a P=O bond with boron weakens the B=N multiple bond. For these complexes, solution‐ and solid‐state, as well as DFT computational techniques, have been employed to substantiate B?N bond rotation of the coordinated aminoborane.