Ute Ch. Rodewald

Trapping of Tin(II) and Lead(II) Homologues of Carbon Monoxide by a Benzannulated Lutidine-Bridged Bisstannylene

The reaction of the benzannulated bisstannylene ligand 2 with Sn O or Pb O generated in situ gave the pincer complexes 3 and 4. Both complexes have been characterized by X-ray diffraction and multinuclear NMR spectroscopy. A divalent state has been found by Mössbauer spectroscopy for the tin atoms in complexes 3 and 4.

TERNARY RARE EARTH TRANSITION METAL ZINC COMPOUNDS RT2ZN20 WITH T = FE, RU, CO, RH, AND NI

Forty eight new compounds RT2Zn20 were prepared by annealing cold-pressed pellets of the elemental components in an argon atmosphere. They crystallize with the cubic CeCr2Al20 type structure (Fd3̅̅m , Z = 8), which was refined from single-crystal diffractometer data of TbFeiZn20 (a = 1411.1(1) pm ), YRu2Zn20 (a = 1422.6(1) pm ), DyRu2Zn20 (a = 1422.1(1) pm), GdCo2Zn20 (a = 1406.0(1) pm ), DyRh2Zn20 (a = 1418.2(1) pm ), and TmNi2Zn20 (a= 1401.6(1) pm) to conventional residuals varying betw een R = 0.011 and R - 0.024. The com pounds have a tendency for tw inning, thus m im icking hexagonal sym metry, with the cubic [111] axis as the axis w ith the pseudohexagonal symmetry. M inor inconsistencies in the cell volum es of these com pounds indicate slight deviations from the ideal com position. N evertheless, the five atom ic sites of this structure w ere found to be fully occupied w ithin the error lim its w ith the exception of one zinc site of TmNi2Zn20. The coordination for the site of the rare earth atom s is a Frank-K asper polyhedron with coordination num ber (CN) 16. The transition metal atom s occupy a site w ith icosahedral zinc coordination (CN 12). Two of the three zinc sites are in pentagonal prism atic coordination of zinc atom s, capped by rare earth and/or transition metal atom s (CN 12), w hile the third zinc site has 12 zinc neighbors form ing a hexagonal prism , w hich is capped by tw o rare earth atom s (CN 14).

Crystal Structure and Properties of Some Filled and Unfilled Skutterudites: GdFe4P12, SmFe4P12, NdFe4As12, Eu0.54Co4Sb12, Fe0.5Ni0.5P3, CoP3, and NiP3

The new cubic compound Fe0.5Ni0.5P3 (a = 775.29(5) pm) as well as the known compounds CoP3 and NiP3 were synthesized from the elemental components using tin as a flux. Their skutterudite (CoAs3) type structures were refined from single-crystal X-ray data. The new compound GdFe4P12 was prepared by reaction of an alloy Gd1/3Fe2/3 with phosphorus in a tin flux. Its cubic “filled” skutterudite (LaFe4P12 type) structure was refined from single-crystal X-ray data: a = 779.49(4) pm, R = 0.019 for 304 structure factors and 11 variable parameters. SmFe4P12 shows Van Vleck paramagnetism while GdFe4P12 is a soft ferromagnet with a Curie temperature of TC = 22(5) K. Both are metallic conductors. The new isotypic polyarsenide NdFe4As12 (a = 830.9(1) pm) was obtained by reacting NdAs2 with iron and arsenic in the presence of a NaCl/KCl flux. The new isotypic polyantimonide Eu0.54(1)Co4Sb12 (a = 909.41(8) pm) was prepared by reaction of EuSb2 with cobalt and antimony. Its structure was refined from single-crystal X-ray data to a residual of 0.024 (137 F values, 12 variables). A comparison of the Fe–P and P–P bond lengths in the compounds AFe4P12, where the A atoms (A = Ce, Eu, Gd, Th) have differing valencies, suggests that the Fermi level cuts through Fe–P bonding and P–P antibonding bands. Kristallstruktur und Eigenschaften einiger gefullter und ungefullter Skutterudite: GdFe4P12, SmFe4P12, NdFe4As12, Eu0,54Co4Sb12, Fe0,5Ni0,5P3, CoP3 und NiP3 Die neue kubische Verbindung Fe0,5Ni0,5P3 (a = 775,29(5) pm) sowie die bekannten Verbindungen CoP3 und NiP3 wurden aus den Elementen in einer Zinn-Schmelze synthetisiert. Ihre Kristallstruktur (Skutterudit-Typ, CoAs3) wurde anhand von Einkristall-Diffraktometerdaten verfeinert. Die neue Verbindung GdFe4P12 wurde durch Reaktion einer Legierung Gd1/3Fe2/3 mit Phosphor unter Verwendung von Zinn als Flux hergestellt. Ihre kubische „gefullte” Skutterudit-Struktur (LaFe4P12-Typ) wurde aus EinkristallDiffraktometerdaten verfeinert: a = 779,49(4) pm, R = 0,019 fur 304 Strukturfaktoren und 11 variable Parameter. SmFe4P12 zeigt Van Vleck-Paramagnetismus und GdFe4P12 ist ein weicher Ferromagnet mit einer Curie-Temperatur von TC = 22(5) K. Beide sind metallische Leiter. Das neue isotype Polyarsenid NdFe4As12 (a = 830,9(1) pm) wurde dargestellt durch Reaktion von NdAs2 mit Eisen und Arsen mit Hilfe einer NaCl/KCl-Schmelze. Das neue isotype Polyantimonid Eu0,54(1)Co4Sb12 (a = 909,41(8) pm) wurde durch Reaktion von EuSb2 mit Cobalt und Antimon erhalten. Seine Struktur wurde aus Einkristall-Diffraktometerdaten zu einem Restwert von 0,024 verfeinert (137 F-Werte, 12 Variable). Ein Vergleich der Fe–P- und P–P-Bindungslangen in den Verbindungen AFe4P12, in welchen die A-Atome (A = Ce, Eu, Gd, Th) unterschiedliche Valenzen haben, legt nahe, dass das Fermi-Niveau in der Hohe von bindenden Fe–P- und antibindenden P–P-Bandern liegt.

Large reversible magnetocaloric effect due to a rather unstable antiferromagnetic ground state in Er4NiCd

Er4NiCd crystallizes with the Gd4RhIn type structure, space group F (4) over bar 3m, a=1333.3 pm. The nickel atoms have trigonal prismatic rare earth coordination. Condensation of the NiEr6 prisms leads to a three-dimensional network which leaves voids that are filled by regular Cd-4 tetrahedra. Er4NiCd shows Curie-Weiss behavior above 50 K with T-N=5.9 K. At field strength of 4 kOe a metamagnetic step is visible, together with the positive paramagnetic Curie-temperature (7.5 K) indicative for the rather unstable antiferromagnetic ground state. Therefore, a large reversible magnetocaloric effect (MCE) near the ordering temperature occurs and the values of the maximum magnetic-entropy change -Delta S-M(max) reach 18.3 J kg(-1) K-1 for the field change of 5 T with no obvious hysteresis loss around 17 K. The corresponding RCP of 595 J kg(-1) is relatively high as compared to other MCE materials in that temperature range. These results indicate that Er4NiCd could be a promising system for magnetic refrigeration at temperatures below liquid H-2

Metallated ketenimines: Deprotonation of N-isopropyl-diphenylketenimine and subsequent trapping reactions with electrophiles A theoretical and experimental study

Abstract Deprotonation of N -isopropyl-diphenylketenimim 1 maybe achieved by surplus strong organic base (2,2,6,6-tetramethylpiperidine, n-butyllithium, potassium tert. butylate in tert. butyhnethyl ether). The resulting organometallic suspension is investigalled by means of fWpingreactions using various eleetrophiles. From the structures of the trapping products obtained the intermediacy of a substituted 1-methyleno-2-azaallyl anion 9 and of a 3-azapentadienyl anion 10 is deduced. Thus, proton sources yield a mixture of the 2-azabutadiene 2 together with two dimenc products, the 3-azahexatriew 3 and the heterocyclus 4 . Methyl iodide leads to the formation of a cross-conjugated dimeric product 5. The 2-azabutadiene derivatives 6 and 7 are the trapping products using trimethylacetyl chloride or dimethyl disulfide, resp., as electrophiles, exiibiting multiple addition to intermediate substituted 3-azapentadienyl anion systems. Quantum chemical calculations (MNDO, PM3, ab initio -methods) are used for the prediction of the gas phase acidities of N -isopropyfformimine and N -isopropylketenimine as model systems; the structures obtained by complete geometry optimizations of the postulated monomeric anions and lithium compounds are discussed.

Gd3Pt4In12 and Tb3Pt4In12 — New Ternary Indides with Condensed Distorted [PtIn6] Trigonal Prisms

The ternary indium compounds Gd3Pt4In12 and Tb3Pt4In12 were synthesized from an indium flux. Arc-melted precursor alloys with the starting compositions ∼GdPtIn4 and ∼TbPtIn4 were annealed with a slight excess of indium at 1200 K followed by slow cooling (5 K/h) to 870 K. Both compounds were investigated by X-ray powder diffraction: a = 990.5(1), c = 1529.5(3) pm for Gd3Pt4In12 and a = 988.65(9), c = 1524.0(1) pm for Tb3Pt4In12. The structure of the gadolinium compound was solved and refined from single crystal X-ray data: P3¯m1, wR2 = 0.0470, 1469 F2 values and 62 variable parameters. Both crystallographically different platinum sites have a slightly distorted trigonal prismatic indium coordination. These [PtIn6] prisms are condensed via common edges and corners forming a complex three-dimensional [Pt12In32] network. The gadolinium, In1 and In7 atoms fill cavities within this polyanion. Tb3Pt4In12 is isotypic with the gadolinium compound. Gd3Pt4In12 und Tb3Pt4In12 — Neue ternare Indide mit verzerrten, kondensierten trigonalen [PtIn6] Prismen Die ternaren Indiumverbindungen Gd3Pt4In12 und Tb3Pt4In12 wurden in Indiumschmelzen synthetisiert. Lichtbogengeschmolzene Precursor-Legierungen der Ausgangszusammensetzungen ∼GdPtIn4 und ∼TbPtIn4 wurden mit einem leichten Uberschus an Indium auf 1200 K erhitzt und mit 5 K/h langsam auf 870 K abgekuhlt. Beide Verbindungen wurden uber Rontgen-Pulverdaten charakterisiert: a = 990, 5(1); c = 1529, 5(3) pm fur Gd3Pt4In12 und a = 988, 65(9); c = 1524, 0(1) pm fur Tb3Pt4In12. Die Struktur der Gadoliniumverbindung wurde anhand von Einkristall-Rontgendaten gelost und verfeinert: P3¯m1, wR2 = 0, 0470; 1469 F2-Werte und 62 variable Parameter. Beide kristallographisch unterschiedlichen Platinatome haben eine leicht verzerrte, trigonal-prismatische Indiumkoordination. Die trigonalen [PtIn6] Prismen sind uber gemeinsame Ecken und Kanten zu einem komplexen, dreidimensionalen [Pt12In32] Netzwerk verknupft. Die Gadolinium-, In1- und die In7-Atome fullen kafigartige Lucken innerhalb dieses Polyanions. Tb3Pt4In12 ist isotyp zur Gadoliniumverbindung.

Lanthanoid AntimonidesLn2Sb5 (Ln = Sm, Gd, Tb, Dy) and Rationalization of Chemical Bonding within the Antimony Polyanion by Combining the Zintl-Klemm Concept with Bond-Length Bond-Strength Relationships

The title compounds are formed by peritectic reactions. Single crystals could be isolated from samples with high antimony content. Their structure was determined for Dy2Sb5 from four-circle X-ray diffractometer data: P21/m, a = 1306.6(1) pm, b = 416.27(4) pm, c = 1458.4(1) pm, β = 102.213(8)°, Z = 4, R = 0.061 for 2980 structure factors and 86 variable parameters. All dysprosium atoms have nine antimony neighbors forming tricapped trigonal prisms with Dy–Sb distances varying between 308 and 338 pm. The antimony atoms occupy ten different sites with greatly varying coordination. One extreme case is an antimony atom surrounded only by dysprosium atoms in trigonal prismatic arrangement, the other one is an antimony atom in distorted octahedral antimony coordination. The various antimony-antimony interactions (with Sb–Sb distances varying between 284 and 338 pm) are rationalized by combining the Zintl-Klemm concept with bond-length bond-strength considerations. Lanthanoid PolyantimonideLn2Sb5 (Ln = Sm, Gd, Tb, Dy) und Interpretation der chemischen Bindung innerhalb des Polyanions durch eine Kombination des Zintl-Klemm-Konzepts mit Bindungslange–Bindungsstarke-Beziehungen Die Titelverbindungen bilden sich durch peritektische Reaktionen. Einkristalle konnten aus Proben mit hohem Antimongehalt isoliert werden. Ihre Kristallstruktur wurde fur Dy2Sb5 mittels Rontgen-VierkreisDiffraktometerdaten bestimmt: P21/m, a = 1306.6(1) pm, b = 416.27(4) pm, c = 1458.4(1) pm, β = 102.213(8)°, Z = 4, R = 0.061 fur 2980 Strukturfaktoren und 86 variable Parameter. Alle Dysprosiumatome haben neun Antimonnachbarn, welche dreifach uberkappte trigonale Prismen bilden mit von 308 bis 338 pm variierenden Dy–Sb Abstanden. Die Antimonatome besetzen zehn Punktlagen mit sehr unterschiedlicher Koordination. Ein Extremfall ist ein Antimonatom umgeben nur von Dysprosiumatomen in trigonal prismatischer Anordnung, ein anderer ist ein Antimonatom mit verzerrt-oktaedrischer Antimon-Umgebung. Die unterschiedlichen Antimon–Antimon-Wechselwirkungen (mit Sb–Sb Abstanden von 284 bis 338 pm) werden durch Kombination des Zintl-Klemm-Konzepts mit Bindungslange–Bindungstarke-Beziehungen beschrieben.

Structure and Properties of the Stannide Eu2Au2Sn5, and its Relationship with the Family of BaAl4-Related Structures

The stannide Eu2Au2Sn5 was prepared by high-frequency melting of the elements in a sealed tantalum tube. The structure of Eu2Au2Sn5 was refined from single crystal X-ray data: P21/m, a = 928.6(2), b = 465.8(2), c = 1042.9(3) pm, ß = 92.28(2)°, wR2 = 0.0653, 1220 F2 values and 56 variables. The structure of Eu2Au2Sn5 is of a new type, it can be considered as an ordered defect variant of the BaAl4 type. Due to the ordered defects, the coordination number (CN) of the two crystallographically different europium sites is reduced from CN 16 to CN 14. The gold and tin atoms in Eu2Au2Sn5 form a complex three-dimensional [Au2Sn5] polyanion in which the europium atoms are embedded. Within the polyanion short Au-Sn and Sn-Sn distances are indicative of strongly bonding Au-Sn and Sn-Sn interactions. A detailed group-subgroup scheme for various ordered and defect variants of the BaAl4 family is presented. Eu2Au2Sn5 shows Curie-Weiss behavior above 50 K with an experimental magnetic moment of 7.90(5) μB/Eu, indicating divalent europium. Antiferromagnetic ordering is detected at 5.8(5) K at low fields and a metamagnetic transition occurs at a critical field of 1.4(2) T. Eu2Au2Sn5 is a metal with a specific resistivity of 150±20 μfΩcm at room temperature. The results of 151Eu and 119Sn Mössbauer spectroscopic experiments are compatible with divalent europium and show complex hyperfine field splitting with a transferred magnetic hyperfine field at the tin nuclei at low temperature.

Intermetallic Cerium Compounds with Ordered U3Si2 Type Structure

Abstract New intermetallic cerium compounds Ce2T2Mg (T = Ni, Cu, Pd), C2T2Cd (T=Pd, Pt, Au), and C2T2Pb (T = Pt, Au) were prepared by reaction of the elements in sealed tantalum tubes in a high-frequency furnace. Most C2T2X (X = Mg, Cd, Pb) compounds are stable after annealing at about 1000 K, while Ce2Pd2Mg is obtained as single phase only after melting and quenching. A thermal treatment at about 1000 K leads to decomposition in CePdMg and CePd. The eight compounds were investigated by X-ray diffraction both as powders and single crystals, and most structures were refined from single crystal data. They adopt an ordered U3Si2 type structure with space group P4/mbm: a = 759.6(1), c = 376.71 (9) pm, wR2 = 0.0562, 294 F2 values, 12 parameters for Ce2Ni2Mg, a = 787.41(9), c = 387.23(7) pm, wR2 = 0.0438, 222 F2 values, 12 parameters for Ce2Cu2Mg, a = 777.14(8), c = 400.03(7) pm, wR2 = 0.0276, 221 F2 values, 13 parameters for Ce2Pd2.03Mg0.97, a = 777.90(6), c = 393.28(6) pm, wR2 = 0.0360,317 F2 values, 12 parameters for Ce2Pd2Cd, and a = 779.90(7), c = 389.97(7) pm, wR2 = 0.0453, 315 F2 values, 12 parameters for Ce2Pt2Cd. Refinement of the occupancy parameters revealed full occupancy for most sites. A mixed palladium/magnesium (97 % Mg / 3 % Pd) occupancy was observed only for the 2a site of Ce2Pd2.03Mg0.97, indicating a small homogeneity range for this compound. Ce2Au2Cd (a = 804.93(7), c =393.36(6) pm) and the plumbides Ce2Pt2Pb (a = 794.63(7), c = 381.50(6) pm) and Ce2Au2Pb (a = 810.70(7), c = 394.85(7) pm) were characterized through their Guinier powder data. The structures of the Ce2T2X compounds can be interpreted as an intergrowth of distorted AIB2 and CsCl related slabs of compositions CeT2 and CeX. The course of the lattice parameters and chemical bonding within the series of Ce2T2X compounds are briefly discussed.

The Crystal Structure of the Potential Ferroelectric Calcium Rhenate(VI, VII) Ca11Re4O24 and its Relation to the Structure of Sr11Os4O24

The title compound was prepared in well-crystallized form by thermal decomposition of Ca5Re2O12. Its structure was determined from single-crystal X-ray diffractometer data: I41, a = 1107.0(1), c = 1609.3(1) pm, Z = 4, R = 0.056 for 4565 structure factors and 119 variable parameters. The calcium atoms occupy seven different sites with 8, 9, or 10 oxygen neighbors. The two different rhenium atoms are octahedrally coordinated by oxygen atoms with average Re-O distances of 193.1 and 187.7 pm for the six- and seven-valent rhenium atoms, respectively. The compound shows Curie-Weiss behavior with a magnetic moment of μexp = 1.15(±0.10) μB per Re(VI) atom. The structure is closely related to that of Sr11Os4O24 which, however, crystallizes in the space group I2/a. The difference between the two structures arises through the higher coordination numbers of the strontium atoms. It is suggested that at high temperature both compounds crystallize in the common higher symmetry space group I4/a. Since Ca11Re4O24 crystallizes in the pyroelectric class 4 this compound is expected to be ferroelectric.