cg050172d_si_002.cif (15.54 kB)

Strong and Weak Hydrogen-Bonding Interactions in the Structures of N,N‘,N‘ ‘-Trisubstituted Guanidinium Chlorides and Bromides

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posted on 07.09.2005, 00:00 by Farouq F. Said, Tiow-Gan Ong, Glenn P. A. Yap, Darrin Richeson
The reaction of two trisubstituted guanidines N,N‘,N‘ ‘- triisopropylguanidine (TPG) and N,N-diisopropyl-N‘ ‘-2,6-dimethylphenylguanidine (DPArG) with HX or equivalents (X = Cl, Br) yielded the anticipated guanidinium halide salts. The structures of TPGH+X- (X = Cl, 1), TPGH+X-·H2O (X = Br, 3·H2O), and DPArGH+X- (X = Cl, 2; Br, 4) were determined by single-crystal X-ray diffraction analysis to examine the potential intermolecular interactions in these compounds and their influence on the extended structures that were observed. The formation of strong, charge-assisted hydrogen bonds, NH+···X-, dominates the extended structures. In addition, weaker interactions between the N-substituents and between the X- anions and CH bonds of the substituents have an apparent role in the structures of these materials. While the TPGH+ cation displayed a C3 propeller-type orientation in the structures of 1 and 3·H2O, two different isomeric forms for the less symmetric DPArGH+ cations were observed, and the identity of the anion and of the substituents both appear to be important in determining which form is obtained. Although the DPArGH+ cation exhibited different isomeric structures in 2 and 4, a common structural motif consisting of hydrogen-bonded chains was observed in their solid-state structures.