Stacking variants of MnP4: preparation and structure of 6-MnP4

Abstract

Two new polymorphs of MnP 4 were prepared by reaction of the elemental components in a tin flux or by chemical transport in the presence of iodine. They can be considered as stacking variants (2-MnP4 and 6-MnP4) of a previously reported modification of this composition which is now called 8-MnP 4. The structure of 6-MnP 4 was determined from sin_gle-crystal counter data. It is triclinic, space group P1, with a = 16.347 (3) The Mn atoms with formal oxidation number +2 (d 5 system) are displaced from the centers of their octahedra to form pairs with Mn-Mn bonding distances of 2.92 and 2.96 A. In agreement with a simple bonding description based on classical two-electron bonds, 6-MnP 4 is diamagnetic and semiconducting. As is the case for all transition-metal tetraphosphides the P atoms form a two-dimensionally infinite net of condensed, ten-membered rings. A puckered net of pentagons and hexagons formed by transition-metal and P atoms can be considered as the basic building element of the structures of CrP 4, 2-, 6-, 8-MnP 4, and fl-FeP 4. The different stacking possibilities of this net are described in a systematic way.

The Metal Flux: A Preparative Tool for the Exploration of Intermetallic Compounds

“…Similarly, powders of the binary alloys were used for the preparation of the ternary polyphosphides VNi 4 P 16 , NbNi 4 P 16 , and WNi 4 P 16 140. Three stacking variants of the binary manganese polyphosphide MnP 4 are known: 2‐MnP 4 ,56 6‐MnP 4 ,50 and 8‐MnP 4 49. The missing stacking variant 4‐MnP 4 could only be prepared in form of a solid solution with chromium: Cr 1− x Mn x P 4 with x having values between 0.3 and 0.7.…”

“…Examples for binary phosphides and polyphosphides prepared in liquid tin are given in Table 1. It should be mentioned that the compounds SiP (sphalerite type),47 p ‐SiP 2 (pyrite type),47 CrP 4 ,48 MoP 4 ,48 and one modification of MnP 4 49—subsequently called 8‐MnP 4 50—were first thought to be high‐pressure compounds, because they could not be obtained by direct reaction of the elemental components at normal pressure. Their preparation by using a tin flux (for references see Table 1) showed that they must be considered as ambient‐pressure compounds.…”

Metallische Schmelzen – Reaktionsmedien zur Präparation intermetallischer Verbindungen

“…Beispiele für binäre Phosphide und Polyphosphide, die aus Zinnschmelzen erhalten wurden, sind in Tabelle 1 angeführt. Es sollte erwähnt werden, dass die Verbindungen SiP (Sphalerit‐Typ),47 p ‐SiP 2 (Pyrit‐Typ),47 CrP 4 ,48 MoP 4 48 und eine Modifikation von MnP 4 49 – später 8‐MnP 4 genannt50 – ursprünglich als Hochdruckphasen beschrieben wurden, weil sie durch direkte Reaktion bei normalem Druck nicht erhalten werden konnten. Mit ihrer Herstellung aus einer Zinnflux (Literaturangaben in Tabelle 1) wurde bewiesen, dass es sich nicht um Hochdruckverbindungen handelt.…”

Peierls‐Distorted Monoclinic MnB4with a MnMn Bond

“…There are two metalmetal distances observed in MnB 4 , 269.61 (7) pm and 320.33 (7) pm (Figure 3 C), which is in contrast to the equally spaced metal atoms in CrB 4 . Compared to diamagnetic MnP 4 , which has an oxidation state of Mn II , MnB 4 shows even shorter Mn-Mn distances (in MnP 4 , Mn-Mn distances are greater than 292.1 pm [18] ). The MnÀMn bond in [Mn 2 (CO) 10 ] is also longer (292.3 pm) than the one observed in MnB 4 .…”