HYDROGEN-BONDING .58. INFRARED STUDY OF THE DECAMETHONIUM HALIDE DIHYDRATES, IDENTIFICATION OF AN UNEQUIVOCAL C-2H(H2O.I-)2 CLUSTER, AND AN OVERVIEW OF QUATERNARY AMMONIUM HALIDE MONOHYDRATE STRUCTURE

We have determined the infrared spectra of the dihydrates of decamethonium iodide. bromide, chloride, and fluoride. Comparison with compounds of known structure demonstrates that all four dihydrates, which are halide ion monohydrates, contain planar C2h (H2O.X-)2 monohydrate clusters. This is the first clear and unequivocal evidence we have obtained for a C2h (H2O.I-)2 Cluster. The fluoride also forms a single higher hydrate with 4.5 H2O; the iodide, bromide, and chloride do not form higher hydrates. It is likely, by analogy with hexamethonium halides, that these latter three halides form monohydrates (halide ion hemihydrates); however, this possibility was not investigated. Trends in the nature of halide monohydrate structure are summarized for a number of quaternary ammonium halides that we have investigated.