Sodium Tetraazidoaurate(III)-From Na[AuCl4]·2H2O to Na[Au(N3)4] and Beyond One Step at a Time.

The novel sodium tetrachlorido-/azidoaurate(III) dihydrates Na[AuCl4- x(N3)x]·2H2O (x = 0, 1, 2, 3, 4) provide the first example of a complete series of gradual substitution on square planar complex anions to be described. Transparent yellow to dark orange single crystals of these phases were synthesized by reaction of NaN3 and AuCl3 or HAuCl4 in different molar ratios from aqueous solution. Controlled dehydration of Na[Au(N3)4]·2H2O led to Na[Au(N3)4]·H2O and Na[Au(N3)4] in form of orange microcrystalline powders, the latter being a highly explosive material. Predominant structural features of all phases are discrete anions [AuCl4- x(N3)x]- with gold in an ordered square planar coordination of azide/chloride anions. Vibrational spectra show good agreement with other known azidoaurates(III).