Abstract
We present here three compounds consisting of pyridinium or morpholinium hydrogen oxalates, each displaying different hydrogen-bonding motifs, resulting in chains for 4-(di-methyl-amino)-pyridinium hydrogen oxalate 0.22-hydrate, C7H11N2 +·C2HO4 -·0.22H2O (1), dimers for 4-tert-butyl-pyridinium hydrogen oxalate, C9H14N+·C2HO4 - (2), and chains for morpholin-ium hydrogen oxalate, C4H10NO+·C2HO4 - (3).
Highlights
We present here three compounds consisting of pyridinium or morpholinium hydrogen oxalates, each displaying different hydrogen-bonding motifs, resulting in chains for 4-(dimethylamino)pyridinium hydrogen oxalate 0.22-hydrate, C7H11N2+ÁC2HO4ÀÁ0.22H2O (1), dimers for 4-tert-butylpyridinium hydrogen oxalate, C9H14N+ÁC2HO4À (2), and chains for morpholinium hydrogen oxalate, C4H10NO+ÁC2HO4À (3)
Oxalate is a common ligand in coordination chemistry, utilized for its ability to chelate and bridge metal ions to form complexes and coordination polymers (Decurtins, 1999)
Oxalate has the unusual property of containing a C—C bond with a bond order of slightly less than one, resulting in the carboxylate moieties taking a perpendicular orientation in gas phase calculations (Herbert & Ortiz, 2000)
Summary
Oxalate is a common ligand in coordination chemistry, utilized for its ability to chelate and bridge metal ions to form complexes and coordination polymers (Decurtins, 1999). Oxalate has the unusual property of containing a C—C bond with a bond order of slightly less than one, resulting in the carboxylate moieties taking a perpendicular orientation in gas phase calculations (Herbert & Ortiz, 2000). While this structure is the most energetically favourable, the difference in energy between the 90 and 0 torsion angles is slight and is often overridden in hydrogen-bonded structures. Our research group has an interest in these precursors as part of our investigations into molecular magnets (Keene, et al 2010), for their usefulness in this role, but for the complex hydrogen-bonded structures that often arise on crystallization. Previous work from our group has focused on the structure of discrete oxalate dianions and drawn correlations between torsion angles, bond lengths and the crystal packing (Keene et al, 2012)
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