inary Group 15 Polyazides. Structural Characterization of [Bi(N3)4]−, [Bi(N3)5]2–, [bipy·Bi(N3)5]2–, [Bi(N3)6]3–, bipy·As(N3)3, bipy·Sb(N3)3, and [(bipy)2·Bi(N3)3]2 and on the Lone Pair Activation of Valence Electrons
Journal article, 2012

The binary group 15 polyazides As(N3)3, Sb(N3)3, and Bi(N3)3 were stabilized by either anion or donor−acceptor adduct formation. Crystal structures are reported for [Bi(N3)4]–, [Bi(N3)5]2–, [bipy·Bi(N3)5]2–, [Bi(N3)6]3–, bipy·As(N3)3, bipy·Sb(N3)3, and [(bipy)2·Bi(N3)3]2. The lone valence electron pair on the central atom of these pnictogen(+III) compounds can be either sterically active or inactive. The [Bi(N3)5]2– anion possesses a sterically active lone pair and a monomeric pseudo-octahedral structure with a coordination number of 6, whereas its 2,2′-bipyridine adduct exhibits a pseudo-monocapped trigonal prismatic structure with CN 7 and a sterically inactive lone pair. Because of the high oxidizing power of Bi(+V), reactions aimed at Bi(N3)5 and [Bi(N3)6]– resulted in the reduction to bismuth(+III) compounds by [N3]–. The powder X-ray diffraction pattern of Bi(N3)3 was recorded at 298 K and is distinct from that calculated for Sb(N3)3 from its single-crystal data at 223 K. The [(bipy)2·Bi(N3)3]2 adduct is dimeric and derived from two BiN8 square antiprisms sharing an edge consisting of two μ1,1-bridging N3 ligands and with bismuth having CN 8 and a sterically inactive lone pair. The novel bipy·As(N3)3 and bipy·Sb(N3)3 adducts are monomeric and isostructural and contain a sterically active lone pair on their central atom and a CN of 6. A systematic quantum chemical analysis of the structures of these polyazides suggests that the M06-2X density functional is well suited for the prediction of the steric activity of lone pairs in main-group chemistry. Furthermore, it was found that the solid-state structures can strongly differ from those of the free gas-phase species or those in solutions and that lone pairs that are sterically inactive in a chemical surrounding can become activated in the free isolated species.

energetic materials


vibrational spectroscopy

density functional theory


Ralf Haiges

David A. Dixon

Edward B. Garner

Karl O. Christe

Inorganic Chemistry

0020-1669 (ISSN) 1520-510X (eISSN)

Vol. 51 2 1127-1141

Subject Categories

Inorganic Chemistry

Theoretical Chemistry



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