PUB - Publikationen an der Universität Bielefeld

The oxidation potentials E-ox of a series of 2,3-dihydro-1H-1,3,2-diazaboroles (BuNCH)-Bu-t=CHN(Bu-t)BR (1a-i) and of the corresponding saturated 1,3,2-diazaborolidines 2a (R = NH2)2b (OMe), 2c (Me), 2d (NMe2), 2e (H), 2f (SMe), 2g (SnMe3) 2h (Br), 2i (CN) were determined by cyclovoltammetry in CH2Cl2 solution. The potentials E-ox of the irreversible electrochemical oxidations range from E-ox = -288 mV (1a) to 752 mV (1i). In contrast to this, E-ox of the corresponding diazaborolidines are anodically shifted by 260 mV (1d, 2d) to 752 mV (1b, 2b) and vary from 280 mV (2a) to 1164 mV (2i). Gas-phase photoelectron spectra of representatives of both series of compounds were recorded and assessed by density functional calculations. The first ionization potentials of the 2,3-dihydro-1H-1,3,2-diazaboroles range in the series 1c (7.1 eV) < If (7.3 eV) < 1e = 1h (7.4 eV) < 1i (7.7 eV). They differ by less than 0.3 eV from the first ionization potentials determined for the saturated analogues [1st IP for 2c (7.3 eV) < 2e = 2f (7.4 eV) < 2h (7.7 eV)].