The Syntheses and Structures of Ph4EN3 (E = P, As, Sb), an Example for the Transition from Ionic to Covalent Azides within the Same Main Group

The compounds Ph4EN3 (E = P, As, Sb) were prepared from the corresponding halides by ion exchange in aqueous solution. [Ph4P]N3 crystallizes in the triclinic space group $P{\bar 1}$, while [Ph4As]N3·H2O and Ph4SbN3 crystallize in the monoclinic space group P21/n. In contrast to ionic [Ph4P]+[N3]− and [Ph4As]+[N3]−, the antimony atom in Ph4SbN3 is pentacoordinated and contains a covalently bound azide ligand. This family of compounds serves as an example for the transition from ionic to covalent azides with increasing size of the central atom within the same group of the periodic table.