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organic compounds
In a series of six salts with organic nitrogen and phosphorus cations [2-methylpyridinium bis(pyrocatecholato-O,O′)borate, C6H8N+.C12H8BO4−, (1); 4-methylpyridinium bis(pyrocatecholato-O,O′)borate, C6H8N+.C12H8BO4−, (2) and (3) (two polymorphs); 1,10-phenanthrolinium bis(pyrocatecholato-O,O′)borate, C12H9N2+.C12H8BO4−, (4), and its dichloromethane solvate, C12H9N2+.C12H8BO4−.CH2Cl2, (5); and trimethylphosphonium bis(pyrocatecholato-O,O′)borate, C3H10P+.C12H8BO4−, (6)], the bis(catecholato)borate anion has approximate D2d (2m) symmetry, with the central spiro-B atom distorted from regular tetrahedral coordination geometry by reduction of the two intraring O—B—O bond angles. The two chelate rings show small deviations from planarity by folding about the OO axis. Ion pairs are formed by N—HO hydrogen bonding in all five salts with nitrogen-based cations, but there is no hydrogen bonding in the phosphonium salt; the hydrogen bonding leads to slight elongation of the B—O bond involved.