Probing Charge-Transfer Processes in a Covalently Linked [Ge9]-Cluster Imine Dyad

C₆₀ donor dyads in which the carbon cage is covalently linked to an electron-donating unit have been discussed as one possibility for an electron-transfer system, and it has been shown that spherical [Ge₉] cluster anions show a close relation to fullerenes with respect to their electronic structure. However, the optical properties of these clusters and of functionalized cluster derivatives are almost unknown. We now report on the synthesis of the intensely red [Ge₉] cluster linked to an extended π-electron system. [Ge₉{Si(TMS)₃}₂{CH₃C=N}-DAB(II)^Dipp]⁻ ( 1⁻ ) is formed upon the reaction of [Ge₉{Si(TMS)₃}₂]²⁻ with bromo-diazaborole DAB(II)^Dipp-Br in CH₃CN (TMS=trimethylsilyl; DAB(II)=1,3,2-diazaborole with an unsaturated backbone; Dipp=2,6-di-iso-propylphenyl). Reversible protonation of the imine entity in 1⁻ yields the deep green, zwitterionic cluster [Ge₉{Si(TMS)₃}₂{CH₃C=N(H)}-DAB(II)^Dipp] ( 1-H ) and vice versa. Optical spectroscopy combined with time-dependent density functional theory suggests a charge-transfer excitation between the cluster and the antibonding π* orbital of the imine moiety as the cause of the intense coloration. An absorption maximum of 1-H in the red region of the electromagnetic spectrum and the corresponding lowest-energy excited state at λ=669 nm make the compound an interesting starting point for further investigations targeting the design of photo-active cluster compounds.     

On the Nature of Bridging Metal Atoms in Intermetalloid Clusters: Synthesis and Structure of the Metal‐Atom‐Bridged Zintl Clusters [Sn(Ge9)2]4− and [Zn(Ge9)2)]6−

The addition of Sn and Zn ions to [Ge₉] clusters by reaction of [Ge₉]^4? with SnPh₂Cl₂, ZnCp*₂ (Cp*=pentamethylcyclopentadienyl), or Zn₂[HC(Ph₂P=NPh)₂]₂ is reported. The resulting Sn‐ and Zn‐bridged clusters [(Ge₉)M(Ge₉)]^q? (M=Sn, q=4; M=Zn, q=6) display various coordination modes. The M atoms that coordinate to the open square of a C_4v‐symmetric [Ge₉] cluster form strong covalent multicenter M?Ge bonds, in contrast to the M atoms coordinating to triangular cluster faces. Molecular orbital analyses show that the M atoms of the Ge₉M fragments coordinate to a second [Ge₉] cluster with similar orbitals but in different ways. The [Ge₉Sn]^2?unit donates two electrons to the triangular face of a second [Ge₉]^2? cluster with D_3h symmetry, whereas [Ge₉Zn]^2?acts as an electron acceptor when interacting with the triangular face of a D_3h‐symmetric [Ge₉]^4? unit.     

The Weakly Coordinating Tris(trichlorosilyl)silyl Anion

Closely following the procedure for the preparation of the base‐stabilized dichlorosilylene complex NHC^Dipp⋅SiCl₂ reported by Roesky, Stalke, and co‐workers (Angew. Chem. Int. Ed . 2009 , 48 , 5683–5686), a few crystals of the salt [NHC^Dipp−H⋅⋅⋅Cl⋅⋅⋅H−NHC^Dipp]Si(SiCl₃)₃ were isolated, aside from the reported byproduct [NHC^Dipp−H⁺⋅⋅⋅Cl⁻], and characterized by X‐ray crystallography (NHC^Dipp=N,N‐di(2,6‐diisopropylphenyl)imidazo‐2‐ylidene). They contain the weakly coordinating anion Si(SiCl₃)₃⁻, which was also obtained in high yields upon deprotonation of the conjugate Brønsted acid HSi(SiCl₃)₃ with NHC^Dipp or PMP (PMP=1,2,2,6,6‐pentamethylpiperidine). The acidity of HSi(SiCl₃)₃ was estimated by DFT calculations to be substantially higher than those of other H‐silanes. Further DFT studies on the electronic structure of Si(SiCl₃)₃⁻, including the electrostatic potential and the electron localizability, confirmed its low basicity and nucleophilicity compared with other silyl anions.     

FLP-type nitrile activation and cyclic ether ring-opening by halo-borane nonagermanide-cluster Lewis acid–base pairs

Even though homoatomic nine-atom germanium clusters are known for two decades, their chemical properties are still rarely investigated. We now discovered that Zintl ion main group-element clusters possess a reactive lone pair of electrons, and we show a new pathway to bind ligands with functional groups to the [Ge₉] cluster core through Ge–C bond formation. We report on the reactivity of [Ge₉{Si(TMS)₃}₂]²⁻ (TMS = trimethylsilyl) towards a series of Lewis acidic bromo-boranes. The reaction of [Ge₉{Si(TMS)₃}₂]²⁻ and DAB^o-tol–Br (DAB = 1,3,2-diazaborolidine; o-tol = 2-methylphenyl) resulted, depending on the reaction protocol, either in the formation of [Ge₉{Si(TMS)₃}₂DAB^o-tol]⁻ (1a) with direct Ge–B interactions, or in [Ge₉{Si(TMS)₃}₂(CH₂)₄O–DAB^o-tol]⁻ (2a) featuring a ring-opened thf moiety. Ring opening reactions occur for all bulkier DAB^R–Br [R: o-xyl (2,6-dimethylphenyl), Mes (2,4,6-trimethylphenyl), Dipp (2,6-diisopropylphenyl)], DAB(ii)^Dipp–Br and acyclic (ⁱPr₂N)₂BBr without Ge–B bond formation as shown for the structural characterization of the ring-opened products of thf (3, 4) and trimethylene oxide (5). In contrast to thf, the activation of CH₃CN requires the simultaneous presence of Lewis-acid and Lewis-basic reactants allowing the formation of [Ge₉{Si(TMS)₃}₂CH₃C N–DAB^Mes]⁻ (6a). Within the presented compounds, 3 and 4 show an unusual substitution pattern of the three ligands at the [Ge₉] core in the solid state. The [Ge₉] cluster/borane systems correspond to intermolecular frustrated Lewis pairs (FLPs), in which the [Ge₉] cluster with several lone pairs represents the Lewis base, and the borane is the Lewis acid.

The reactivity of the lone pairs in polyhedral Zintl anions is shown by the reaction of the bis-silylated cluster [Ge₉{Si(TMS)₃}₂]²⁻ accomplishing cyclic-ether ring-opening or nitrile activation according to a FLP-like mechanism with bromo-boranes.     

Functionalization of [Ge9] with Small Silanes:[Ge9(SiR3)3]– (R = iBu,iPr, Et) and the Structures of (CuNHCDipp)[Ge9{Si(iBu)3}3], (K‐18c6)Au[Ge9{Si(iBu)3}3]2, and (K‐18c6)2[Ge9{Si(iBu)3}2]

Novel silylation reactions at [Ge₉] Zintl clusters starting from the chlorosilanes SiR₃Cl (R = iBu, iPr, Et) and the Zintl phase K₄Ge₉ are reported. The formation of the tris‐silylated anions [Ge₉(SiR₃)₃]^– [R = iBu ( 1a ), iPr ( 1b ), Et ( 1c )] by heterogeneous reactions in acetonitrile was monitored by ESI‐MS measurements. For R = iBu ¹H, ¹³C and ²⁹Si NMR experiments confirmed the exclusive formation of 1a . Subsequent reactions of 1a with CuNHC^DippCl and Au(PPh₃)Cl result in formation of the neutral metal complex (CuNHC^Dipp)[Ge₉{Si(iBu)₃}₃]·0.5 tol ( 2 ·0.5 tol) and the metal bridged dimeric unit {Au[Ge₉{Si(iBu)₃}₃]₂}^– ( 3a ), isolated as a (K‐18c6)⁺ salt in (K‐18c6)Au[Ge₉{Si(iBu)₃}₃]₂·tol ( 3 ·tol), respectively. Finally, from a toluene/hexane solution of 1a in presence of 18‐crown‐6, crystals of the compound (K‐18c6)₂[Ge₉{Si(iBu)₃}₂]·tol ( 4 ·tol), containing the bis‐silylated cluster anion [Ge₉(Si(iBu)₃)₂]^2– ( 4a ), were obtained. The compounds 2 ·0.5 tol, 3 ·tol and 4 ·tol were characterized by single‐crystal structure determination.     

Synthesis and Characterization of an Eclipsed Digermylene as a Building Block to Construct a Cyclic Octagermylene

The preparation of an unprecedented Ge^I‐Ge^I bonded digermylene [K₂{Ge₂(μ‐κ²:η²:η⁴‐2,6‐(2,6‐ⁱPr₂C₆H₃‐N)₂‐4‐CH₃C₅H₂N)₂}] in an eclipsed conformation stabilized by two bridging diamidopyridyl ligands is presented. Although it exhibits an eclipsed conformation, the Ge−Ge bond length is 2.5168(6) Å, which is shorter than those in the trans ‐bent and gauche digermylenes. In combination with two pendant amido groups, the Ge^I₂ motif is employed as a building block to assemble the first example of octagermylene [Ge₄(μ‐κ²:κ¹‐2,6‐(2,6‐ⁱPr₂C₆H₃‐N)₂‐4‐CH₃C₅H₂N)₂]₂ showing a cyclic configuration and containing three distinct types of Ge^I−Ge^I bonds.     

[Nb@Ge13/14]3−: New Family Members of Ge-Based Intermetalloid Clusters

During the past two decades, single-atom-centered medium-sized germanium clusters [M@Ge_n] (M=transition metals, n>12) have been extensively explored, both from theoretical perspectives and experimental gas-phase syntheses. However, the actual structural arrangements of the Ge₁₃ and Ge₁₄ endohedral cages are still ambiguous and have long remained an unresolved problem for experimental implementation. In this work, we successfully synthesize 13-/14-vertex Ge clusters [Nb@Ge₁₃]³⁻ ( 1 ) and [Nb@Ge₁₄]³⁻ ( 2 ), which are structurally characterized and exhibit unprecedented topologies, neither classical deltahedra nor 3-connected polyhedral structures. Theoretical analysis indicates that the major stabilization of the Ge backbones arises due to the substantial interaction of Ge 4p-AOs with the endohedral Nb 4d-AOs through three/four-center two-electron bonds with an enhanced electron density accumulated over the shortest Nb−Ge13 contact in 1 . Low occupancies of the direct two-center two-electron (2c–2e) Nb−Ge and Ge−Ge σ bonds point to a considerable degree of electron delocalization over the Ge cages revealing their electron deficiency.     

Zintl Clusters as Wet‐Chemical Precursors for Germanium Nanomorphologies with Tunable Composition

[Ge₉]^4? Zintl clusters are used as soluble germanium source for a bottom–up fabrication of Ge nanomorphologies such as inverse opal structures with tunable composition. The method is based on the assembly and oxidation of [Ge₉]^4? clusters in a template mold using SiCl₄, GeCl₄, and PCl₃ leading to Si and P‐containing Ge phases as shown by X‐ray diffraction, Raman spectroscopy, and energy‐dispersive X‐ray analysis. [Ge₉]^4? clusters are retained using ethylenediamine (en) as a transfer medium to a mold after removal of the solvent if water is thoroughly excluded, but are oxidized to amorphous Ge in presence of water traces. ¹H NMR spectroscopy reveals the oxidative deprotonation of en by [Ge₉]^4?. Subsequent annealing leads to crystalline Ge. As an example for wet‐chemical synthesis of complex Ge nanomorphologies, we describe the fabrication of undoped and P‐doped inverse opal‐structured Ge films with a rather low oxygen contents. The morphology of the films with regular volume porosity is characterized by SEM, TEM, and grazing incidence small‐angle X‐ray scattering.     

On the Reactivity of Silylated Ge9 Clusters: Synthesis and Characterization of [ZnCp*(Ge9{Si(SiMe3)3}3)], [CuPiPr3(Ge9{Si(SiMe3)3}3)], and [(CuPiPr3)4{Ge9(SiPh3)2}2]

We report on the synthesis of new derivatives of silylated clusters of the type [Ge₉(SiR₃)₃]^? (R = SiMe₃, Me = CH₃; R = Ph, Ph = C₆H₅) as well as on their reactivity towards copper and zinc compounds. The silylated cluster compounds were synthesized by heterogeneous reactions starting from the Zintl phase K₄Ge₉. Reaction of K[Ge₉{Si(SiMe₃)₃}₃] with ZnCl₂ leads to the already known dimeric compound [Zn(Ge₉{Si(SiMe₃)₃}₃)₂] ( 1 ), whereas upon the reaction with [ZnCp*₂] the coordination of [ZnCp*]⁺ to the cluster takes place (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) under the formation of [ZnCp*(Ge₉{Si(SiMe₃)₃}₃)] ( 2 ). A similar reaction leads to [CuPiPr₃(Ge₉{Si(SiMe₃)₃}₃)] ( 3 ) from [CuPiPr₃Cl] (iPr=isopropyl). Further we investigated the novel silylated cluster units [Ge₉(SiPh₃)₃]^? ( 4 ) and [Ge₉(SiPh₃)₂]^? ( 5 ), which could be identified by mass spectroscopy. Bis‐ and tris‐silylated species can be synthesized by the respective stoichiometric reactions, and the products were characterized by ESI‐MS and NMR experiments. These clusters show rather different reactivity. The reaction of the tris‐silylated anion 4 with [CuPiPr₃Cl] leads to [(CuPiPr₃)₃Ge₉(SiPh₃)₂]⁺ as shown from NMR experiments and to [(CuPiPr₃)₄{Ge₉(SiPh₃)₂}₂] ( 6 ), which was characterized by single‐crystal X‐ray diffraction. Compound 6 shows a new type of coordination of the Cu atoms to the silylated Zintl clusters.     

[Ge9{Si(SiMe3)3}2{Ge(SiMe3)3}]–: The Mixed Substituted Metalloid Germanium Cluster and the Intermetalloid Cluster [ZnGe18{Si(SiMe3)3}4{Ge(SiMe3)3}2]

The novel metalloid germanium cluster [Ge₉(Hyp)₂Hyp^Ge]^– ( 1 ) was synthesized, exhibiting two different bulky groups [Hyp = Si(SiMe₃)₃; Hyp^Ge = Ge(SiMe₃)₃]. Further reaction of 1 with ZnCl₂ gives the derivative [ZnGe₁₈(Hyp)₄(Hyp^Ge)₂] ( 2 ) in good yield, showing that the substitution of Si(SiMe₃)₃ by Ge(SiMe₃)₃ within a metalloid Ge₉R₃^– compound leads to a comparable reactivity. 1 and 2 are characterized by NMR spectroscopy, mass spectrometry ( 1 ) and single crystal structure analyses ( 2 ). 1 and 2 are the first metalloid germanium clusters bearing germyl groups.     

The Sodium Antimony Telluridogermanate(III) Na9Sb[Ge2Te6]2

Systematic studies in the quaternary system Na/Ge/Sb/Te yielded the new compound Na₉Sb[Ge₂Te₆]₂. Its crystal structure is isotypic to Na₉Sb[Ge₂Se₆]₂ (space group C2/c with a = 9.541(2), b = 26.253(7), c = 7.5820(18) Å and β = 122.233(15)°, Z = 2). The structure is characterized by Ge–Ge dumbbells that are octahedrally coordinated by Te, forming ethane‐like [Ge₂Te₆]^6– anions. Cation sites are occupied by Na⁺ as well as shared by Na⁺ and Sb³⁺. Na₉Sb[Ge₂Te₆]₂ is formally obtained from the reaction of one equivalent Na₈[Ge₄Te₁₀] and one equivalent NaSbTe₂. In contrast to members of the metastable solid solution series (NaSbTe₂)_1–x(GeTe)_x, Na₉Sb[Ge₂Te₆]₂ is a thermodynamically stable compound. It is a semiconductor with a bandgap of 1.51 eV.     

Na12Ge17: A Compound with the Zintl Anions [Ge4]4— and [Ge9]4— — Synthesis,Crystal Structure,and Raman Spectrum

Na₁₂Ge₁₇ is prepared from the elements at 1025 K in sealed niobium ampoules. The crystal structure reinvestigation reveals a doubling of the unit cell (space group:P2₁/c; a = 22.117(3)Å, b = 12.803(3)Å, c = 41.557(6)Å, β = 91.31(2)°, Z = 16; Pearson code: mP464), furthermore, weak superstructure reflections indicate an even larger C‐centred monoclinic cell. The characteristic structural units are the isolated cluster anions [Ge₉]^4— and [Ge₄]^4— in ratio 1:2, respectively. The crystal structure represents a hierarchical cluster replacement structure of the hexagonal Laves phase MgZn₂ in which the Mg and Zn atoms are replaced by the Ge₉ and Ge₄ units, respectively. The Raman spectrum of Na₁₂Ge₁₇ exhibits the characteristic breathing modes of the constituent cluster anions at ν = 274 cm^—1 ([Ge₉]^4—) and ν = 222 cm^—1 ([Ge₄]^4—) which may be used for identification of these clusters in solid phases and in solutions. Raman spectra further prove that Na₁₂Ge₁₇ is partial soluble both in ethylenediamine and liquid ammonia. The solution and the solid extract contain solely [Ge₉]^4—. The remaining insoluble residue is Na₄Ge₄. By heating the solvate Na₄Ge₉(NH₃)_n releases NH₃ and decomposes irreversibly at 742 K, yielding Na₁₂Ge₁₇ and Ge.     

The Nature of the UC Double Bond: Pushing the Stability of High‐Oxidation‐State Uranium Carbenes to the Limit

Treatment of [K(BIPM^MesH)] (BIPM^Mes={C(PPh₂NMes)₂}^2?; Mes=C₆H₂‐2,4,6‐Me₃) with [UCl₄(thf)₃] (1 equiv) afforded [U(BIPM^MesH)(Cl)₃(thf)] ( 1 ), which generated [U(BIPM^Mes)(Cl)₂(thf)₂] ( 2 ), following treatment with benzyl potassium. Attempts to oxidise 2 resulted in intractable mixtures, ligand scrambling to give [U(BIPM^Mes)₂] or the formation of [U(BIPM^MesH)(O)₂(Cl)(thf)] ( 3 ). The complex [U(BIPM^Dipp)(μ‐Cl)₄(Li)₂(OEt₂)(tmeda)] ( 4 ) (BIPM^Dipp={C(PPh₂NDipp)₂}^2?; Dipp=C₆H₃‐2,6‐iPr₂; tmeda=N,N,N′,N′‐tetramethylethylenediamine) was prepared from [Li₂(BIPM^Dipp)(tmeda)] and [UCl₄(thf)₃] and, following reflux in toluene, could be isolated as [U(BIPM^Dipp)(Cl)₂(thf)₂] ( 5 ). Treatment of 4 with iodine (0.5 equiv) afforded [U(BIPM^Dipp)(Cl)₂(μ‐Cl)₂(Li)(thf)₂] ( 6 ). Complex 6 resists oxidation, and treating 4 or 5 with N‐oxides gives [{U(BIPM^DippH)(O)₂‐ (μ‐Cl)₂Li(tmeda)] ( 7 ) and [{U(BIPM^DippH)(O)₂(μ‐Cl)}₂] ( 8 ). Treatment of 4 with tBuOLi (3 equiv) and I₂ (1 equiv) gives [U(BIPM^Dipp)(OtBu)₃(I)] ( 9 ), which represents an exceptionally rare example of a crystallographically authenticated uranium(VI)–carbon σ bond. Although 9 appears sterically saturated, it decomposes over time to give [U(BIPM^Dipp)(OtBu)₃]. Complex 4 reacts with PhCOtBu and Ph₂CO to form [U(BIPM^Dipp)(μ‐Cl)₄(Li)₂(tmeda)(OCPhtBu)] ( 10 ) and [U(BIPM^Dipp)(Cl)(μ‐Cl)₂(Li)(tmeda)(OCPh₂)] ( 11 ). In contrast, complex 5 does not react with PhCOtBu and Ph₂CO, which we attribute to steric blocking. However, complexes 5 and 6 react with PhCHO to afford (DippNPPh₂)₂C?C(H)Ph ( 12 ). Complex 9 does not react with PhCOtBu, Ph₂CO or PhCHO; this is attributed to steric blocking. Theoretical calculations have enabled a qualitative bracketing of the extent of covalency in early‐metal carbenes as a function of metal, oxidation state and the number of phosphanyl substituents, revealing modest covalent contributions to U?C double bonds.     

Assembly of One to Four As4 Analogues, (Ge2As2)2− or (Ge3As)3−, in the Coordination Sphere of [PhM]+, [MesM]+, or M2+ (M=Zn,Cd, Hg)

Pseudo-tetrahedral units of p-block atoms proved to be excellent building blocks for novel molecular architectures and for introducing new elemental combinations which are not otherwise accessible. In this work, we present a series of clusters obtained by reactions of binary Ge/As anions with [MPh₂] (M=Zn, Cd, Hg; Ph=phenyl). The study is grounded on the fact that the binary reactant gained by extracting the solid ‘K₂GeAs’ with ethane-1,2-diamine (en) co-exists as (Ge₂As₂)²⁻ and (Ge₃As)³⁻ in solution. This allows for a larger variety of products by ‘selecting’ the most suitable species for the final ternary complex to crystallize. The reactions afforded the unprecedented first step of the corresponding interaction, thus attachment of (MPh)⁺ to a pseudo-tetrahedral unit in [PhZn(Ge₃As)]²⁻ ( 1 ) and [PhHg(Ge₃As)]²⁻ ( 2 ), and complex anions with two, three, or four units, [(Ge₃As)Zn(Ge₂As₂)]³⁻ ( 3 ), [Cd₃(Ge₃As)₃]³⁻ ( 4 ), and [Zn₃(Ge₃As)₄]⁶⁻ ( 5 ). Quantum chemistry confirmed the compositions and the positions of the Ge or As atoms, beside explaining structural peculiarities. The subtle impact of different [MR₂] reactants was additionally studied by corresponding reactions using [ZnMes₂] (Mes=mesityl), which showed success in selectively crystallizing [MesZn(Ge₃As)]²⁻ ( 6 ). Based on our findings, we derive a suggestion of the underlying reaction cascade.     

Crystal Growth and Structure Refinement of K4Ge9

Deep‐red moisture and air sensitive single crystals of K₄Ge₉ were obtained by reacting GeO₂ and elemental Ge with metallic W and K at high temperature in a niobium ampoule. The crystal structure of the compound was determined by single crystal X‐ray diffraction experiments. K₄Ge₉ crystallizes in a polar space group R3c (No. 161), Z = 4 with a = 21.208(1) and c = 25.096(2) Å. The compound contains discrete Ge₉^4? Wade's nido‐clusters which are packed according to a hierarchical atom‐to‐cluster replacement of the Cr₃Si prototype and are separated by K⁺ cations. Two independent [Ge₉]^4? clusters A (at Cr positions) and B (at Si positions) are found with a ratio A:B = 3:1. The B ‐type cluster satisfactorily represents orientational disorder around the three‐fold axis.     

Two‐, One‐, and Zero‐Dimensional Elemental Nanostructures Based on Ge9‐Clusters

We investigated the structural principles of novel germanium modifications derived by oxidative coupling of Zintl‐type [Ge₉]^4?clusters in various ways. The structures, stabilities, and electronic properties of the predicted {²_∞[Ge₉]_n} sheet, {¹_∞[Ge₉]_n} nanotubes, and fullerene‐like {Ge₉}_n cages were studied by using quantum chemical methods. The polyhedral {Ge₉}_n cages are energetically comparable with bulk‐like nanostructures of the same size, in good agreement with previous experimental findings. Three‐dimensional structures derived from the structures of lower dimensionality are expected to shed light on the structural characteristics of the existing mesoporous Ge materials that possess promising optoelectronic properties. Furthermore, 3D networks derived from the polyhedral {Ge₉}_n cages lead to structures that are closely related to the well‐known LTA zeolite framework, suggesting further possibilities for deriving novel mesoporous modifications of germanium. Raman and IR spectra and simulated X‐ray diffraction patterns of the predicted materials are given to facilitate comparisons with experimental results. The studied novel germanium modifications are semiconducting, and several structure types possess noticeably larger band gaps than bulk α‐Ge.     

Tetrarubidium Nonagermanide(4–) Ethylenediamine,Rb4[Ge9][en]

Tetrarubidiumnonagermanid(4–)-ethylendiamin, Rb₄[Ge₉][en] Orange-farbene Kristalle von Rb₄[Ge₉][en] erhält man nach der Austauschreaktion einer Lösung von ,NaGe_2.25‘ (precursor) in Ethylendiamin (en) mit festem RbI bei 360 K und nachfolgender langsamer Abkühlung. Die Verbindung ist äußerst empfindlich gegen Oxidation und Hydrolyse. Der thermische Abbau im dynamischen Vakuum beginnt mit der vollständigen Abgabe von en bei 350 K. Es folgt die Sublimation von Rubidium in vier weiteren Stufen (Rb₈Ge₂₅, Rb₈Ge₄₄, Rb_xGe₁₃₆ mit x È 16, Ge). Das Ramanspektrum zeigt die charakteristischen Banden des Anions [Ge₉]^4– bei 151, 163, 185 und 222 cm^–1. Rb₄[Ge₉][en] kristallisiert in einem neuen Strukturtyp (Raumgruppe P2₁/m; a = 15.353 Å, b = 16.434 Å, c = 15.539 Å, β = 113.75°; Z = 6; Pearsonsymbol mP198-40), der als hierarchische Variante der Strukturen von Al₄YbMo₂ und CrB₄ (hierarchische Basistypen, „initiators”︁) beschrieben werden kann, indem Atome partiell durch Aggregate ersetzt werden: B₄[□][Cr] ≙ Al₄[Yb][Mo]₂ ≙ Rb₄[Ge₉][en]_1–2. Drei kristallographisch unabhängige [Ge₉]^4–-Cluster sind in ein vierbindiges 46⁵-Netz aus Rb-Atomen eingebettet, ein Netzwerk kondensierter Tetraasterane. Die Cluster sind verzerrte überkappte tetragonale Antiprismen mit D₁(Ge–Ge) = 2.57 Å (16 Ç ) und D₂(Ge–Ge) = 2.84 Å (4 Ç ). Die Atome der Cluster mit D₁ und D₂ liegen auf der Oberfläche eines Rotationsellipsoids (a = b = 2.136 Å, c = 2.431 Å). Die en-Moleküle befinden sich in offenen Kanälen entlang [1¯ 0 1]. Die Koordinationen [Ge₉]Rb_12/4 und Rb [Ge₉]_4/12 en_2/8 zeigen, daß beim ersten Schritt der Solvatisierung Kationen und Clusteranionen nicht voneinander getrennt werden.     

Structures and mutual transformations of isomers of germylium ions (CH<Subscript>3</Subscript>)H<Subscript>2</Subscript>Ge<Superscript>+</Superscript> and (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>HGe<Superscript>+</Superscript> and their silicon analogs

The potential energy surfaces of the (CH₃)_nH_3?n M⁺ ions, where n = 1, 2; M = Si, Ge, were scanned using the B3LYP method with 6–31G* and aug-cc-pVDZ basis sets. The major attention was given to isomeric species having the form of complexes of the HM⁺ and CH₃M⁺ ions with hydrogen, methane, and ethane molecules. These species were characterized previously neither by experimental nor by theoretical methods. It was found that these species become more stable in going from Si to Ge; the complex [CH₃Ge⁺CH₄] is the second isomer in the energy after (CH₃)₂HGe⁺. However, the heights of the activation barriers to formation of these complexes from the most stable isomer, though decreasing in going from Si to Ge, remain relatively high and, what is particularly important, somewhat exceed the activation barrier to formation of the complex [H₃Ge⁺·C₂H₄].     

Extraction of Ternary Alloys: Synthesis and Crystal Structure of [K([2.2.2]crypt)]Cs7[Sn9]2(en)3

The compound [K([2.2.2]crypt)]Cs₇[Sn₉]₂(en)₃ ( 1 ) was synthesized from an alloy of formal composition KCs₂Sn₉ by dissolving in ethylenediamine (en) followed by the addition of [2.2.2]crypt and toluene. 1 crystallizes in the orthorhombic space group Pcca with a = 45.38(2), b = 9.092(4), c = 18.459(8) Å, and Z = 4. The structure consists of Cs₇[Sn₉]₂ layers which contain [Sn₉]^4– anions and Cs⁺ cations. The layers are separated by [K([2.2.2]crypt)]⁺ units. In the intermetallic slab (Cs₇[Sn₉]₂)^– compares the arrangement of pairs of symmetry‐related [Sn₉]^4– anions with the dimer ([Ge₉]–[Ge₉])^6– in [K([2.2.2]crypt)]₂Cs₄([Ge₉]–[Ge₉]), in which the clusters are linked by a cluster‐exo bond. The shortest distance between atoms of such two clusters in 1 is 4.762 Å, e. g. there are no exo Sn‐Sn bonds. The [Sn₉]^4– anion has almost perfect C_4v‐symmetry.     

Spirocyclic Boraamidinate Complexes of Lanthanide(III) Metals

The reaction of Li₂[Phbam^Dipp] (Phbam^Dipp = PhB(NDipp)₂; Dipp = 2,6‐iPr₂C₆H₃) with lanthanum(III) triiodides LnI₃(THF)_3.5 (Ln = La, Sm) in THF produces complexes of the type [Li(THF)₄]₂[(Phbam^Dipp)₂LnI], which were characterized in solution by multinuclear NMR spectroscopy and in the solid state by single‐crystal X‐ray structural determinations. The ion‐separated complexes are comprised of a spirocyclic anion in which two Phbam^Dipp ligands and an iodide ion are linked to the five‐coordinate metal atom; charge balance is provided by two tetrasolvated lithium ions [Li(THF)₄]⁺.