Dietrich Babel

Einkristallstrukturuntersuchungen an hexagonalen Fluorperowskiten AMIIF3 (MII = Mg, Mn, Fe, Co, Ni)

An Einkristallen von neun Fluorid-Phasen AMF3 wurden rontgenographisch die hexagonalen Perowskitstrukturen verfeinert, von RbNiF3 auch unterhalb von TC £ 145 K. Im hexagonalen 6 L-Typ (P63/mmc, Z = 6) kristallisieren: RbMgF3 (a = 585,7(1); c = 1426,0(1) pm), CsMnF3 (624,4(1); 1515,4(4) pm), CsFeF3 (616,8(1); 1488,4(6) pm), Rb0,63Cs0,37CoF3 (599,1(1); 1460,3(4) pm), RbNiF3 (128 K: 582,6(1); 1426,4(6) pm), Cs2BaLiNi2F9 (593,1(1); 1447,1(4) pm). Vom hexagonal-rhomboedrischen 9 L-Typ (R 3 m, Z = 9) sind CsCoF3 (620,1(1); 2264,0(7) pm) und bei niedrigeren Temperaturen bzw. unter Hochdruck prapariertes gelbes CsNiF3 (614,7(1); 2235,3(6) pm), wahrend das hellgrune CsNiF3 (625,5(1); 524,2(1) pm) dem 2 L-Typ angehort (P63/mmc, Z = 2). Das Auftreten dieser Strukturen und die in ihnen beobachteten Abstandsverhaltnisse, auch im Vergleich von Normal- und Hochdruckphasen, werden im Zusammenhang mit dem Toleranzfaktor diskutiert. Single Crystal Structural Studies at Hexagonal Fluoride Perovskites AMIIF3 (MII = Mg, Mn, Fe, Co, Ni) At single crystals of nine fluoride phases AMF3 the hexagonal perovskite structures were refined by X-ray methods, of RbNiF3 below TC £ 145 K, too. The hexagonal 6 L type (P63/mmc, Z = 6) is found at: RbMgF3 (a = 585.7(1); c = 1426.0(1) pm), CsMnF3 (624.4(1); 1515.4(4) pm), CsFeF3 (616.8(1); 1488.4(6) pm), Rb0.63Cs0.37CoF3 (599.1(1); 1460.3(4) pm), RbNiF3 (128 K: 582.6(1); 1426.4(6) pm), Cs2BaLiNi2F9 (593.1(1); 1447.1(4) pm). Of the hexagonal-rhombohedral 9 L type (R 3 m, Z = 9) are CsCoF3 (620.1(1); 2264.0(7) pm) and yellow CsNiF3 (614.7(1); 2235.3(6) pm), prepared at lower temperatures resp. under high pressure, whereas light green CsNiF3 (625.5(1); 524.2(1) pm) belongs to the 2 L type (P63/mmc, Z = 2). The occurence of these structures and the interatomic distances observed, comparing also normal and high pressure phases, are discussed in connection with the tolerance factor.

Die Kristallstruktur des Cyanospinells K2Cd(CN)4

The crystal structure of cubic K2Cd(CN)4 (a = 1286.01(9) pm, Fd 3̅ m, Z = 8) was determined from 175 independent X-ray single crystal reflections (w R = 0.0178). Regular [Cd(CN)4]2- tetrahedra (Cd - C = 222.5(3), C - N = 111.3(3) pm) and strongly trigonally elongated [KN6] octahedra ( K - N = 293.0(2) pm) are arranged in a normal spinel type manner.

Kristallstrukturen von Octacyanomolybdaten(IV). V. Quadratisch-antiprismatische [Mo(CN)8]-Koordination in den cyanoverbrückten Kupfer- und Cadmium-Amminkomplexen Cu2(NH3)8[Mo(CN)8] und Cd2(NH3)6[Mo(CN)8]·H2O/Crystal Structures of Octacyanomolybdates(IV). V. Square Antiprismatic [Mo(CN)8]-Coordination of the Cyano-Bridged Copper and Cadmium Ammine Complexes Cu2(NH3)8[Mo(CN)8] and Cd2(NH3)6[Mo(CN)8]·H2O

At single crystals of the cyano complexes Cu2(NH3)8[Mo(CN)8] (a = 934.1(4), b = 1595.9(3), c = 1391.9(4) pm, β = 90.57(2)°, monoclinic space group Cc, Z = 4) and Cd2(NH3)6[Mo(CN)8]·H2O (a = 1708.7(12), b = 1307.8(4), c = 942.9(3) pm, orthorhombic space group Pna21, Z = 4) X-ray structure determinations were performed at temperatures of about 175 K. Both compounds, prepared at about 275 K in aqueous ammonia solutions and easily decomposing, exhibit distorted square antiprismatic [Mo(CN)8]4- coordination of closely resembling dimensions (mean distances Mo-C: 215.7 and 215.3 pm, resp.). The anions are bridged by ammine cations to form chains in the copper and a three-dimensional framework in the cadmium compound. Some of the cyano bridges are strongly bent (C-N-MII as small as 124° and 130°, resp.). The distorted M coordination is square pyramidal and elongated octahedral in the case of the two copper atoms (Cu-N ranging from 197 to 257 pm, three and five ligands, respectively, being NH3). In the case of cadmium both metal atoms are octahedrally coordinated, one exhibiting mer-, the other fac-arrangement of three NH3 and three NC-ligands (Cd-N ranging from 229 to 247 pm, mean 235 pm for either cadmium atom). The findings are compared with related compounds and further details are discussed.

Struktur und Magnetismus von Fluoriden Cs2MCu3F10 (M = Mg, Mn, Co, Ni), Varianten des CsCu2F5‐Typs

Rontgenographische Strukturbestimmungen an Einkristallen zeigten, das die Verbindungen Cs2MCu3F10 mit Z = 2 in der Raumgruppe P21/n (Nr.14) (M = Mn) des CsCu2F5-Typs kristallisieren bzw. in deren Obergruppe I2/m (Nr.12) (M = Mg, Co, Ni). Cs2MgCu3F10: a = 714, 9(1), b = 736, 8(1), c = 940, 4(1) pm, b = 96, 29(1)°, (Mg-F: 199, 2 pm); Cs2MnCu3F10: a = 725, 1(1), b = 742, 7(1), c = 951, 0(2) pm, b = 97, 28(3)°, (Mn-F: 209, 1 pm); Cs2CoCu3F10: a = 717, 8(3), b = 739, 1(2), c = 939, 4(4) pm, b = 97, 49(2)°, (Co-F: 203, 1 pm); Cs2NiCu3F10: a = 716, 3(1), b = 737, 7(1), c = 938, 2(2) pm, b = 97, 09(1)°, (Ni-F: 201, 0 pm). Wie fur die Mg-Verbindung direkt bestimmt und allgemein aus den angegebenen mittleren Abstanden M-F zu schliesen, erfolgt die M-Substitution ganz uberwiegend in der oktaedrisch koordinierten Position der CsCu2F5-Struktur, deren Verzerrung dadurch wesentlich reduziert wird. In den verbleibenden Koordinationen [CuF4] und [CuF5] ist im Gegensatz zu CsCu2F5 ein F-Ligand fehlgeordnet, im Fall der Mn-Verbindung auch das pyramidal koordinierte Cu-Atom. Die magnetischen Eigenschaften sind komplex und deuten auf Frustration und Spinglas-Effekte. Nur bei den diamagnetisch mit M = Mg, Zn substituierten Varianten tritt kein Neelpunkt in Erscheinung, der fur M = Mn, Co, Ni, Cu bei 27, 23, 36 bzw. 55 K erreicht wird. Unterhalb dieser Temperaturen ist Ferri- bzw. schwacher Ferromagnetismus mit Hysterese zu beobachten. Structure and Magnetism of Fluorides Cs2MCu3F10 (M = Mg, Mn, Co, Ni), Variants of the CsCu2F5 Type X-ray structure determinations of single crystals showed that compounds Cs2MCu3F10 crystallize with Z = 2 in space group P21/n (No.14) (M = Mn) of the CsCu2F5 type resp. in its supergroup I2/m (No.12) (M = Mg, Co, Ni). Cs2MgCu3F10: a = 714.9(1), b = 736.8(1), c = 940.4(1) pm, b = 96.29(1)°, (Mg-F: 199.2 pm); Cs2MnCu3F10: a = 725.1(1), b = 742.7(1), c = 951.0(2) pm, b = 97.28(3)°, (Mn-F: 209.1 pm); Cs2CoCu3F10: a = 717.8(3), b = 739.1(2), c = 939.4(4) pm, b = 97.49(2)°, (Co-F: 203.1 pm); Cs2NiCu3F10: a = 716.3(1), b = 737.7(1), c = 938.2(2) pm, b = 97.09(1)°, (Ni-F: 201.0 pm). As determined directly for the Mg compound and generally concluded from the average distances M-F noted, M substitution concerns mainly the octahedrally coordinated position of the CsCu2F5 structure, the distortion of which is very much reduced thereby. Within the remaining [CuF4] and [CuF5] coordinations, in contrast to CsCu2F5, one F ligand is disordered, in case of the Mn compound the pyramidally coordinated Cu atom, too. The magnetic properties are complex and point to frustration and spin glass effects. Only at the diamagnetically substituted variants with M = Mg, Zn no Neel point appears, which is reached at 27, 23, 36 and 55 K for M = Mn, Co, Ni and Cu, resp. At lower temperatures ferri- resp. weak ferromagnetism and hysteresis is observed.

Kristallstrukturuntersuchungen an den Alkali- und BariumÜbergangsmetallfluoriden RbK2Mn2F7, BaNiF4 und einer 5 : 3-Phase im System BaLiF3/NaCoF3

An Einkristallen der Verbindungen RbK2Mn2F7, BaNiF4 und einer Phase 0,618 BaLiF3/0,382 NaCoF3 wurden rontgenographisch die Kristallstrukturen verfeinert. RbK2Mn2F7 ist tetragonal (a = 421,1(1), c = 2188,3(2) pm, I4/mmm, Z = 2) und kristallisiert im Sr3Ti2O7-Typ. Die mittleren Abstande betragen Mn–F: 210,7 pm im [MnF6]-Oktaeder und A–F: 290,6 bzw. 297,1 pm fur die [AF9]- bzw. [AF12]-Koordination der gemischt besetzten Alkali-Positionen (A = Rb/3 + 2 K/3). BaNiF4 (a = 413,7(1), b = 1443,1(3), c = 578,1(1) pm, Cmc21, Z = 4) ist vom orthorhombischen BaZnF4-Typ; Ni–F: 200,3 pm, Ba–F: 274,3 pm fur KZ6 bzw. KZ9. Die aus einem 1 : 1-Ansatz BaLiF3/NaCoF3 isolierte Phase mit der angenaherten Zusammensetzung 5 : 3 ist kubisch (a = 801,8(1) pm, Im3, Z = 8 AMF3) und bildet eine stark fehlgeordnete Perowskit-Uberstruktur, deren Merkmale diskutiert werden. Crystal Structural Studies of the Alkali and Barium Transition Metal Fluorides RbK2Mn2F7, BaNiF4, and a 5 : 3-Phase of the System BaLiF3/NaCoF3 At single crystals of the compounds RbK2Mn2F7, BaNiF4, and of a phase 0.618 BaLiF3/0.382 NaCoF3 the X-ray crystal structures were refined. RbK2Mn2F7 is tetragonal (a = 421.1(1), c = 2188.3(2) pm, I4/mmm, Z = 2) and belongs to the Sr3Ti2O7 type. The average distances are Mn–F: 210.7 pm for the [MnF6] octahedron and A–F: 290.6 resp. 297.1 pm for the [AF9] resp. [AF12] coordination of the mixed alkali positions (A = Rb/3 + 2 K/3). BaNiF4 (a = 413.7(1), b = 1443.1(3), c = 578.1(1) pm, Cmc21, Z = 4) is of the orthorhombic BaZnF4 type; Ni–F: 200.3 pm, Ba–F: 274.3 pm for CN6 and CN9, resp.. The phase of approximate composition 5 : 3, isolated from a 1 : 1 batch BaLiF3/NaCoF3, is cubic (a = 801.8(1) pm, Im3, Z = 8 AMF3) and forms a strongly disordered perovskite super-structure, the features of which are discussed.

Röntgenstrukturuntersuchungen an Elpasolith-verwandten Hexacyanokomplexen [N(CH3)4]2A[M(CN)6] (A = Rb, Tl; M = Cr, Fe) / X-Ray Structure Investigations of Elpasolite Related Hexacyano Complexes [N(CH3)4]2A[M(CN)6] (A = Rb, Tl; M = Cr, Fe)

Abstract Single crystals were prepared and X -ray structure determinations performed of the hexagonal com pounds (R3̄m, Z = 3) [N(CH3)4]2RbCr(CN)6 (a = 895.9, c = 2176.4 pm), [N (CH3)4],TlCr(CN)6 (a = 894.0, c = 2168.4 pm), [N(CH3)4],RbFe(CN)6 (a = 886.7, c = 2149.9 pm ) and of monoclinic [N(CH3)4]2TlFe(CN)6 (C2/c, Z = 4; a = 1511.4, b = 884.8, c = 1525.9 pm , β = 110.0°). The structure of the hexagonal complexes is closely related to that of cubic elpasolites, showing, however, orientational disorder of the tetramethylammonium groups. Within the monoclinic TIFe-compound this group has fixed orientation, which makes some of the Fe-CN-Tl bridges bent, contrary to the linear M-CN -A array within the hexagonal compounds. Details and relations are discussed with respect to similar hexacyano complexes.

Zur Kristallstruktur der Cyanoelpasolithe [N(CH3)4]2CsCo(CN)6 und [H3NCH3]2NaFe(CN)6 / Concerning the Crystal Structures of the Cyano-Elpasolites [N(CH3)4]2CsCo(CN)6 and [H3NCH3]2NaFe(CN)6

Abstract Single crystals of the cyano complexes [N(CH3)4]2CsCo(CN)6 and [H3NCH3]2NaFe(CN)6 were prepared and their structures determined by X-ray methods. The cobalt compound is monoclinic, a =885.5(1), b = 892.6(2), c = 1259.9(5) pm, β = 90.29(4)°, space group I2/m, Z = 2; R1 = 0.048 for 861 independent reflections. The resulting average distances in the nearly undistorted octahedra are Co - C = 189.8, C - N = 114.1, Cs - N = 325.6 pm. The iron compound exhibits a cubic elpasolite type structure, a = 1105.2(1) pm, space group Fm 3m , Z = 4; R1 = 0.040 for 127 independent reflections; Fe - C = 193.4(6), Na - N = 247.7(8) pm. The orientation of the librating tetramethyl-ammonium group within the cages of the cobalt compound and the disorder of the monomethyl-ammonium cation around the special site (1/4, 1/4, 1/4) of the iron complex are discussed.

Die Kristallstrukturen der Eisen- und Cobalt-Hexacyanokomplexe Rb2LiM(CN)6 und Rb2NaM(CN)6 / The Crystal Structures of the Iron- and Cobalt-Hexacyanocomplexes Rb2LiM(CN)6 and Rb2NaM(CN)6

Abstract The crystal structures of four isotypic cyano complexes, belonging to the monoclinic type of cryolite (P21/n, Z = 2), were determined by single crystal X-ray methods and in one case also by neutron diffraction: Rb2LiFe(CN)6 (a = 717.3, b = 748.0, c = 1030.2 pm, β = 90.24°; Fe - C = 193.6, C - N = 114.5, Li - N = 227.0 pm), Rb,NaFe(CN)6 (a = 724.5, b = 772.5, c = 1055.2 pm, β = 90.39°; Fe - C = 193.9, C - N = 114.2, Na - N = 250.4 pm), Rb,LiCo(CN)6 (a = 715.5, b = 741.2, c = 1025.0 pm, β = 90.14°; Co - C = 189.6, C - N = 114.3, Li - N = 226.9 pm), Rb2NaCo(CN)6 (a = 722.5, b = 766.3, c = 1049.2 pm, β = 90.33°; Co - C = 189.9 (188.8), C - N = 113.4 (7/5.5), Na - N = 250.6 (249.6 pm). The irregular [RbN8l coordination polyhedra exhibit average distances close to Rb - N = 336 pm. Details are discussed and the results compared with those of related compounds

Die Kristallstrukturen von Na2CoFeF7 und einer zweiten Modifikation von Na2CuFeF7: Eine weitere Weberit-Variante / The Crystal Structures of Na2CoFeF7 and a Second Modification of Na2CuFeF7: Another Weberite Variant

The monoclinic weberites Na2CoFeF7 (a = 1262.2(10), b = 736.0(4), c = 2451.6(20) pm, β = 99.71(5)°) and a second modification of Na2CuFeF7 (a = 1244.4(2), b = 734.3(1), c = 2467.2(5) pm, β = 99.27(3)°), crystallize isotypically in space group C 2/c, Ζ = 16. The structure is an intermediate type between orthorhombic and trigonal weberites, characterized by pairs ofparallel chains of octahedra [MF4F2/2]3- (M = Co, Cu) which run in turn along [110] and [110]. The average distances are Fe-F = 192 pm in the [FeF63- octahedra of both compounds. Considerable splitting of distances occurs in the [CoF6- octahedra (av. Co-F = 201 pm), and by Jahn-Teller distortion even more in those of [CuFJ4- (av. Cu-F = 199 pm). One of the copper surroundings is (pseudo)tetragonally elongated (av. 209/194 pm), the other exhibits an unusual splitting into three long and three short bonds (av. 204/193 pm) in meridional positions. Some structural relations are discussed.

Hydratisierte Cyanoelpasolithe: Die Kristallstrukturen von (NMe4)2Li(H2O)2[Cr(CN)6] und (NMe4)2Na(H2O)[M(CN)6] (M = Cr, Co) / Hydrated Cyano Elpasolites: The Crystal Structures of (NMe4)2Li(H2O)2[Cr(CN)6] and (NMe4)2Na(H2O)[M(CN)6] (M = Cr, Co)

The results of single crystal X-ray structure determinations are reported for monoclinic (NMe4)2Li(H2O)2[Cr(CN)6] (a = 1736.7(2), = 888.0(1), c = 1659.3(1) p m ,β = 119.33(1)°; C2/c, Z = 4) and orthorhombic (NMe4),Na(H2O)[Cr(CN)6] (a = 960.0(2), b = 885.0(2), c = 1269.8(3) pm; Pnmm, Z = 2) and (NMe4)2Na(H2O)[Co(CN)6] (a = 1854.5(4), b = 853.5(1), c = 1328.7(3) pm; Pnma, Z = 4), the latter exhibiting a superstructure of the NaCr compound. The average distances within the hexacyano groups are Cr-C: 207.8 resp. 208.3 pm and Co-C: 189.5 pm. The alkali ions are incorporated into the elpasolite-like arrangement of the bigger ions as di- or monohydrated species [Li(H2O)2]+ and [Na(H2O)]+ resp., becoming tetrahedrally coordinated [LiO2N2] and [NaON3] within the lattice and fixed by hydrogen bridges O-H...N as well. Some structural details and relations are discussed.