9-Borafluorenes – NMR spectroscopy and DFT calculations. Molecular structure of 1,2-(2,2′-diphenylylene)-1,2-diethyldiborane

Abstract

9-Borafluorene derivatives 1 (9-R = Et (a), Ph (b), Cl (c), NEt2 (d)), the pyridine adduct 1py+ and 1,2-(2,2′-biphenylylene)-1,2-diethyldiborane(6) (3), were studied by 11B and 13C NMR spectroscopy to obtain a fairly complete data set for the first time. The molecular structure of the doubly hydrogen-bridged 1,2-diphenylenediborane 3 was determined by X-ray diffraction. The gas-phase structures of the compounds 1, related derivatives, and of some doubly hydrogen-bridged 1,2-diphenylenediboranes were optimized by quantum chemical calculations (B3LYP/6-311+G(d,p) level of theory) and NMR parameters, such as chemical shifts, 11B chemical shift tensors and indirect nuclear 13C–11B spin–spin coupling constants were calculated at the same level of theory and compared with experimental data.