10.1021/jacs.5b08033.s002 Huizhen Li Huizhen Li Nana Ma Nana Ma Wenjuan Meng Wenjuan Meng Judith Gallucci Judith Gallucci Yongqing Qiu Yongqing Qiu Shujun Li Shujun Li Qianyi Zhao Qianyi Zhao Jie Zhang Jie Zhang Ji-Cheng Zhao Ji-Cheng Zhao Xuenian Chen Xuenian Chen Formation Mechanisms, Structure, Solution Behavior, and Reactivity of Aminodiborane American Chemical Society 2015 form sodium aminodiboronate ion pair reversibly THF room temperature exchange NH 2BH AoB 2 H NMR MS B 2H DB ion pair AB crystal analysis NH 3BH AaDB NH 2B ADB 2015-09-30 00:00:00 Dataset https://acs.figshare.com/articles/dataset/Formation_Mechanisms_Structure_Solution_Behavior_and_Reactivity_of_Aminodiborane/2127382 A facile synthesis of cyclic aminodiborane (NH<sub>2</sub>B<sub>2</sub>H<sub>5</sub>, ADB) from ammonia borane (NH<sub>3</sub>·BH<sub>3</sub>, AB) and THF·BH<sub>3</sub> has made it possible to determine its important characteristics. Ammonia diborane (NH<sub>3</sub>BH<sub>2</sub>(μ-H)­BH<sub>3</sub>, AaDB) and aminoborane (NH<sub>2</sub>BH<sub>2</sub>, AoB) were identified as key intermediates in the formation of ADB. Elimination of molecular hydrogen occurred from an ion pair, [H<sub>2</sub>B­(NH<sub>3</sub>) (THF)]<sup>+</sup>[BH<sub>4</sub>]<sup>−</sup>. Protic-hydridic hydrogen scrambling was proved on the basis of analysis of the molecular hydrogen products, ADB and other reagents through <sup>2</sup>H NMR and MS, and it was proposed that the scrambling occurred as the ion pair reversibly formed a BH<sub>5</sub>-like intermediate, [(THF)­BH<sub>2</sub>NH<sub>2</sub>]­(η<sup>2</sup>-H<sub>2</sub>)­BH<sub>3</sub>. Loss of molecular hydrogen from the ion pair led to the formation of AoB, most of which was trapped by BH<sub>3</sub> to form ADB with a small amount oligomerizing to (NH<sub>2</sub>BH<sub>2</sub>)<sub><i>n</i></sub>. Theoretical calculations showed the thermodynamic feasibility of the proposed intermediates and the activation processes. The structure of the ADB·THF complex was found from X-ray single crystal analysis to be a three-dimensional array of zigzag chains of ADB and THF, maintained by hydrogen and dihydrogen bonding. Room temperature exchange of terminal and bridge hydrogens in ADB was observed in THF solution, while such exchange was not observed in diethyl ether or toluene. Both experimental and theoretical results confirm that the B–H–B bridge in ADB is stronger than that in diborane (B<sub>2</sub>H<sub>6</sub>, DB). The B–H–B bridge is opened when ADB and NaH react to form sodium aminodiboronate, Na­[NH<sub>2</sub>(BH<sub>3</sub>)<sub>2</sub>]. The structure of the sodium salt as its 18-crown-6 ether adduct was determined by X-ray single crystal analysis.