Iso-propyl-ammonium halidometallates. I. [Co ]· ( = Cl, Br), ZnCl , and [ZnCl ] salts.

An exploration of the iso-propyl-ammonium (IPA) metal halide structural space is conducted, initially, for cobalt(II) and zinc(II) halides as a counterpart to the more extensively studied metal halide systems containing the isomeric tri-methyl-ammonium cation. For cobalt(II) halides, the only compound obtained from slow evaporation of acidic aqueous solutions of iso-propyl-ammonium halide and cobalt(II) halide is (IPA)Co · ( = Cl, Br), namely, tris-(iso-propyl-ammonium) tetra-chlorido-cobaltate(II) chloride, (CHN)[CoCl]Cl, and tris-(iso-propyl-ammonium) tetra-bromido-cobaltate(II) bromide, (CHN)[CoBr]Br, regardless of the starting stoichiometric ratio of (IPA):Co . These structures consist of isolated tetra-hedral Co complexes and ions separated by IPA cations. One IPA cation hydrogen bonds to two complexes and to two halide ions to produce clusters. These clusters form stacks with hydrogen bonding from the remaining IPA cations linking the stacks into a tight, three-dimensional network. A 2:1 molar ratio of (IPA)Cl and ZnCl under similar growth conditions readily yields crystals of bis-(iso-propyl-ammonium) tetra-chlorido-zincate(II), (CHN)[ZnCl] or (IPA)ZnCl, consisting only of IPA cations and isolated ZnCl tetra-hedra. This despite the expectation of common structural chemistry for the similarly sized Co and Zn ions with 51 known isostructural ACoCl and AZnCl compounds out of 54 for the same monopositive A cation. Growth from a 1:1 ratio of (IPA)Cl:ZnCl yields crystals of poly[iso-propyl-ammonium [[di-chlorido-zincate(II)]-μ-chlorido]], {(CHN)[ZnCl]} or (IPA)ZnCl, in which parallel chains of corner-sharing ZnCl tetra-hedra are separated by IPA cations. This unusual zinc(II) halide chain structure has previously been observed only in [CH(CH)N]ZnCl salts ( = H, halogen). In contrast to these known compounds, which are found in polar ortho-rhom-bic space groups, the structure reported here is in ortho-rhom-bic .