2,2':6',2''-Terpyridine switches from tridentate to monodentate coordination in a gold(iii) terpy complex upon reaction with sodium azide.

Reaction of [AuCl(terpy-κ3-N1,1',1'')]Cl2 with an excess of sodium azide did not result in the expected exchange of the chlorido by an azido ligand to give [Au(N3)(terpy-κ3-N1,1',1'')]2+. Instead, X-ray structure analysis showed that the isolated product is [Au(N3)3(terpy-κ1-N1)], in which the terpyridine ligand is in a very rare monodentate coordination mode. This is also the dominant species in solution, together with a minor amount of [Au(N3)2(terpy-κ2-N1,1')]+. The stability of the tris(azido)gold(iii) moiety relative to other possible species was also confirmed by DFT calculations.