Inhaltsu È bersicht. Durch Umsetzung von NdCl 3 , Nd 2 O 3 und SiO 2 (molares Verha È ltnis: 1 : 4 : 6) la È ût sich bei 850°C in evakuierten Quarzglasampullen innerhalb von sieben Tagen das blaûviolette, hydrolysebesta È ndige Neodym(III)-Chlorid-ortho-Silicat Nd 3 Cl[SiO 4 ] 2 gewinnen. Wenn a È quimolare Mengen an NaCl als Fluûmittel zugesetzt werden, fallen dabei sta È bchen-bzw. pla È ttchenfo È rmige, transparente Einkristalle von zwei Modifikationen gleichzeitig an. Die dichtere von beiden (A-Nd 3 Cl[SiO 4 ] 2 ) kristallisiert monoklin (C2/c, Nr. 15; a = 1416,6(1), b = 638,79(6), c = 872,21(9) pm, b = 98,403(7)°; V m = 117,55 cm 3 /mol, Z = 4), wa È hrend man fu È r die weniger dichte (B-Nd 3 Cl[SiO 4 ] 2 ) orthorhombische Symmetrie (Pnma, Nr. 62; a = 709,36(7), b = 1815,7(2), c = 631,48 (6) pm; V m = 122,45 cm 3 /mol, Z = 4) antrifft. Beiden Strukturen liegen je zwei kristallographisch unterschiedliche Nd 3+ -Kationen zugrunde, die im A-Typ von neun (1 Cl ± und 8 O 2± ) bzw. zehn (2 Cl ± und 8 O 2± ), im B-Typ dagegen von nur jeweils acht (1 Cl ± und 7 O 2± bzw. 2 Cl ± und 6 O 2± ) Anionen umgeben sind. Dabei stellen sa È mtliche Sauerstoffteilchen beider Formen Bestandteile von diskreten ortho-Silicattetraedern ([SiO 4 ] 4± ) dar. Obwohl beide Kristallstrukturen aus alternierend angeordneten anionischen Doppelschichten {(Nd1) 2 [SiO 4 ] 2 } 2± und kationischen Einfachschichten {(Nd2)Cl} 2+ aufgebaut sind, liegt im A-Typ eine ho È here Vernetzung der Gitterbausteine vor, indem die Kationen von drei bzw. vier, im B-Typ jedoch nur von je zwei ortho-Silicatanionen u È ber Tetraederkanten koordiniert werden. Daraus resultiert eine um rund 4% ho È here Dichte von Nd 3 Cl[SiO 4 ] 2 im A-Typ (D x = 5,55 g/cm 3 ) gegenu È ber jener von B-Nd 3 Cl-[SiO 4 ] 2 (D x = 5,33 g/cm 3 ).Abstract. On reacting NdCl 3 , Nd 2 O 3 , and SiO 2 (molar ratio: 1 : 4 : 6) at 850°C in evacuated silica tubes, pale violet, hydrolysis resistant neodymium(III) chloride ortho-silicate Nd 3 Cl[SiO 4 ] 2 can be obtained within seven days. If equimolar amounts of NaCl are added as flux, rod-or plateletshaped, transparent single crystals of two modifications accumulate simultaneously. The one with the higher density (A-Nd 3 Cl[SiO 4 ] 2 ) crystallizes monoclinically (C2/c, no. 15; a = 1416.6(1), b = 638.79(6), c = 872.21(9) pm, b = 98.403(7)°; V m = 117.55 cm 3 /mol, Z = 4), whereas the one with the lower density (B-Nd 3 Cl[SiO 4 ] 2 ) exhibits orthorhombic symmetry (Pnma, no. 62; a = 709.36(7), b = 1815.7(2), c = 631.48(6) pm; V m = 122.45 cm 3 /mol, Z = 4). Two crystallographically independent Nd 3+ cations exist in each of both crystal structures, which in the A type are surrounded by nine (1 Cl ± + 8 O 2± ) and ten (2 Cl ± + 8 O 2± ), whilst those in the B type by only two times eight (1 Cl ± + 7 O 2± and 2 Cl ± + 6 O 2± ) anions, respectively. Thereby all oxygen atoms of both forms represent members of discrete ortho-silicate tetrahedra ([SiO 4 ] 4± ). Although both crystal structures are built of alternating anionic double layers {(Nd1)...
-009Pr(BO 2 ) 3 and PrCl(BO 2 ) 2 : Two Praseodymium meta-Borates in Comparison.-Single crystals of PrCl(BO 2 ) 2 (I) are obtained from the reaction of Pr 6 O 11 and PrCl 3 with excess B 2 O 3 (evacuated quartz tube, 850 • C, 7 d). The addition of NaCl as fluxing agent results in the formation of single crystals of Pr(BO 2 ) 3 (II) as the main product. (I) crystallizes in the triclinic space group P1 with Z = 2 and contains zigzag chains of corner-sharing BO 3 triangles. Pr 3+ is coordinated by three Cl − and seven O 2− anions forming a tetracapped trigonal prism. In the structure of compound (II) (monoclinic, space group C2/c, Z = 4) the boron atoms are present in both trigonal planar and tetrahedral oxygen coordination. The two types of polyhedra form chains via common corners. The coordination sphere of the Pr atoms is a bicapped square antiprism formed by ten O atoms.
Professor Josef Goubeau in memoriamInhaltsu È bersicht. Bei der Umsetzung von CeCl 3 mit CeO 2 , Cer und SiO 2 bzw. P 2 O 5 im molaren Verha È ltnis von 5 : 3 : 1 : 3 bzw. 8 : 3 : 1 : 2 in evakuierten Quarzglasampullen (7 d, 850°C) fallen Ce 3 Cl 5 [SiO 4 ] (orthorhombisch, Pnma; a = 1619,7(2), b = 415,26(4), 1423,6(1) pm; Z = 4) bzw. Ce 3 Cl 6 [PO 4 ] (hexagonal, P6 3 /m; a = 1246,36(9), c = 406,93(4) pm; Z = 2) als farblose, sta È bchenfo È rmige, luft-und wasserunempfindliche Einkristalle an. Ûberschu È ssiges Certrichlorid fo È rdert als Fluûmittel das Kristallwachstum und ist nach der Reaktion leicht durch Auswaschen mit Wasser wieder zu entfernen. Diskrete [SiO 4 ] 4± -bzw. [PO 4 ] 3± -Tetraeder bestimmen als isolierte Einheiten die Kristallstrukturen. Beide, das Chloridsilicat Ce 3 Cl 5 [SiO 4 ] und das Chloridphosphat Ce 3 Cl 6 [PO 4 ], zeigen strukturelle Øhnlichkeiten mit CeCl 3 (UCl 3 -Typ), indem man formal vier bzw. drei Cl ± -Anionen in der verdreifachten Formel (Ce 3 Cl 9 ) durch jeweils eine [SiO 4 ] 4± -bzw. [PO 4 ] 3± -Einheit ersetzt. Dadurch erho È ht sich die Koordinationszahl fu È r Ce 3+ von neun in CeCl 3 auf zehn in Ce 3 Cl 5 [SiO 4 ] und Ce 3 Cl 6 [PO 4 ], womit eine drastische Verringerung des molaren Volumens beim Ûbergang von Ce 3 Cl 9 (V m = 186,17 cm 3 /mol) zu Ce 3 Cl 5 [SiO 4 ] (V m = 144,15 cm 3 /mol) bzw. Ce 3 Cl 6 [PO 4 ] (V m = 164,84 cm 3 /mol) einhergeht. Die Koordinationspolyeder um Ce 3+ lassen sich als vierfach u È berkappte trigonale Prismen beschreiben, die zusa È tzlich zu je sieben Cl ± -Anionen jeweils noch drei Sauerstoffatome zweier ortho-Silicat-bzw. ortho-Phosphat-Tetraeder aufweisen. Ce 3 Cl 5 [SiO 4 ] and Ce 3 Cl 6 [PO 4 ]: A Chloride-Rich Chloride Silicate of Cerium as Compared to the PhosphateAbstract. By reacting CeCl 3 with CeO 2 , cerium and SiO 2 , or P 2 O 5 , respectively, in molar ratios of 5 : 3 : 1 : 3 or 8 : 3 : 1 : 2, respectively, in sealed evacuated silica tubes (7 d, 850°C) colorless, rod-shaped single crystals of Ce 3 Cl 5 [SiO 4 ] (orthorhombic, Pnma; a = 1619.7(2), b = 415.26(4), 1423.6(1) pm; Z = 4) and Ce 3 Cl 6 [PO 4 ] (hexagonal, P6 3 /m; a = 1246.36(9), c = 406.93(4) pm; Z = 2) are obtained as products insensitive to air and water. Excess cerium trichloride as flux promotes crystal growth and can be rinsed off again with water after the reaction. The crystal structures are determined by discrete [SiO 4 ] 4± or [PO 4 ] 3± tetrahedra as isolated units. Both, the chloride silicate Ce 3 Cl 5 [SiO 4 ] and the chloride phosphate Ce 3 Cl 6 [PO 4 ], exhibit structural similarities to CeCl 3 (UCl 3 type), when four or three Cl ± anions are each substituted formally by one [SiO 4 ] 4± or [PO 4 ] 3± unit, respectively, in the tripled formula (Ce 3 Cl 9 ). The coordination number for Ce 3+ is thus raised from nine in CeCl 3 to ten in Ce 3 Cl 5 [SiO 4 ] and Ce 3 Cl 6 [PO 4 ], along with a drastic reduction of the molar volume with the transition from Ce 3 Cl 9 (V m = 186.17 cm 3 /mol) to Ce 3 Cl 5 [SiO 4 ] (V m = 144.15 cm 3 /mol) and Ce 3 Cl 6 [PO ...
Sm3Cl[SiO4]2: A Chlorine‐poor Chloride Orthosilicate of Samarium Pale yellow, plate‐like single crystals of Sm3Cl[SiO4]2 (orthorhombic, Pnma; a = 701.74(8), b = 1800.8(2), c = 626.63(7) pm; Z = 4) are obtained upon the reaction of SmCl3, Sm2O3 and SiO2 (”︁Kieselgel”︁”︁) in 1 : 4 : 6 molar ratios, most advantageously in the presence of substantial amounts of NaCl as fluxing agent, after seven days at 850 °C in evacuated silica ampoules. The B‐type crystal structure (isotypic with e. g. Yb3Cl[SiO4]2) contains discrete orthosilicate tetrahedra [SiO4]4– which form anionic double layers ({(Sm1)2[SiO4]2}2–) with (Sm1)3+. These are alternatingly sheethed along [010] with cationic monolayers ({(Sm2)Cl}2+) consisting of (Sm2)3+ and Cl–. Both crystallographically independent Sm3+ cations exhibit coordination numbers of eight (Sm1: 1 Cl + 7 O; Sm2: 2 Cl + 6 O) with respect to the involved electronegative particles.
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