Supramolecular C-H•••O, C-H•••N and C-H•••Cl interactions in metal compounds with multi-topic poly(pyrazolyl)borate ligands

Supramolecular C-H...O and C-H...N hydrogen bonding interactions in metal complexes with dihydrobis(1,2,4-triazolyl)borate (3), hydrotris(1,2,4-triazolyl)borate (4) and dihydrobis(tetrazolyl)borate ligands (5) have been analyzed statistically and with respect to their role in determining the crystal packing arrangement. The additional ring nitrogen atoms in these modified, multitopic poly(pyrazolyl)borate ligands are the origin of manifold C-H...O and C-H...N hydrogen bonds in this group of compounds. A recurrent example is the orientation of metal-coordinated triazolyl rings from 3 or 4 along the cisoid ligand(O/N)-metal-ligand(O/N) bonds because of C-H...O/N bonding. The additional nitrogen atoms play a dual role in enhancing the acidity of the ring hydrogen atoms and serving as hydrogen-bond acceptors. In polynuclear tris(triazolyl)borate copper structures with hydrated chloride anions or chloro ligands C-H...Cl contacts were observed. (C) 2003 Elsevier Science Ltd. All rights reserved.