Difference in bonding behaviour of azide and thiocyanate to Hg(II)-azoimidazoles

Mercury(II) acetate reacts with the 1-alkyl-2-(arylazo)imidazoles [RaaiR′ where R = H (a), Me (b); R′ = Me (1/3/5), Et (2/4/6)] and sodium azide in methanol solution to afford azido bridged polymeric complexes [Hg(RaaiR′)(N3)2]n (3/4). On setting up similar reaction condition, the reaction of Hg(OAc)2 with RaaiR′ and NH4SCN has yielded, instead of polymer, an ion-pair [Hg(RaaiR′)4][Hg(SCN)4] (5/6). The complexes are characterised by elemental analysis, IR, UV–Vis, 1H NMR spectral data and single-crystal X-ray structures of [Hg(HaaiEt)(μ-1,1-N3)2]n (4a) and [Hg(HaaiEt)4][Hg(SCN)4] (6a). The complex 4a is a coordination polymer with end-on (μ-1,1) azido bridge and 6a has tetrahedral structure.

Azide (N3-) and thiocyanate (SCN−) both are versatile bridging agents but bind differently with Hg(RaaiR′)-motif (RaaiR′ = 1-alkyl-2-(arylazo)imidazole). Azide gives 1D chain [Hg(RaaiR′)(μ-(1,3)-N3)2]n. Thiocyanate binds through S-centre and gives ion pair [Hg(RaaiR′)4][Hg(SCN)4].Figure optionsDownload as PowerPoint slide