Chemische Verzwilligung von Salz und Metall in den Subnitridometallaten Ba₂₃Na₁₁(MN₄)₄ mit M=V, Nb, Ta

Abstract

Die Subnitridometallate Ba23Na11(MN4)4 (M=V, Nb, Ta) kristallisieren in einem neuen Strukturtyp, in dem sowohl ionische ortho‐Nitridometallat‐Anionen als auch Strukturmotive aus einfachen (inter)metallischen Packungen zu finden sind: Na‐zentrierte [Na8]‐Würfel als Ausschnitte aus der bcc‐Struktur von elementarem Natrium und Na‐zentrierte [Ba10Na2]‐Ikosaeder, wie sie z. B. in Laves‐Phasen vorkommen. Einkristall‐ und Pulverröntgenstrukturanalyse unterstreichen in Kombination mit quantenchemischen Berechnungen der elektronischen Struktur und Raman‐Spektroskopie den Charakter der Subnitridometallate als “chemische Zwillinge”. Sie weisen unabhängige Strukturbausteine mit lokal überwiegend entweder ionischer oder metallischer Bindung in einer insgesamt metallischen Verbindung auf.

Ba6(MN4)N2–x (M = MoVI/TaV), a Subvalent Nitridometalate with Perovskite‐like Crystal Structure

“…Ba 6 [(Mo 1– x Ta x )N 4 ]N 0.86 single crystals were yielded as main product in a synthesis targeted on the formation of the hypothetical subnitridomolybdate “Ba 23 Na 11 (MoN 4 ) 4 ”, analogous to the reported V, Nb, and Ta compounds . NaBa was the only byphase (see powder diffraction pattern in Figure S4, Supporting Information), in accordance with the reaction equation:…”

“…It has been shown that nitridometalate anions of V, Nb and Ta in formal oxidation states +V can occur in subvalent compounds, and it is within this context we present herein the first results for new subvalent compounds containing Mo(+VI). Furthermore, we show for the first time a ReO 3 ‐like connection pattern of [Ba 6 N] units.…”

“…Enlargement of the metallic fraction can be achieved by intercalating additional metal atoms between the internally ionic cluster units, as exemplified by the large number of alkali metal suboxides and alkaline earth metal subnitrides , . Examples for the enlargement of the ionic parts in subvalent structures have been given by alkali metal suboxometalates and alkaline earth metal subnitridometalates in which the monoatomar anions of suboxides and subnitrides formally are replaced by tetrahedral oxido‐ or nitridometalate anions [ M O 4 ] n – or [ M N 4 ] m – . However, all of them still comprise rather large metallic regions within their respective crystal structures and therefore show pronounced isotropic metallic behavior.…”