Syntheses and Structures of Lithium and Sodium Salt Complexes with Alkylpolyamine Ligands

Syntheses and single crystal X-ray structural characterizations are recorded for some complexes of lithium and sodium halides, MX, X = Cl, Br, I, with various alkylpolyamine ligands ‘lm(n)’ = [H2N(CH2)lNH(CH2)m(NH(CH2)n)NH2], lm(n) = 22, 222, 343, also 22′2″ = N((CH2)2NH2)3, and ‘apz’ = bis-1,4-(2-aminoethyl)piperazine, obtained by crystallization of the metal salt from solution in the neat base, or with the base in methanol solution. The complex LiCl : 22 (2:2) is a discrete dimer, the four-coordinate lithium atoms being bridged by the pair of polyamine ligands, with the chlorine atoms terminally bound. The complex LiBr : 22 (2:3) comprises a one-dimensional cationic polymer, four- and five-coordinate lithium atom types both being coordinated by discrete tridentate bases, and catenated by another, the anions remaining uncoordinated. A hydrolysis product LiBr : 22 : H2O (4:5:1) comprises a cationic web in two dimensions, the counterion remaining uncoordinated. The series of isomorphous complexes NaX : 222 (2:3), X = Br, I, are two-dimensional polymers, the sodium ions (on crystallographic 3-axes) being linked into a web normal to those axes by ligands which behave as chelates with pendant groups linking Na(en)3 (en = 1,2-ethane-diamine) type arrays, the counterions remaining uncoordinated. The adduct LiCl : apz (2:1), derivative of impurity in the 222 ligand, is also a two-dimensional web, the four-coordinate lithium atoms being linked by counterions in one dimension, and chelate-pendant-bridging ligands in the other. The complex LiI : 343 (1:1) is a one-dimensional helical polymeric cation, the four-coordinate lithium atoms being linked by bis(chelate)-bridging ligands with unbound counterions. The complexes of 22′2″ take two extreme forms, both manifested in LiCl : 22′2″ (2:2), wherein one set of crystallographically independent lithium atoms, disposed on crystallographic 3-axes, are linked by extended 22′2″ ligands centred about another set of such axes, (the counterions remaining unbound), into a two-dimensional web normal to the 3-axes of the crystal, the other set being bound by the other set of ligands as mononuclear tripod arrays, a motif found in other complexes where the counterion may or may not occupy a fifth coordination site. Here it does not, but in the complex LiBr : 22′2″ (2:2), we find both possibilities: [BrLi(22′2″)][Li(22′2″)]Br, the Li-Br distance in the neutral aggregate being 2.83(2) A, while in LiI : 22′2″ (1:1) we have the remarkable prospect of the lithium atoms of a pair of [Li(22′2″)]+ cations confronting each other along a crystallographic 3-axis (Li…Li 2.82(2) A), the counterions being disposed on another set of 3-axes between the cations. The adduct NaI : 22′2″ (1:1) is [INa(22′2″)], Na-I 3.101(2) A.