The reaction of Aryl–N=CH–CH=N–Aryl (3a: Aryl = 2,6‐Me2C6H3; 3b: Aryl = 2,4,6‐Me3C6H2) with 2 equiv. BCl3 in a toluene/hexane mixture at –50 °C led to an inseparable mixture of borolium salts [Aryl–Na=CH–CH=N(Aryl)BCl2(Na–B)]+BCl4– (4a: Aryl = 2,6‐Me2C6H3; 9a: Aryl = 2,4,6‐Me3C6H2) and [Aryl–Na=CH–C(Cl)=N(Aryl)BCl2(Na–B)]+BCl4– (4b: Aryl = 2,6‐Me2C6H3; 9b: Aryl = 2,4,6‐Me3C6H2) and the bicyclic species [HCa=N(Aryl)BCl2N(Aryl)–Cb=(Ca–Cb)]2 (5: Aryl = 2,6‐Me2C6H3; 10: Aryl = 2,4,6‐Me3C6H2). Sodium amalgam reduction of borolium salts 4a,b and 9a,b afforded inseparable mixtures of the diazaboroles 2,6‐Me2C6H3NaCH=CR–Nb(2,6‐Me2C6H3)BCl(Na–B) (1: R = H; 6: R = Cl) and 2,4,6‐Me3C6H2NaCH=CR–Nb(2,4,6‐Me3C6H2)BCl(Na–B) (2: R = H; 11: R = Cl). In order to obtain pure 1 and 2, diazabutadienes 3a and 3b were slowly combined with 2 equiv. BCl3 in the same solvents at –78 °C. The acyclic adducts Cl3BN(Aryl)=CH–CH=N(Aryl)BCl3 (7a: Aryl = 2,6‐Me2C6H3; 7b: Aryl = 2,4,6‐Me3C6H2) were reduced with sodium amalgam to furnish the aminoboranes Cl2BN(Aryl)CH=CH–N(Aryl)BCl2 (8: Aryl = 2,6‐Me2C6H3; 12: Aryl = 2,4,6‐Me3C6H2). Stirring solutions of 8 and 12 in the presence of CaH2 cleanly gave the diazaboroles 1 and 2, respectively. The novel compounds were characterized by elemental analyses and 1H‐, 11B‐, 13C NMR and mass spectra. The molecular structures of 1, 4a, 5 and 8 were elucidated by single X‐ray diffraction analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The reaction of the aminohaloboranes (Me 2 N)(R)BX (1) (a: R = Ph, X = Cl; b: R = Me, X = Br; c: R = iPr, X = Cl) with the di-Grignard reagent (BrMg) 2 CH 2 in ethyl ether/benzene mixtures afforded the diborylmethanes [(Me 2 N)(R)B] 2 CH 2 (2) (a: R = Ph; b: R = Me; c: R = iPr), which were subsequently converted into the corresponding bis(chloroboryl)methanes [(Cl)(R)B] 2 CH 2 (3) (a: R = Ph; b: R = Me; c: R = iPr). Base-assisted cyclocondensation of 3a-c with 1,2-diisopropylhydrazine afforded 1,2-diisopropyl-1,2-diaza-3,5-diorgano-3,5-diborolidines (4) (a: R = Ph; b: R = Me; c: R = iPr). Derivative 4a was deprotonated by potassium bis(trimethylsilyl)amide to give (1,2diisopropyl-1,2-diaza-3,5-diphenyl-3,5-diborolidinyl)potassium (5).