Alexander V. Virovets

A Novel Framework Type for Inorganic Clusters with Cyanide Ligands: Crystal Structures of Cs2Mn3[Re6Se8(CN)6]2⋅15 H2O and (H3O)2Co3[Re6Se8(CN)6]2⋅14.5 H2O

Large cavities occupied by cations and water molecules are part of the polymeric inorganic cluster structure made up of [Re6Se8(CN)6]4− and M2+ ions (M=Mn, Co; see structure on the right). Remarkably, the water molecules play an essential role in the stabilization of the structure: When the cluster is heated to 80–160°C, water is lost irreversibly, and a sharp change in structure is observed.

Pentaphosphaferrocene as a Linking Unit for the Formation of One‐ and Two‐Dimensional Polymers

Different copper halide, different copper product: The cyclo-P5-ligand complex [Cp*Fe(5-P5)] (1; Cp*=C5Me5) reacts with CuBr and CuI to give two-dimensional networks in which 1 is the linking unit. However, a novel one-dimensional-chain coordination polymer (see picture) is formed with CuCl.

A Spherical Molecule with a Carbon‐Free Ih‐C80 Topological Framework

The complete encapsulation of ortho-carborane by a fullerene-like building-block system consisting of pentaphosphaferrocene and Cu(I)Cl leads to the formation of the spherical supermolecule C(2)B(10)H(12) section sign[{Cp*Fe(eta(5)-P(5))}(12)(CuCl)(20)]. This product of template-controlled aggregation represents the first example of a carbon-free C(80) analogue possessing icosahedral symmetry.

Pentaphosphaferrocen als verknüpfende Einheit in ein‐ und zweidimensionalen Polymeren

Unterschiedliche Produkte mit unterschiedlichen Kupferhalogeniden: Der cyclo-P5-Ligandkomplex [Cp*Fe(5-P5)] 1 bildet bei der Reaktion mit CuBr und CuI zweidimensionale Netzwerke mit 1 als verknupfender Einheit, wahrend mit CuCl ein Koordinationspolymer mit eindimensionaler Kettenstruktur entsteht (siehe Bild).

Structures and Properties of Spherical 90-Vertex Fullerene-Like Nanoballs

By applying the proper stoichiometry of 1:2 to [Cp(R)Fe(eta(5)-P(5))] and CuX (X=Cl, Br) and dilution conditions in mixtures of CH(3)CN and solvents like CH(2)Cl(2), 1,2-Cl(2)C(6)H(4), toluene, and THF, nine spherical giant molecules having the simplified general formula [Cp(R)Fe(eta(5)-P(5))]@[{Cp(R)Fe(eta(5)-P(5))}(12){CuX}(25)(CH(3)CN)(10)] (Cp(R)=eta(5)-C(5)Me(5) (Cp*); eta(5)-C(5)Me(4)Et (Cp(Et)); X=Cl, Br) have been synthesized and structurally characterized. The products consist of 90-vertex frameworks consisting of non-carbon atoms and forming fullerene-like structural motifs. Besides the mostly neutral products, some charged derivatives have been isolated. These spherical giant molecules show an outer diameter of 2.24 (X=Cl) to 2.26 nm (X=Br) and have inner cavities of 1.28 (X=Cl) and 1.20 nm (X=Br) in size. In most instances the inner voids of these nanoballs encapsulate one molecule of [Cp*Fe(eta(5)-P(5))], which reveals preferred orientations of pi-pi stacking between the cyclo-P(5) rings of the guest and those of the host molecules. Moreover, pi-pi and sigma-pi interactions are also found in the packing motifs of the balls in the crystal lattice. Electrochemical investigations of these soluble molecules reveal one irreversible multi-electron oxidation at E(p)=0.615 V and two reduction steps (-1.10 and -2.0 V), the first of which corresponds to about 12 electrons. Density functional calculations reveal that during oxidation and reduction the electrons are withdrawn or added to the surface of the spherical nanomolecules, and no Cu(2+) species are involved.

Cucurbituril as a New Macrocyclic Ligand for Complexation of Lanthanide Cations in Aqueous Solutions

(Aqua)lanthanide complexes with cucurbituril {[Gd(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (1), {[Gd(NO3)(C2H5OH)(H2O)3](C36H36N24O12)}(NO3)2·5.5H2O (2), {[Ho(NO3)(H2O)4](C36H36N24O12)}(NO3)2·7H2O (3), {[Yb(NO3)(H2O)4](C36H36N24O12)}(NO3)2·6H2O (4), {[La(H2O)6(SO4)](C36H36N24O12)}(NO3)·12H2O (5), {[Gd(H2O)4]2(C36H36N24O12)3}Br6·45H2O (6), and {[Ce(H2O)5]2(C36H36N24O12)2}Br6·26H2O (7) were obtained in high yield by reaction of cucurbituril with aqueous solutions of lanthanide(III) species. The crystal structures of the compounds show a packing of 1:1, 2:2, and 2:3 in the (cucurbituril)lanthanide complexes in which cucurbituril plays a bidentate ligand role, and water molecules of the (aqua)lanthanide complexes form hydrogen bonds with carbonyl groups of the cucurbituril molecule. The guest water molecule is situated in the cucurbituril molecule cavity of 2 and 5. The crystal structure of 6 is a packing of three-deck sandwiches, built from alternating cucurbituril molecules and Gd(H2O)43+ ions. The largest distance between outermost oxygen atoms in the sandwiches is 30.04 A. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Stabilization of Tetrahedral P4 and As4 Molecules as Guests in Polymeric and Spherical Environments

Chemistry as a science has originated from the exploration and handling of native elements such as sulfur or noble metals that allowed the formulation of the crucial concept of a chemical element. Despite great achievements of inorganic chemistry in the last century, the structural features of some simple substances are still not explicitly clear. It is remarkable that modern X-ray crystallography succeeded in crystal structure determination of proteins containing several thousands of atoms, yet it still faces obstacles in the characterization of some elementary compounds. For example, the extremely high aggressiveness of fluorine gas that was discovered in 1886 impeded its structural characterization for 78 years. Another barrier is the instability and chemical reactivity of allotropic modifications such as O3, whose crystal structure was not revealed until 2001, or the molecular allotropes of phosphorus and arsenic. The high dynamic motion of tetrahedral P4 molecules in white phosphorus led to a complete disorder of the cubic a-P4 phase under ambient conditions. To overcome this problem and obtain a convincing X-ray structural determination, single crystals of the ordered b-P4 phase have to be grown at temperatures below 77 8C. Arsenic exists in three allotropic modifications of which yellow arsenic, consisting of As4 tetrahedral molecules, is the most toxic and the least stable one. It can be obtained in a time-consuming synthesis by heating gray arsenic to 750 8C. The emerging As4 is taken away by a constant flow of a carrier gas and can be discharged into a hot solvent. In contrast to white phosphorus, yellow arsenic cannot be stored as a solid. It is surprisingly poorly soluble in common organic solvents, and it readily polymerizes under ambient conditions to gray arsenic, especially when exposed to light or X-rays. Hence, until now no solid-state structure of yellow arsenic is known. Moreover, traces of gray arsenic accelerate the polymerization of As4 even in solution. Yet, only scarce facts regarding its reactivity or coordination behavior are known. One of the ways to stabilize such unstable molecules is to include them as a guest in a molecular container or polymeric matrix. Oxidation of P4 in air was shown to be prevented by inclusion into the cavity of a supramolecular arrangement of a tetranuclear iron complex. Moreover, the co-crystallization of P4 in the lattice of solid C60 was reported. [8] Recently, Fujita et al. presented an elegant method for the X-ray structural characterization of organic compounds, only available in nanogram scale, based on their inclusion into singlecrystalline, porous 3D coordination polymers. Furthermore, our group succeeded in the stabilization of the unstable paramagnetic 16-electron complex, [Cp*Cr(h-As5)], embedded as a guest in the giant [Cu20Cl20{Cp*Fe(h -P5)}12] molecule (Cp* = h-C5Me5). [10] We reasoned that the use of host molecules could not only enhance the stability of the E4 (E = P, As) molecules, especially of As4, but would also decrease their molecular motion in the solid state. We have reported that the system [Cp*Fe(h-P5)] and Cu -halides forms either polymeric structures or large fullerene-like spherical molecules capable of encapsulating guest molecules and, thus perhaps, the E4 tetrahedra themselves. Herein we present the synthesis and X-ray molecular and crystal structure of polymeric host compounds that contain intact E4 tetrahedra as guests. Furthermore we show that [Ag(h-As4)2] [pftb] (pftb = {Al(OC(CF3)3)4}) [5e] can be utilized for the release of As4 as remarkably light-stable and highly concentrated solutions, making it an ideal storage medium for yellow arsenic. Finally these As4 solutions, as well as solutions of P4, were used to build up spherical macromolecules containing intact E4 tetrahedra as guest molecules. In the presence of P4 or As4, the reaction of CuCl with [Cp*Fe(h-P5)] leads to the formation of the isostructural compounds [Cu2Cl2{Cp*Fe(h -P5)}2]1·(P4)n (1) and [Cu2Cl2{Cp*Fe(h-P5)}2]1·(0.75As4)n (2), in which the tetrahedral voids are filled by perfectly adjusted E4 molecules. Surprisingly, the crystals of 1 and 2 are lightand air-stable for days and are insoluble in common solvents. Crystal-structure analysis reveals that in 1 all the voids are totally occupied by P4, while in 2 the As4 molecules statistically occupy 75 % of the available sites (Figure 1) probably a result of the low and rapidly decreasing concentration of As4 in the reaction medium. The E4 tetrahedra are fixed between the polymeric chains by four pairs of E···P(P5) intermolecular contacts of 3.98 and 4.00 in 1 and 3.98 and 4.04 in 2 (Figure 1), together with [*] Dr. C. Schwarzmaier, Dr. A. Schindler, C. Heindl, S. Scheuermayer, Dr. M. Neumeier, Prof. Dr. R. Gschwind, Prof. Dr. M. Scheer Universit t Regensburg 93040 Regensburg (Germany) E-mail: Manfred.Scheer@chemie.uni-regensburg.de

Octahedral rhenium(III) chalcocyanide cluster anions: Synthesis, structure, and solid state design

The review summarizes data on synthesis and structure of rhenium chalcocyanide cluster onions [ Re6X8(CN)6]4-f (X = S, Se, Te) belonging to a new class of inorganic compounds. Two main groups of such compounds are considered: salts with an island structure and polymer compounds. Various factors governing the type of structure and the dimensionality of the polymer compounds are analyzed, including the nature of the chalcogen atom in the cluster anion, preferable coordination of the transition metal cation, and the size of additional charge-compensating cations. Crystal-chemical approaches to design of complex salts based on octahedral rhenium chalcocyanide cluster anions are formulated.

Synthesis and crystal structure of a hexanuclear rhenium cluster complex Cs3K[Re6(μ3-S)6 (μ3-Te0.66S0.34)2(CN)6]. Cationic control over orientation of the cluster anion

Abstract The hexanuclear complex rhenium salt Cs3K[Re6(μ3-S)6(μ3-Te0.66S0.34)2(CN)6] ({Bd1}) has been prepared by the reaction of Re6Te15 with molten KSCN and subsequent treatment with an aqueous solution of CsCl. Its crystal structure has been determined by X-ray structural analysis. The anion has the site symmetry 3 . The Re6 octahedron is coordinated to six μ3-S and two trans mixed μ3-X ligands of the refined composition 66(3)%Te+34(3)%S. In addition there are six almost linear terminal CN ligands in its environment. The ReRe distances [2.630(2) A] in the Re3 faces capped by the μ3-X ligands are significantly longer than those in the faces capped by the μ3-S ligands [2.615(2) A].

Topological Motifs in Cyanometallates: From Building Units to Three-Periodic Frameworks

This review focuses on topological features of three-periodic (framework) p, d, and f metal cyano complexes or cyanometallates, i.e. coordination compounds, where CN(-) ligands play the main structure-forming role. In addition, molecular, one-periodic (chain), and two-periodic (layer) cyanometallates are considered as possible building blocks of the three-periodic cyanometallates. All cyanometallates are treated as systems of nodes (mononuclear, polynuclear, or transitional metal cluster complexes) joined together via CN-containing spacers. The most typical nodes and spacers as well as methods of their connection are described and systematized. Particular attention is paid to the overall structural motifs in the three-periodic cyanometallates, especially to the relations between the local coordination (coordination figure) of structural units and the entire framework topology. The chemical factors are discussed that influence the cyanometallate topological properties due to modification of nodes, spacers, or coordination figures.