Darstellung und Kristallstruktur der Strontium‐ und Bariumpnictidoxide Sr 4 P 2 O, Sr 4 As 2 O, Ba 4 P 2 O und Ba 4 As 2 O

Sr 4 P 2 O (hellbraun), Sr 4 As 2 O (rotbraun), Ba 4 As 2 O (grauschwarz) und Ba 4 P 2 O (grauschwarz) wurden als mikrokristalline, hydrolyseempfindliche Pulver aus Metall, rotem Phosphor bzw. Arsen und Metalloxid im Molverhältnis 3 : 2 : 1 in Korundinnentiegeln in Quarzampullen unter Argon dargestellt (3 d 630°C, 2 d 1000°C, 2 d 1100°C). Schwarze Kristalle des Ba 4 As 2 O und Ba 4 P 2 O erhielt man durch dreitägiges Tempern der Präparate in Molybdänampullen unter Argon bei 1200 bzw. 1300°C. Sr 4 P 2 O, Sr 4 As 2 O und Ba 4 As 2 O kristallisieren im K 2 NiF 4 ‐Typ (I 4/m m m, Z = 2): Sr 4 P 2 O: a = 479,4(1) pm, c = 1598,5(4) pm, d 25 4 = 3,90; Sr 4 As 2 O: a = 483,1(1) pm, c = 1636,4(4) pm, d 25 4 = 4,46; Ba 4 As 2 O: a = 512,46(4) pm, c = 1733,6(1) pm, d 25 4 = 5,24. Ba 4 P 2 O ist rhombisch verzerrt (La 2 CuO 4 ‐Typ; Abma, Z = 4): a = 733,5(1) pm, b = 716,4(1) pm, c = 1673,2(3) pm, d 25 4 = 4,71. Der Einfluß der Größe des Pnictidions (Pn = P bis Bi) auf kristallchemische Eigenschaften der Verbindungen M 4 Pn 2 O mit gleichem Kation wird diskutiert. Preparation and Crystal Structure of the Alkaline Earth Pnictide Oxides Sr 4 P 2 O, Sr 4 As 2 O, Ba 4 P 2 O, and Ba 4 As 2 O Sr 4 P 2 O (light‐brown), Sr 4 As 2 O (red‐brown), Ba 4 As 2 O (grey‐black), and Ba 4 P 2 O (grey‐black) were prepared by the reaction of the metals, red phosphorus (arsenic), and metal oxide in molar ratios 3 : 2 : 1 in corundum crucibles sealed in quartz ampoules under argon (3 d 630°C, 2 d 1000°C, 2 d 1100°C). The compounds are microcrystalline, easily hydrolysable powders. Black single crystals of Ba 4 As 2 O and Ba 4 P 2 O were obtained by annealing specimens in molybdenum ampoules under argon (3 d 1200 and 1300°C resp.). Sr 4 P 2 O, Sr 4 As 2 O, and Ba 4 As 2 O crystallize in the K 2 NiF 4 ‐type structure; Ba 4 P 2 O is rhombically distorted and possesses the La 2 CuO 4 ‐type structure (Crystallographic data: see “Inhaltsübersicht”). The influence of the size of the pnictide ion (Pn = P to Bi) on crystal chemical properties of the compounds M 4 Pn 2 O with the same cation is discussed.