Gold-gold interactions, as crystal engineering design elements in heterobimetallic coordination polymers

A series of coordination polymers containing Cu(II) and (Au(CN)(2)](-) units has been prepared. Most of their structures incorporate attractive gold-gold interactions, thus illustrating that such "aurophilic" interactions can be powerful tools for increasing structural dimensionality in supramolecular systems. [Cu(tren)Au(CN)(2)][Au(CN)(Z)] (1, tren tris(2-ethylamino)amine) forms a cation/anion pair, which is weakly linked by hydrogen bonds but not by aurophilic interactions. [Cu(en)(2)Au(CN)(2)][Au(CN)(2)] (2-Au, en = ethylenediamine) is a 2-D system composed of a chain of [Au(CN)(2)](-) anions and another chain of [(en)(2)Cu-NCAuCN](+) cations; short Au-Au bonds of 3.1405(2) Angstrom connect the anions. This bond is shorter than that observed in the analogous silver(1) structure, 2-Ag. The average M-C bond lengths of 1.984(8) Angstrom in 2-Au are significantly shorter than those found in 2-Ag, suggesting that Au(l) is smaller than Ag(I). Cu(dieu)[Au(CN)(2)](2) (3, then = diethylenetriamine) forms a 1-D chain of tetranuclear [Au(CN)(2)](-) units, that are bound to [Cu(dien)] centers. Aurophilic interactions of ca. 3.35 Angstrom hold the tetramer together. Cu(tmeda)[Au(CN)(2)](2) (4, tmeda = N,N,N',N'-tetramethylethylenediamine) forms a 3-D network by virtue of aurophilic interactions of 3.3450(10) and 3.5378(9) Angstrom. Altering the Cu:Au stoichiometry yields Cu(tmeda)-[Au(CN)(2)](1.5)(CIO4)(0.5),(5), which has an unusual 2-D rhombohedral layer structure (space group R32). Complex 5 is composed of three,which has an unusual 2-D rhombohedral layer structure (space group R32). Complex 5 is composed of three mutually interpenetrating Cu[Au(CN)(2)](1.5) networks which are interconnected by aurophilic interactions of 3.4018(7) and 3.5949(8) Angstrom. Weak antiferromagnetic coupling is observed in 2 and 5.