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Anja-Verena Mudring

Publications and source records attributed to Anja-Verena Mudring.

13 recordsLinked to original sources
PubMed2006

Cluster-type basic lanthanide iodides [M6(mu6-O)(mu3-OH)8(H2O)24]I8(H2O)8 (M = Nd, Eu, Tb, Dy).

Ln6(mu6-O)(mu3-OH)8(H2O)24]I8(H2O)(8) (Ln = Nd, Eu, Tb, Dy) compounds are obtained as the final hydrolysis products of lanthanide triiodides in an aqueous solution. Their X-ray crystal structure features a body-centered arrangement of oxygen-centered {Ln6X8}8+ cluster cores: [Nd6(mu6-O)(mu3-OH)8(H2O)24]I8(H2O)8 [Pearson code oP156, orthorhombic, Pnnm (No. 58), Z = 2, a = 1310.4(3) pm, b = 1502.1(3) pm, c = 1514.9(3) pm, 3384 reflections with I0 > 2sigma(I0), R1 = 0.0340, wR2 = 0.0764, GOF = 1.022, T = 298(2) K], [Eu6(mu6-O)(mu3-OH)8(H2O)24]I8(H2O)8 [Pearson code oP156, orthorhombic, Pnnm (No. 58), Z = 2, a = 1306.6(2) pm, b = 1498.15(19) pm, c = 1499.41(18) pm, 4262 reflections with I0 > 2sigma(I0), R1 = 0.0540, wR2 = 0.0860, GOF = 0.910, T = 298(2) K], [Tb6(mu6-O)(mu3-OH)8(H2O)24]I8(H2O)8 [Pearson code oP156, orthorhombic, Pnnm (No. 58), Z = 2, a = 1296.34(5) pm, b = 1486.13(7) pm, c = 1491.88(6) pm, 4182 reflections with I0 > 2sigma(I0), R1 = 0.0395, wR2 = 0.0924, GOF = 1.000, T = 298(2) K], and [Dy6(mu6-O)(mu3-OH)8(H2O)24]I8(H2O)8 [Pearson code oP156, orthorhombic, Pnnm (No. 58), Z = 2, a = 1296.34(5) pm, b = 1486.13(7) pm, c = 1491.88(6) pm, 3329 reflections with I0 > 2sigma(I0), R1 = 0.0389, wR2 = 0.0801, GOF = 0.992, T = 298(2) K.

Crystallography, X-Ray↗
PubMed2006

Crystal engineering in ionic liquids. The crystal structures of [Mppyr]3[NdI6] and [Bmpyr]4[NdI6][Tf2N].

Single crystals of [mppyr][NdI6] and [bmpyr][NdI6][Tf2N] are the first surprising examples of how the cation of an ionic liquid determines the compound formation from an ionic liquid. Depending upon the variation of the length of the alkyl chain of the quaternary pyrrolidinium cation (C3 and C4, respectively), incorporation of the anion of the ionic liquid, [Tf2N]-, can either be evoked or suppressed.

Journal Article↗
PubMed2006

Homoleptic alkaline earth metal bis(trifluoromethanesulfonyl)imide complex compounds obtained from an ionic liquid.

The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen atoms of the same ligands are linking the Ba2+ cations to infinite (infinity)(1)[Ba(Tf2N)3] chains.

Journal Article↗
PubMed2005

Lone pair effect in thallium(I) macrocyclic compounds.

The role of the inert (lone) pair of electrons in thallium(I) salts is studied by comparison of the compounds [Tl@18-crown-6]+ X- (X = TlI4, ClO4) and [K@18-crown-6]+ ClO4-. In contrast to common introductory chemistry textbook opinions, the paradigm that s-p hybridization is a prerequisite for an inert electron pair to become stereochemically active in compounds of the heavier main group elements has to be revised. Instead, an inert pair of electrons is expected to become stereochemically involved whenever it is forced to participate in antibonding orbital interactions with its surroundings, and there is the possibility for a structural distortion that minimizes these repulsive forces. The structural distortion will occur to such an extent that repulsive orbital interactions and attractive electrostatic interactions counterbalance. Our results also provide an explanatory background for many of the rules of thumb that are found in the literature about why and when an inert electron pair is expected to become stereochemically active in a certain compound.

Journal Article↗
PubMed2004

Unusual electronic and bonding properties of the Zintl phase Ca5Ge3 and related compounds. A theoretical analysis.

Theoretical reasons for metallic behavior among diverse Zintl phases have generally not been pursued at an advanced level. Here, the electronic structure of Ca5Ge3 (Cr5B3 type), which can be formulated (Ca+2)5(Ge2-6)Ge-4 in oxidation states, has been explored comparatively by means of semiempirical and first-principles density functional methods. The FP-APW calculations show that alkaline-earth-metal and germanium orbitals, particularly the d orbitals on the cations and the p-pi orbitals of the halogen-like dimeric Ge2-6, mix considerably to form a conduction band. This covalency perfectly explains the unusual metallic properties of the nominally electron-precise Zintl phase Ca5Ge3 and its numerous relatives. Similar calculational results are obtained for Sr5Ge3, Ba5Ge3, and Ca5Sn3. Cation d orbitals appear to be a common theme among Zintl phases that are also metallic.

Journal Article↗
PubMed2003

Valence compounds versus metals. Synthesis, characterization, and electronic structures of cubic Ae(4)Pn(3) phases in the systems Ae = Ca, Sr, Ba, Eu; Pn = As, Sb, Bi.

The isostructural compounds Sr(4)Bi(3), Ba(4)Bi(3), and Ba(4)As( approximately )(2.60) were prepared by direct reactions of the corresponding elements and their structures determined from single-crystal X-ray diffraction data as anti-Th(3)P(4) type in the cubic space group I43d, Z = 4 (a = 10.101(1) A, 10.550(1) A, 9.973 (1) A, respectively). The two bismuth compounds are stoichiometric, and the arsenide refines as Ba(4)As(2.60(2)). Only unrelated phases are obtained for all binary combinations among the title components for either Ca or Sb. The magnetic susceptibility and resistivities of Ba(4)Bi(3) and Eu(4)Bi(3) show that they are good metallic conductors ( approximately 40 microomega.cm at 298 K), whereas Ba(4)As(2.60) exhibits rho(150) > 1000 microomega.cm. The electronic structures of Sr(4)Bi(3), Ba(4)Bi(3), and Ba(4)As(3) were calculated by TB-LMTO-ASA methods. Mixing of cation d states into somewhat disperse valence p bands on Bi results in empty bands at E(F) and metallic behavior, whereas the narrower valence band in the electron-deficient Ba(4)As(3) leads to vacancies in about 11% of the anion sites and a valence compound.

Journal Article↗
PubMed2003

Nine hexagonal ca(5)pb(3)z phases in stuffed mn(5)si(3)-type structures with transition metal interstitial atoms z. Problems with classical valence States in possible zintl phases.

Ternary hexagonal Ae(5)Tt(3)Z phases have been obtained from high-temperature reactions (1000-1300 degrees C in Ta) only for Ae (alkaline-earth metal) = Ca, Tt (tetrel) = Pb, and Z = V, Cr, Mn, Fe, Co, Ni, Zn, Ru, or Cd. The hexagonal crystal structures (stuffed Mn(5)Si(3)-type, P6(3)/mcm, Z = 2) were refined for Z = Mn and Fe (a = 9.3580(3), 9.3554(5) A, c = 7.009(1), 7.009(1) A, respectively). In contrast, Ca(5)Pb(3)Z for Z = Cu or Ag form only with a trigonal structure (P3c1, Z = 2, a = 9.4130(3) A, c = 7.052(1) A for Cu) in which regular displacements of only the linear strings of Ca1 atoms occur. The existence of these compounds stands in contrast to the nonexistence of all binary Ae(5)Tt(3) products from Ca to Ba (Ae) and Si to Pb (Tt) with a Mn(5)Si(3)-type structure. Therefore, it once seemed attractive to consider the Z elements in these Ca(5)Pb(3)Z compounds as reducing agents (electron donors). The Mn and Fe structures appropriately exhibit greatly enlarged antiprismatic calcium cavities about Z. Other indications of relatively electron-poor environments around Fe are found in its properties, which include soft ferromagnetism with an elevated magnetic moment (6.3 micro(B)) and a large Fe 3p(3/2) binding energy relative to that in La(5)Ge(3)Fe, La(15)Ge(9)Fe, etc. The Ca(5)Pb(3)Mn phase exhibits metallic behavior (rho(295) = 135 microOmega cm) and temperature-independent Pauli paramagnetism. These properties are supported by ab initio band structure calculations for Ca(5)Pb(3)Mn, which show strong Ca-Pb bonding and a broad Pb-based band, with appreciable Ca-Mn and Ca-Pb bonding states at and above E(F). Distortion of the Cu analogue gives strengthened Ca-Pb bonding and reduced Cu-Ca1 repulsions. A Zintl phase description of these compounds and some related compounds in terms of closed Pb bands is not appropriate.

Journal Article↗