The versatility of lithium cation coordination modes in salts with [W(CN)(bpy)] anions

The synthesis and spectral and structural descriptions of two salts of formulas {[Li][Li(H 2 O)(μ-CN) 3 ]}[W(CN) 3 (bpy)] ( 1 ) and {Li}{[Li(μ-CN) 2 ][Li(μ-CN) 3 ]μ-Cl}[W(CN)(bpy)]·2H 2 O ( 2 ) were described. The structural investigation shows the influence of the size and charge of Li + on the nature of the CN − /Li + interaction and thus on the structure of the compounds. Both salts crystallize in the triclinic P 1&cmb.macr; space group with very similar cell parameters ( a , b and c differ by no more than 0.05 Å, α , β and γ less than 1°, and cell volume less than 4 Å 3 ) in spite of the different complex formulas. In 1 , two different lithium cations are observed. Only one compensates the anion charge, while the second one is tetrahedral and forms a complicated 1D network via three nitrogen atoms of cyano ligands trans to a bpy molecule. The molecular wires connect neighbouring molecules only by weak intermolecular interactions. In 2 , the 2D structure, with layers connected only by π-π stacking interactions, is observed. Lithium cations are involved in bonds with the nitrogen of cyano ligands. Effect of the cation size (compared to Cs + ) in Li 2 [W(CN) 6 (bpy)] salts on the nature of the interaction with cyanide ligands and on the crystal structure is discussed, unusual decrease of the W-W distance and increase of cell volume are observed.