Azolylborane adducts. Structural and conformation analysis by X-ray diffraction and NMR. Protic-hydric (C-H^δ+-^δ-H-B) and protic-fluoride (C-H^δ+-^δ-F-B) interactions

The preparation, NMR and X-ray diffraction studies of a series of azolylboron hydrides derived from pyrrole, indoie, and carbazole coordinated with tetrahydrofuran, pyridine, and imidazoie are reported. The azolyl substituents are very electroattractive leading to an acidic boron atom which strongly coordinates with the Lewis bases. The stabilization of the -BH₂- groups against disproportionation could be explained in terms of the interactions found between the acidic hydrogen atoms of the heterocycles (C-H^δ+ acceptor) and the hydrides (B-H^δ- donors).