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)2] (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)2Au(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)2Cu−NCAuCN]+ cations; short Au−Au bonds of 3.1405(2) A connect the anions. This bond is shorter than that observed in the analogous silver(I) structure, 2-Ag. The average M−C bond lengths of 1.984(8) A in 2-Au are significantly shorter than those found in 2-Ag, suggesting that Au(I) is smaller than Ag(I). Cu(dien)[Au(CN)2]2 (3, dien = diethylenetriamine) forms a 1-D chain of tetranuclear [Au(CN)2]- units...