Lewis-Base Adducts of Main Group 1 Metal Compounds. VI. Novel Hydrogen Bonding and a Novel Binuclear Aquated Lithium Cation in [(H₂O)₂Li(OH₂)₂Li(OH₂)₂]²⁺.2Cl^-.6L (L = 2,6-Dimethylpyridine)

Abstract

The title compound, isolated as an artefact of the recrystallization of lithium chloride from 2,6-dimethylpyridine, and the subject of a single-crystal X-ray study (R = 0.063 for 1200 'observed' reflections), contains the novel centrosymmetric [(H₂O)₂Li(OH₂)₂Li(OH₂)₂]²⁺ cation. Li- O(bridging) are 2.05(2), 2.00(2)Ǻ; Li-O (terminal) are 1.88(2), 1.88(2)Ǻ. Li-O-Li is 89.1(7) and O-Li-O′ (core) is 90.9(8)°. The angle between the terminal water oxygens at the lithium is 122.6(11)° and O(terminal)-Li-O(bridge) range from 101.7(7) to 123.0(10)°. An elegant hydrogen bonding scheme is found, one hydrogen atom from each of the water molecules being associated with the chloride counterion at 2.0- 2.2 Ǻ; the other hydrogen atom of each water is directed towards the nitrogen atom of one of each of the base molecules, H…N ~ 1.6-2.1 Ǻ.