Cationic Pb₂ Dumbbells Stabilized in the Highly Covalent Lead Nitridosilicate Pb₂Si₅N₈

Abstract

Due to the weak oxidative force of N2, nitrides are only typically formed with the less electronegative metals. Meeting this challenge, we here present Pb2Si5N8, the first nitridosilicate containing highly electron‐affine cations of a metal from the right side of the Zintl border. By using advanced synchrotron X‐ray diffraction, the crystal structure was determined from a tiny single crystal of 1×3×3 μm3 in size, revealing a significantly different bonding situation compared to all other nitridosilicates known so far. Indeed, DFT calculations confirm distinct amounts of covalency not only between Pb and N but also between formal Pb2+ cations. Thus, unprecedented cationic Pb2 dumbbells with a stretching vibration at 117 cm−1 were found in Pb2Si5N8, the first representative of a crystallographically elucidated lead nitride, stabilized by high amounts of covalency.

Exploring Main Group Metal Borosulfates: Similarities and Differences of Two New Borosulfates M[B2O(SO4)3] (M = Sr, Pb)

“…in the closely related compound class of borophosphates isotypic compounds were found for M [BO(PO 4 )] with M = Sr, Ba and Pb . However, in nitridosilicates, the crystal structures of Sr 2 Si 5 N 8 and Pb 2 Si 5 N 8 are only isopointal, due to the formation of Pb 2 dumbbells. Furthermore, lone pair activity of s 2 ‐ions might influence the surrounding framework like in recently reported SnB 2 O 3 F 2 , where unique layers of condensed BO 3 F‐tetrahedra yield an excellent non‐linear optical SHG effect …”

Post‐Synthetic Modification: Systematic Study on a Simple Access to Nitridophosphates

“…Considering possible driving forces of the presented approach, the targeted formation of the more stable halides and Coulomb's law certainly have a major influence. Similar explanations are given for metathesis reactions or a corresponding ion exchange in nitridosilicates [21–24, 37] . Furthermore, a possible reduction in volume can be considered as driving force, as MP and HP/HT conditions were applied.…”

“…Similar explanations are given for metathesis reactions or a corresponding ion exchange in nitridosilicates. [21][22][23][24]37] Furthermore, a possible reduction in volume can be considered as driving force, as MP and HP/HT conditions were applied. However, more precise conclusions about this assumption cannot be drawn, since structural information on all starting materials and products under the experimental reaction conditions would be necessary.…”

Post‐Synthetic Modification: Systematic Study on a Simple Access to Nitridophosphates

“…Such topotactic ion‐exchange reactions on nitridophosphates have so far only been reported for the synthesis of sodalite‐like Zn 7 [P 12 N 24 ]Cl 2 by deprotonating Zn 5 H 4 [P 12 N 24 ]Cl 2 with ZnCl 2 [6, 20] . Moreover, post‐synthetic modification by ion exchange has generally been investigated very sparsely on nitride substance classes, although the huge potential of this approach has been demonstrated for related nitridosilicates [21–24] …”

“…Such topotactic ion-exchange reactions on nitridophosphates have so far only been reported for the synthesis of sodalite-like Zn 7 [6,20] Moreover, post-synthetic modification by ion exchange has generally been investigated very sparsely on nitride substance classes, although the huge potential of this approach has been demonstrated for related nitridosilicates. [21][22][23][24] In this contribution we present the first systematic study on the post-synthetic modification of nitridophosphates by ion exchange reactions. But, as preliminary tests have shown, that an analogous approach as used for (nitrido-)silicates cannot be easily transferred to nitridophosphates ( Figure S1-S3), we combine ion exchange reactions/salt metathesis with HP/HT and MP methods within this work.…”