Crystal and molecular structure of a complex formed between the hydrochloride of 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene and 5,5 '-dibromo-2,2 '-biphenol

A complex of 5,5 ' -dibromo-2,2 ' -biphenol with 7-methyl-1,5,7-triazabicyc lo[4.4.0]dec-5-ene (MTBD) hydrochloride has been studied using X-ray diffra ction, FT-IR, and H-1 NMR spectroscopy. The compound crystallises in the sp ace group P2(1)/c with a = 9.738(2), b = 12.100(2), c = 18.347(4) Angstrom, beta = 92.62(3)degrees (at 100 K), and Z = 4. In the crystal structure, th e MTBDH+ cation, a chloride anion, and one molecule of 5,5 ' -dibromo-2,2 ' -biphenol are present. In the solid state the Cl- anion is an acceptor in N--H...Cl-, O-H...Cl- and C-H...Cl- intermolecular hydrogen bonds. In chloroform the structure of the complex is comparable with that in the s olid, whereas in acetonitryle the complex assumes a new structure owing to the almost complete dissociation of the protonated MTBD molecule. The 5,5 ' -dibromo-2,2 ' -biphenol molecule is hydrogen-bonded with the chloride ani on. Within this complex the OH...OH hydrogen bond shows very large proton p olarisability indicated by the continuous absorption in the FTIR spectrum. (C) 2001 Elsevier Science B.V. All rights reserved.