1,2‐Diaza‐3,5‐diborolidine CH2BR1‐(NR2)2‐BR1: Potentielle Vorstufen zu cyclischen Diborylcarben‐Liganden

Abstract

AbstractThe reaction of the aminohaloboranes (Me2N)(R)BX (1) (a: R = Ph, X = Cl; b: R = Me, X = Br; c: R = iPr, X = Cl) with the di‐Grignard reagent (BrMg)2CH2 in ethyl ether/benzene mixtures afforded the diborylmethanes [(Me2N)(R)B]2CH2 (2) (a: R = Ph; b: R = Me; c: R = iPr), which were subsequently converted into the corresponding bis(chloroboryl)methanes [(Cl)(R)B]2CH2 (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 (1,2‐diisopropyl‐1,2‐diaza‐3,5‐diphenyl‐3,5‐diborolidinyl)potassium (5). Attempts to introduce a halogen atom to the carbon bridge between the two boron atom by treating 5 with either iodine or 1,2‐dibromoethane failed. Instead, bis(1,2‐diisopropyl‐1,2‐diaza‐3,5‐diphenyl‐3,5‐diborolidinyl) (C‐C) (6) was formed. In contrast to this, C‐silylation of the heterocycle to give 7 was effected by reaction of salt 5 with trimethylsilyl chloride. Similarly, treatment of HgCl2 with two molar equivalents of 5 gave rise to the formation of bis(1,2‐diisopropyl‐1,2‐diaza‐3,5‐diphenyl‐3,5‐diborolidinyl)mercury (8). The novel compounds were characterized by elemental analyses and various spectroscopic methods (1H‐, 11B{1H}‐, 13C{1H} NMR, MS). The molecular structures of 4a and 6–8 were elucidated by X‐ray diffraction analyses.