The First Alkaline-Earth Azidoaurate(III), Ba[Au(N 3 ) 4 ] 2  ⋅ 4 H 2 O.

Transparent, dark orange Ba[Au(N 3 ) 4 ] 2  ⋅ 4 H 2 O was synthesized by reaction of Ba(N 3 ) 2 and AuCl 3 or HAuCl 4 in aqueous solution. The novel barium tetraazidoaurate(III) tetrahydrate crystallizes in the monoclinic space group Cc (no. 9) with a=1813.68(17) pm, b=1737.95(11) pm, c=682.04(8) pm and β=108.849(4)°. The predominant structural features of Ba[Au(N 3 ) 4 ] 2  ⋅ 4 H 2 O are two crystallographically independent discrete anions [Au(N 3 ) 4 ] - with gold in a tetragonal planar coordination by nitrogen. Vibrational spectra show good agreement with those of other azidoaurates(III). Upon drying, this salt was shown to be a highly explosive material.