Rationally functionalized deltahedral zintl ions: synthesis and characterization of [Ge9-ER3]3-, [R3E-Ge9-ER3]2-, and [R3E-Ge9-Ge9-ER3]4- (E=Ge, Sn; R=Me, Ph)

Six new derivatized deltahedral Zintl ions have been synthesized by reactions between the known Zintl ions Ge(9) (n-) with the halides R(3)EX and/or the corresponding anions R(3)E(-) for E=Ge or Sn. This rational approach is based on our previous discovery that these derivatization reactions are based on nucleophilic addition to the clusters. All species were structurally characterized as their salts with potassium countercations sequestered in 2,2,2-crypt or [18]crown-6 ether. The tin-containing anions were characterized also in solutions by (119)Sn NMR spectroscopy. The reaction types for such substitutions and the structures of the new anions are discussed.     

New Molecular Cage Clusters of Pb by Encapsulation of Mg

Endohedral clusters formed from the Zintl ions Pb₁₀^2? and Pb₁₂^2? are particularly stable and therefore suitable for the assembly of larger aggregates. We therefore investigate the formation of Mg‐doped lead clusters in the gas phase, and demonstrate that a whole series of new molecular cage clusters of lead can be generated by encapsulation of magnesium. Mass spectrometry reveals that some of the cluster compounds, with one and two Mg atoms attached to the lead clusters, display large intensities compared to the pure lead clusters, which indicates that the compound clusters are particularly stable. The magnesium‐doped lead‐cluster assemblies were further analyzed within a molecular‐beam electric deflection experiment. Almost vanishing permanent dipole moments for MgPb_10–16 support the idea that a single Mg atom could be encapsulated within a highly symmetric lead cage, which results in structures with not only enhanced stability but also increased symmetry compared to the pure lead clusters Pb_N.     

[(Me3Si)Si]3EtGe9Pd(PPh3), a Pentafunctionalized Deltahedral Zintl Cluster: Synthesis,Structure, and Solution Dynamics

The title compound, which has a ten‐atom deltahedral cluster core of Ge₉Pd, was synthesized through insertion of Pd(PPh₃) into the tetrasubstituted nona‐germanium cluster [(Me₃Si)Si]₃EtGe₉ through a reaction of the latter with Pd(PPh₃)₄. This first reaction of neutral tetrasubstituted nine‐atom clusters shows that they retain reactivity despite their neutral charge. The Ge₉Pd core is the first that incorporates a 5‐connected transition metal other than from Group VI, a noble metal in this case. Single‐crystal X‐ray diffraction shows that the ten‐atom core is a closo‐cluster with the expected shape of a bicapped square antiprism. ¹H and ¹³C NMR spectroscopy show that, in contrast to the parent tetra‐substituted [(Me₃Si)Si]₃EtGe₉, the new compound does not exhibit dynamics. Relativistic DFT calculations are used to explain the differences.     

On the Formation of Intermetalloid Clusters: Titanocene(III)diammin as a Versatile Reactant Toward Nonastannide Zintl Clusters

The reactivity of TiCp₂Cl₂ (d⁰) towards Zintl clusters was studied in liquid ammonia (Cp=cyclopentadienyl). Reduction of Ti^IVCp₂Cl₂ and ligand exchange led to the formation of [Ti^IIICp₂(NH₃)₂]⁺, also obtainable by recrystallization of [CpTi^IIICl]₂. Upon reaction with [K₄Sn₉], ligand exchange leads to [TiCp₂(η¹‐Sn₉)(NH₃)]^3?. A small variation of the stoichiometry led to the formation of [Ti(η⁴‐Sn₈)Cp]^3?, which cocrystallizes with [TiCp₂(NH₃)₂]⁺ and [TiCp₂(η¹‐Sn₉)(NH₃)]^3?. Finally, the large intermetalloid cluster anion [Ti₄Sn₁₅Cp₅]^n? (n=4 or 5) was obtained from the reaction of K₁₂Sn₁₇ and TiCp₂Cl₂ in liquid ammonia. The isolation of three side products, [K([18]crown‐6)]Cp, [K([18]crown‐6)]Cp(NH₃), and [K([2.2]crypt)]Cp, suggests a stepwise elimination of the Cl^? and Cp^? ligands from TiCp₂Cl₂ and thus gives a hint to the mechanism of the product formation in which [Ti(η⁴⁺²‐Sn₈)Cp]^3? has a key role.     

Reactions of exo-substituted RSn9(3-) clusters with Pd: endohedral cluster formation and oxidative insertion

Pyridine/ethylenediamine solutions of [Sn(9)SnCy(3)](3-) (1) react with [Pd(PPh(3))(4)] to give new clusters [Pd@Sn(9)SnCy(3)](3-) (2) and [Pd@Sn(9)PdSnCy(3)](3-) (3), depending on stoichiometry. These compounds are formed sequentially and are the first transition metal derivates of exo-substituted Zintl clusters. Oxidative insertion of a Pd atom into the Pd@Sn(9)-SnCy(3) bond of 2 to form 3 represents a new reaction type for Zintl cluster compounds. The conversion Sn(9)(4-)→1→2→3 is a rare case in which charge and mass are conserved in a series of Zintl clusters. Complexes 1, 2, and 3 are all highly fluxional in solution. In all three clusters, the nine Sn vertices are in rapid exchange on the NMR timescale. In 1 and 2, the exo-SnCy(3) substituent also scrambles intramolecularly around the outside of the clusters. In 3, the SnCy(3) group remains attached to the vertex Pd atom. The disparate reactions with the other RSn(9)(3-) ions are discussed.     

The closo-Pb10(2-) Zintl ion in the [Ni@Pb10]2- cluster

The cluster [Ni@Pb10](2-), prepared from Pb9(4-) and Ni(COD)2, contains a new Zintl ion subunit, closo-Pb10(2-), centered by a Ni atom.     

Tetrahedral [Tt4]4– Zintl Anions Through Solution Chemistry: Syntheses and Crystal Structures of the Ammoniates Rb4Sn4·2NH3, Cs4Sn4·2NH3, and Rb4Pb4·2NH3

The crystalline isotypic solvates Rb₄Sn₄·2NH₃, Cs₄Sn₄·2NH₃, and Rb₄Pb₄·2NH₃ have been synthesized using the direct reduction of elemental tin or tetraphenyltin, respectively, with heavier alkali metals or the dissolution of the binary phase RbPb in liquid ammonia. These compounds contain the cluster ions [Sn₄]^4– or [Pb₄]^4– respectively. This is the first time that[Tt₄]^4– ions (Tt = tetrels) are detected as result of a solution reaction. The accommodation of the ammonia molecules, which build up ion‐dipole interactions to alkali metal cations, requires some modifications of the crystal structures compared to the binary phases RbSn, CsSn, and RbPb. The tetrahedral [Tt₄]^4– anions have a slightly lower coordination by Rb⁺ or Cs⁺ cations and, furthermore, the intercluster distances show a remarkable increase.     

[{(CO)5Cr}6Ge6]2−, A Molecular Organometallic Derivative of the Unknown Zintl Ion [Ge6]2−

Octahedral clusters from p-block elements are rare ; however, the only known molecular aggregate of this kind, [{(CO)₅Cr}₆Sn₆]²⁻, has now been supplemented by the isoelectronic cluster [{(CO)₅Cr}₆Ge₆]²⁻ ( 1 ).     

Step‐by‐Step Synthesis of the Endohedral Stannaspherene [Ir@Sn12]3− via the Capped Cluster Anion [Sn9Ir(cod)]3−

The endohedral stannaspherene cluster anion [Ir@Sn₁₂]^3? was synthesized in two steps. The reaction of K₄Sn₉ with [IrCl(cod)]₂ (cod: 1,5‐cyclooctadienyl) in ethylenediamine (en) solution first yielded the [K(2,2,2‐crypt)]⁺ salt (2,2,2‐crypt: 4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane) of the capped cluster anion [Sn₉Ir(cod)]^3?. Subsequently, crystals of this compound were dissolved in en, followed by the addition of triphenylphosphine or 1,2‐bis(diphenylphosphino)ethane and treatment at elevated temperatures. [Ir@Sn₁₂]^3? was obtained and characterized as the [K(2,2,2‐crypt)]⁺ salt. The isolation of [Sn₉Ir(cod)]^3? as an intermediate product establishes that the formation of the stannaspherene [Ir@Sn₁₂]^3? occurs through the oxidation of [Sn₉Ir(cod)]^3?. Among the structurally characterized tetrel cluster anions, [Ir@Sn₁₂]^3? is a unique example of a stannaspherene, and one of the rare spherical clusters encapsulating a metal atom that is not a member of Group 10. Single‐crystal structure determination shows that the novel Zintl ion cluster has nearly perfect icosahedral I_h point symmetry.