Stabilizing a metalloid {Zn12} unit within a polymetallide environment in [K2Zn20Bi16]6.

The access to molecules comprising direct Zn-Zn bonds has become very topical in recent years for various reasons. Low-valent organozinc compounds show remarkable reactivities, and larger Zn-Zn-bonded gas-phase species exhibit a very unusual coexistence of insulating and metallic properties. However, as Zn atoms do not show a high tendency to form clusters in condensed phases, synthetic approaches for generating purely inorganic metalloid Znx units under ambient conditions have been lacking so far. Here we show that the reaction of a highly reductive solid with the nominal composition K5Ga2Bi4 with ZnPh2 at room temperature yields the heterometallic cluster anion [K2Zn20Bi16]6-. A 24-atom polymetallide ring embeds a metalloid {Zn12} unit. Density functional theory calculations reveal multicenter bonding, an essentially zero-valent situation in the cluster center, and weak aromaticity. The heterometallic character, the notable electron-delocalization, and the uncommon nano-architecture points at a high potential for nano-heterocatalysis.

Synthesis and Crystal Structure of Dimorphic Dibenzo[cde,opq]rubicene.

Dibenzo[cde,opq]rubicene has been synthesized by an eight-step reaction sequence including an iron-mediated [2+2+1] cycloaddition and a flash vacuum pyrolysis as key steps. Two crystal modifications of the S-shaped, planar polycyclic aromatic hydrocarbon have been obtained and characterized by X-ray diffractometry.

Polybismuthide Anions as Ligands: The Homoleptic Complex [(Bi7 )Cd(Bi7 )]4- and the Ternary Cluster [(Bi6 )Zn3 (TlBi5 )]4.

We present the results from a reactivity study of the binary anion (TlBi3 )2- towards Group 12 metal compounds MPh2 (M=Zn, Cd, Hg) to gain access to coordination compounds of polycyclic polypnictide molecules such as Bi7 3- or Bi11 3- . The coordination chemistry of these polybismuthide cages has been unprecedented to date, while it has been known for a long time for the lighter Group 15 anions Pn7 3- (Pn=P, As, Sb). The use of (TlBi3 )2- , previously shown to release Tl under certain conditions in situ, resulted in the formation of the first heterometallic polyanion in which a nortricyclane-type polybismuthide coordinates a transition-metal atom, [(Bi7 )Cd(Bi7 )]4- . Reactions with the lighter Group 12 metal precursor yielded the uncommon ternary cluster [(Bi6 )Zn3 (TlBi5 )]4- , most likely representing a reaction intermediate, and at the same time hinting at the formation of the nortricyclane-shaped cage. Quantum-chemical studies provide deeper insight into the stability trends of the [(E7 )M(E7 )]4- anion family and reveal a complex bonding situation in [(Bi6 )Zn3 (TlBi5 )]4- , which features both localized and multi-center bonding.

The Identity of "Ternary" A/Tl/Pb or K/Tl/Bi Solid Mixtures and Binary Zintl Anions Isolated From Their Solutions.

Investigations of solid mixtures of the elemental combinations A/Tl/Pb (A=Na, K) and K/Tl/Bi indicate the presence of multiple binary and ternary Zintl phases, among them new ones containing Tl and Pb or Bi, respectively. Extractions with en/crypt-222 afford single crystals of several novel binary anions, including [Tl@Tl4 Pb8 ]4- and (Tl4 Bi3 )3- . [Tl@Tl4 Pb8 ]4- adopts a closo-type cage structure despite possessing one additional electron; it is therefore isostructural, yet not isoelectronic, with homoatomic [Tl@Tl12 ]11- obtained by solid state reactions. (Tl4 Bi3 )3- is a rare case of a pentagonal bipyramidal Zintl anion, yet the first binary one, and (unlike Tl77- ) the first one with a proper closo-type electron count. Assignment of the numbers and positions of the Tl/Pb or Tl/Bi atoms within the anionic clusters, indistinguishable in classical X-ray diffraction experiments, was achieved by means of quantum chemistry. The studies shed light on the complex situation in solid heavy element mixtures and their substantial differences from the composition of the Zintl anions obtained from them by extraction.

Between MOFs and molecules: organolead(IV) compounds with chain structures.

Organolead compounds are of interest mainly as catalysts and organolead halides have proved to be very efficient materials for solar cells. Two organolead(IV) dimethylarsinates, namely catena-poly[[triphenyllead(IV)]-µ-chlorido-[triphenyllead(IV)]-µ-dimethylarsinato-κ2O:O'], [Pb2(C6H5)6(C2H6AsO2)Cl]n or [(Ph3Pb)2Cl(O2AsMe2)], (1), and poly[chlorido(µ3-dimethylarsinato-κ3O:O,O':O')diphenyllead(IV)], [Pb(C6H5)2(C2H6AsO2)Cl]n or [(Ph2ClPb)(O2AsMe2)], (2), together with the triphenyllead(IV) diphenylphosphinate catena-poly[[triphenyllead(IV)]-µ-diphenylphosphinato-κ2O:O'], [Pb(C6H5)3(C12H10O2P)]n or [(Ph3Pb)(O2PPh2)], (3), have been synthesized and characterized by single-crystal X-ray diffraction, IR spectroscopy and mass spectrometry. In (1), a chain structure was found with alternating chloride and Pb-O-As-O-Pb arsinate bridges between five-coordinate PbIV atoms. In (2), bidentate and chelate-like bonded dimethylarsinate ligands form double chains with heptacoordinated PbIV atoms. In (3), a pentacoordinated PbIV atom is connected by Pb-O-P-O-Pb phosphinate bridges to form a linear chain. Obviously, the steric demand of the phenyl ligands at PbIV reduces the possibility of interconnections via polydentate ligands to one dimension only. Thus, no metal-organic frameworks (MOF) are formed but instead various chain structures are observed.

Main Group Metal-Actinide Magnetic Coupling and Structural Response Upon U(4+) Inclusion Into Bi, Tl/Bi, or Pb/Bi Cages.

The encapsulation of actinide ions in intermetalloid clusters has long been proposed but was never realized synthetically. We report the isolation and experimental, as well as quantum chemical, characterization of the uranium-centered clusters [U@Bi12](3-), [U@Tl2Bi11](3-), [U@Pb7Bi7](3-), and [U@Pb4Bi9](3-), upon reaction of (EE'Bi2)(2-) (E = Ga, Tl, E' = Bi; E = E' = Pb) and [U(C5Me4H)3] or [U(C5Me4H)3Cl] in 1,2-diaminoethane. For [U@Bi12](3-), magnetic susceptibility measurements rationalize an unprecedented antiferromagnetic coupling between a magnetic U(4+) site and a unique radical Bi12(7-) shell.

Understanding of multimetallic cluster growth.

The elucidation of formation mechanisms is mandatory for understanding and planning of synthetic routes. For (bio-)organic and organometallic compounds, this has long been realized even for very complicated molecules, whereas the formation of ligand-free inorganic molecules has widely remained a black box to date. This is due to poor structural relationships between reactants and products and the lack of structurally related intermediates--due to the comparably high coordination flexibility of involved atoms. Here we report on investigations of the stepwise formation of multimetallic clusters, based on a series of crystal structures and complementary quantum-chemical studies of (Ge2As2)(2-), (Ge7As2)(2-), [Ta@Ge6As4](3-), [Ta@Ge8As4](3-) and [Ta@Ge8As6](3-). The study makes use of efficient quantum-chemical tools, enabling the first detailed screening of the energy hypersurface along the formation of ligand-free inorganic species for a semi-quantitative picture. The results can be generalized for an entire family of multimetallic clusters.

Two-dimensional zeolite-like network in the new caesium copper aluminate Cs2CuAl4O8.

Monoclinic dicaesium copper tetraaluminate, Cs2CuAl4O8, space group P2(1)/c, a = 8.4551 (7), b = 10.012 (1), c = 17.073 (2) Å, ß = 101.643 (9)°, Z = 6, was obtained by high-temperature crystallization from a phosphate flux. Its microporous crystal structure presents the first example of double layers built from [AlO4] tetrahedra combined in 4-, 6- and 8-rings, topologically similar to those found in the ATT-type zeolites and isostructural minerals armstrongite, davanite and dalyite. These layers show a rare arrangement of three [AlO4] tetrahedra sharing one oxygen vertex. The aluminate slabs are further linked by chains of edge-sharing [CuO4] square planes to form a mixed anionic three-dimensional framework with Cs(+) cations in channels and cavities. An unusually short Cu···Cs distance of 3.166 Šis ascribed to the strong Jahn-Teller effect of Cu(2+). The magnetic subsystem demonstrates properties of an alternating antiferromagnetic chain with a gap in the spectrum of magnetic excitations.

[V@Ge8As4]3- and [Nb@Ge8As6]3-: encapsulation of electron-poor transition metal atoms.

[K([2.2.2]crypt)](+) salts of [V@Ge8As4](3-) and [Nb@Ge8As6](3-) were obtained by extraction of quaternary phases with en/[2.2.2]crypt. The V-Ge-As anion is the first Zintl anion incorporating a (formal) V(5+) cation, thus the smallest cation ever embedded within a main group (semi-)metal cage. It represents the second example of a novel 12-vertex cluster architecture. The bonding situation was elucidated by quantum chemistry, also allowing for a precise assignment of Ge vs. As atoms, being indistinguishable by X-ray diffraction.

Ionic-radius-driven selection of the main-group-metal cage for intermetalloid clusters [Ln@Pbx Bi14-x](q-) and [Ln@Pby Bi13-y](q-) (x/q=7/4, 6/3; y/q=4/4, 3/3).

Reactions of the binary, pseudo-homoatomic Zintl anion (Pb2 Bi2 )(2-) with Ln(C5 Me4 H)3 (Ln=La, Ce, Nd, Gd, Sm, Tb) in the presence of [2.2.2]crypt in ethane-1,2-diamine/toluene yielded ten [K([2.2.2]crypt)](+) salts of lanthanide-doped semimetal clusters with 13 or 14 surface atoms. Single-crystal X-ray diffraction and energy-dispersive X-ray spectroscopy indicated the presence of the anions [Ln@Pb6 Bi8 ](3-), [Ln@Pb3 Bi10 ](3-), [Ln@Pb7 Bi7 ](4-), or [Ln@Pb4 Bi9 ](4-) in single or double salts; the latter showed various ratios of the components in the solid state. The anions are the first ternary intermetalloid clusters comprising only elements of the sixth period of the periodic table, namely, Pb, Bi and lanthanides. This study, which was complemented by ESI mass spectrometry and (139) La NMR spectroscopy in solution, rationalizes a continuous development of the ratio of 13:14-atom cages with the ionic radius of the embedded Ln(3+) ion, which seems to select the most suitable cage type. Quantum chemical investigations helped to analyze this situation in more detail and to explain the observed subtle influence of the atomic radii. Magnetic measurements confirmed that the embedded Ln(3+) ions keep their expected paramagnetic or diamagnetic nature.

Unusual 14-electron fragments [Pd(η(3) -Bi3-x Pbx )]((x+1)-) as pseudo lead atoms in closo-[Pd@Pd2 Pb10 Bi6 ](4-).

How to simplify a complex thing: A salt of the heaviest intermetalloid cluster known to date, [K([2.2.2]crypt)]4 [Pd@Pd2 Pb10 Bi6 ]⋅2 en, resulted from a reaction of [Pd(PPh3 )4 ] with [K([2.2.2]crypt)]2 (Pb2 Bi2 )⋅2 en in ethane-1,2-diamine (en). The electron number of the ternary intermetalloid anion accords with Wade-Mingos rules, as the [Pd(η(3) -Bi3-x Pbx )]((x+1)-) (x=0, 1) 14-electron fragments formed in situ are isolobal with Pb atoms.

Changes in the structural dimensionality of selenidostannates in ionic liquids: formation, structures, stability, and photoconductivity.

In situ transformations of selenidostannate frameworks in ionic liquids (ILs) were initiated by treatment of the starting phase K2[Sn2Se5] and the consecutive reaction products by means of temperature increase and/or amine addition. Along the reaction pathway, the framework dimensionalities of the five involved selenidostannate anions develop from 3D to 1D and back, both in top-down and bottom-up style. Addition of ethane-1,2-diamine (en) led to the reversion of the 2D→1D step from 2D-{[Sn24Se56](16-)} to 1D-{[Sn6Se14](4-)}. As rationalized by DFT investigations, the 2D anion is thermodynamically favored. Photoconductivity measurements reveal that all samples show Schottky contact behavior with absolute thresholds below 10 V. One of the samples exhibits conductive states within the energy range of visible photons.

Controlling the assembly of chalcogenide anions in ionic liquids: from binary Ge/Se through ternary Ge/Sn/Se to binary Sn/Se frameworks.

Seven compounds with binary or ternary Ge/Se, Ge/Sn/Se, or Sn/Se anionic substructures crystallized upon the ionothermal reactions of [K(4)(H(2)O)(3)][Ge(4)Se(10)] with SnCl(4)·5H(2)O or SnCl(2) in [BMMIm][BF(4)] or [BMIm][BF(4)] (BMMIm=1-butyl-2,3-dimethyl-imidazolium, BMIm=1-butyl-3-methyl-imidazolium). The products were obtained by subtly varying the reaction conditions; the nature and amount of an additional amine was the most important parameter in the product selection and in determining the Sn/Ge ratio in the isolated products. The crystal structures of these chalcogenides were based on complex anions with unprecedented topologies that varied from discrete clusters (0D) through 1D chain structures or 2D layers to 3D frameworks. The architecture and composition of the title compounds were well reflected by their optical absorption behavior. Herein, we report a convenient approach for the generation of chalcogenidometallate phases with fine-tunable electronic properties in ionic liquids, which have been inaccessible by traditional methods.

"Zeoball" [Sn36Ge24Se132]24-: a molecular anion with zeolite-related composition and spherical shape.

Ionothermal reactions of [Ge(4)Se(10)](4-) with SnCl(4)·5H(2)O yielded [BMMIm](24)[Sn(36)Ge(24)Se(132)] (ZBT-1) and [BMIm](24)[Sn(32.5)Ge(27.5)Se(132)] [ZBT-2; B(M)MIm = 1-butyl-(2,)3-(di)methylimidazolium]. These contain the largest known discrete polyanion consisting only of main-group elements. In spite of a zeolite-related composition, the 192-atom "zeoball" anion adopts a spherical shape, which has been unprecedented in the chemistry of zeolites and their homologues and relatives. Preliminary studies indicated that ZBT-1 traps I(2) molecules and induces heterolytic I-I bond cleavage.

(2E,6E)-2,6-Bis(4-methyl-benzyl-idene)cyclo-hex-3-en-1-one.

The title compound, C(22)H(20)O, shows an approximately planar cyclo-hexenone ring [maximum deviation = 0.069 (4) Å], with a disordered position of the C=C bond [ratio = 0.71 (2)/0.29 (2)]. The benzene rings of the 4-methyl-benzyl-idene units, attached in the 2- and 6-positions to the cyclo-hexenone ring, are rotated in the same direction by 28.6 (4) and 22.4 (4)°, with respect to the mean plane of the cyclo-hexenone ring [fraction 0.71 (2); maximum deviation = 0.06 (3) Å]. In the crystal, mol-ecules are packed in the manner of a distorted hexa-gonal rod packing with their long axes all aligned along [201]. A number of C-H⋯π inter-actions stablize the crystal structure.

(4Z,6Z)-4,6-Bis(4-meth-oxy-benzyl-idene)-2,2-dimethyl-1,3-dioxan-5-one.

The title compound, C(22)H(22)O(5), crystallizes with two independent mol-ecules in the asymmetric unit, both of which possess pseudo-C(s) symmetry. The central 1,3-dioxanone rings have envelope conformations, with the C atom bearing the two methyl groups at the flap. The benzene rings of the meth-oxy-benzyl-idene units, attached in the 4- and 6-positions on the central 1,3-dioxanone rings, are tilted in the same direction with dihedral angles varying between 8.2 (1) and 18.1 (1)°. The crystal packing is influenced by π-stacking inter-actions of the parallel displaced type [centroid-centroid distance of 3.723 (1) Šfor mol-ecule 1 and 3.884 (1) Šfor mol-ecule 2, with ring slippages of 1.432 and 1.613 Å, respectively] and the T-shaped type, with the long mol-ecular axes all aligned along [010].

Switching the reactivity of dihydrothiopyran-4-one with aldehydes by aqueous organocatalysis: Baylis-Hillman, aldol, or aldol condensation reactions.

An aqueous medium containing catalytic amounts of a tertiary amine was employed to direct the chemoselectivity of the reaction of aldehydes with 1a. With DBU, 2 was formed at room temperature as a rare exemplary of Baylis-Hillman reactions in heterocyclic enones. DABCO alternated the pathway toward an aldol reaction to form syn/anti mixtures of 3 with the syn isomers being the major products. With Et(3)N, aldol condensation dominated.

Presence or absence of a central Se atom in silver selenide/selenolate clusters with halite topology: syntheses and properties of [(Ph(3)PAg)(8)Ag(6)(mu(6)-Se)(1-x/2)(SePh)(12)](x+) (x = 0, 1).

Two types of Ph(3)P/Ph ligated Ag(14)Se(13-x) (x = 0, 0.5) clusters with halite topology were synthesized that differ by the occupation/nonoccupation of the central position by a 13th Se atom and the resulting charge: neutral [(Ph(3)PAg)(8)Ag(6)(mu(6)-Se)(SePh)(12)].11THF (1) and ionic [(Ph(3)PAg)(8)Ag(6)(mu(6)-Se)(0.5)(SePh)(12)][R(3)SnCl(2)].nTHF (R = Ph, n = 6 (2a); Cy, n = 5 (2b)) are all based on a tetradecanuclear cluster. The structural response on the charge was rationalized by DFT calculations, and the optical absorption behavior was studied.

12-Membered borophosphate rings in KNi5[P6B6O23(OH)13].

The title compound, potassium pentanickel hexaborophosphate tridecahydroxide, was synthesized under hydrothermal conditions from the NiCl(2)-K(3)PO(4)-B(2)O(3)-K(2)CO(3)-H(2)O system. The crystal structure was determined using single-crystal X-ray diffraction at 100 K. The KNi(5)[P(6)B(6)O(23)(OH)(13)] phase is cubic. For the three crystallographically distinct Ni centers, two occupy sites with 3 symmetry, while the third Ni and the K atom are located on 3 sites. The structure is built from alternating borate and phosphate tetrahedra forming 12-membered puckered rings with K(+) ions at the centers. These rings are arranged as in cubic dense sphere packing. A novel feature of the new crystal structure is the presence of linear trimers of face-sharing [NiO(6)] octahedra occupying the octahedral interstices of this sphere packing, and of single [NiO(6)] octahedra in the tetrahedral interstices. All oxygen corners of the Ni octahedra are linked to phosphate or borate tetrahedra of the 12-membered rings to form a mixed anionic framework.

Detailed spectroscopic, thermodynamic, and kinetic studies on the protolytic equilibria of Fe(III)cydta and the activation of hydrogen peroxide.

The crystal structure of the as-yet-unknown salt K[Fe(III)(cydta)(H(2)O)].3H(2)O, where cydta = (+/-)-trans-1,2-cyclohexanediaminetetraacetate, has been resolved: orthorhombic space group Pbca with R1 = 0.0309, wR2 = 0.0700, and GOF = 0.99. There are two independent [Fe(III)(cydta)(H(2)O)](-) anions in the asymmetric unit, and the ligand is (R,R)-cydta in both cases. The coordination polyhedron is a seven-coordinate capped trigonal prism where the quadrilateral face formed by the four ligand donor oxygen atoms is capped by the coordinated water molecule. The speciation of [Fe(III)(cydta)(H(2)O)](-) in water was studied in detail by a combination of techniques: (i) Measurements of the pH dependence of the Fe(III/II)cydta redox potentials by cyclic voltammetry enabled the estimation of the stability constants (0.1 M KNO(3), 25 degrees C) of [Fe(III)(cydta)(H(2)O)](-) (log beta(III)(110) = 29.05 +/- 0.01) and [Fe(II)(cydta)(H(2)O)](2-) (log beta(II)(110) = 17.96 +/- 0.01) as well as pK(III)(a1OH) = 9.57 and pK(II)(a1H) = 2.69. The formation enthalpy of [Fe(III)(cydta)(H(2)O)](-) (DeltaH degrees = -23 +/- 1 kJ mol(-1)) was measured by direct calorimetry and is compared to the corresponding value for [Fe(III)(edta)(H(2)O)](-) (DeltaH degrees = -31 +/- 1 kJ mol(-1)). (ii) pH-dependent spectrophotometric titrations of Fe(III)cydta lead to pK(III)(a1OH) = 9.54 +/- 0.01 for deprotonation of the coordinated water and a dimerization constant of log K(d) = 1.07. These data are compared with those of Fe(III)pdta (pdta = 1,2-propanediaminetetraacetate; pK(III)(a1OH) = 7.70 +/- 0.01, log K(d) = 2.28) and Fe(III)edta (pK(III)(a1OH) = 7.52 +/- 0.01, log K(d) = 2.64). Temperature- and pressure-dependent (17)O NMR measurements lead to the following kinetic parameters for the water-exchange reaction at [Fe(III)(cydta)(H(2)O)](-) (at 298 K): k(ex) = (1.7 +/- 0.2) x 10(7) s(-1), DeltaH(++) = 40.2 +/- 1.3 kJ mol(-1), DeltaS(++) = +28.4 +/- 4.7 J mol(-1) K(-1), and DeltaV(++) = +2.3 +/- 0.1 cm(3) mol(-1). A detailed kinetic study of the effect of the buffer, temperature, and pressure on the reaction of hydrogen peroxide with [Fe(III)(cydta)(H(2)O)](-) was performed using stopped-flow techniques. The reaction was found to consist of two steps and resulted in the formation of a purple Fe(III) side-on-bound peroxo complex [Fe(III)(cydta)(eta(2)-O(2))](3-). The peroxo complex and its degradation products were characterized using Mossbauer spectroscopy. Formation of the purple peroxo complex is only observable above a pH of 9.5. Both reaction steps are affected by specific and general acid catalysis. Two different buffer systems were used to clarify the role of general acid catalysis in these reactions. Mechanistic descriptions and a comparison between the edta and cydta systems are presented. The first reaction step reveals an element of reversibility, which is evident over the whole studied pH range. The positive volume of activation for the forward reaction and the positive entropy of activation for the backward reaction suggest a dissociative interchange mechanism for the reversible end-on binding of hydrogen peroxide to [Fe(III)(cydta)(H(2)O)](-). Deprotonation of the end-on-bound hydroperoxo complex leads to the formation of a seven-coordinate side-on-bound peroxo complex [Fe(III)(cydta)(eta(2)-O(2))](3-), where one carboxylate arm is detached. [Fe(III)(cydta)(eta(2)-O(2))](3-) can be reached by two different pathways, of which one is catalyzed by a base and the other by deprotonated hydrogen peroxide. For both pathways, a small negative volume and entropy of activation was observed, suggesting an associative interchange mechanism for the ring-closure step to the side-on-bound peroxo complex. For the second reaction step, no element of reversibility was found.