Ralf Köppe

[Al7{N(SiMe3)2}6]−: A First Step towards Aluminum Metal Formation by Disproportionation

A “naked” aluminum atom links two aluminum tetrahedra in the [Al7{N(SiMe3)2}6]− ion (see picture), which results from the reaction of a metastable AlCl solution with LiN(SiMe3)2 and crystallizes with [Li(OEt2)3]+ as cation. This unique structure among molecular metal atom clusters represents a small but characteristic section of cubic close-packed aluminum.

[{(η5-C5Me5)2Sm}4P8]: A Molecular Polyphosphide of the Rare-Earth Elements

[{(eta(5)-C(5)Me(5))(2)Sm}(4)P(8)], a molecular polyphosphide of the rare-earth elements having a realgar core structure, was synthesized by a one-electron redox reaction of divalent samarocen and white phosphorus.

Mixed‐Metal Lanthanide–Iron Triple‐Decker Complexes with a cyclo‐P5 Building Block

Tripleand multidecker sandwich complexes have been discussed in the last decades for their unique electrical and magnetic properties. The organic spacer between the metals may facilitate intermetallic electronic communication, which has a high potential for molecular electronics. A number of one-dimensional organometallic sandwich molecular wires (SMWs) have been extensively studied. Thus, the multilayer vanadium–arene (Ar) organometallic complexes [Vn(Ar)m], which can be produced in a molecular beam by laser vaporization, are a class of one-dimensional molecular magnets. Ferrocene-based molecular wires have been synthesized in the gas phase and characterized by mass spectroscopy. It was calculated that these compounds have half-metallic properties with 100 % negative spin polarization near the Fermi level in the ground state. In contrast to this investigation in the gas phase, studies on related organometallic tripleand multidecker sandwich complexes containing f-block elements (lanthanides or actinides) in condensed phase remain rare; studies were mostly on the cyclooctatetraene ligand and its derivatives. The only rare-earth-element triple-decker complex with heterocycles is the low-valent scandium 1,3,5-triphosphabenzene complex [{(hP3C2tBu2)Sc}2(m-h 6 :h-P3C3tBu3)], which was obtained by cocondensation of scandium vaporized in an electron beam with an excess of the phosphaalkyne tBuC P. Apart from organometallic compounds, tripleand multidecker sandwich complexes of the 4f elements consisting of “salen” type Schiff base ligands, phthalocyanines, and porphyrins have been extensively studied because these compounds exhibit tunable spectroscopic, electronic, and redox properties, and different extents of intramolecular p–p interactions. Despite these promising physical properties further investigations on 4f elements based tripleand multidecker sandwich complexes are obviously hampered by the limited variety of ligands that have been attached to the metal centers to date. Based on these considerations, we present herein mixed d/f-block-metal triple-decker complexes with a purely inorganic all-phosphorus middle deck. In contrast to d-block chemistry, where purely inorganic ring systems of Group 15 elements such as P5 and P6, [9] As5, [9c] and Sb5 [10] are well-established, there is no analogy with the fblock elements to date. On the other hand, it was shown only recently that rare-earth elements can stabilize highly reactive main-group species such as N2 3 . Although some heavier Group 15–lanthanide compounds, such as phosphides (Ln PR2), [12] arsenides (Ln AsR2), 13] stibides (Ln Sb3), and bismutides (Ln Bi Bi Ln) are known, the first molecular polyphosphide of the rare-earth elements, [(Cp*2Sm)4P8] (Cp* = h-C5Me5), was recently synthesized. [16] The structure of the complex is very rare and can be described as a realgartype P8 4 ligand trapped in a cage of four samarocenes. As no triple-decker sandwich complex of the rare-earth elements with a polyphosphide middle-deck bridging the metal centers is known, we focused our interest on the cyclo-P5 ligand. The structure and properties of this ligand are very similar to the well-known cyclopentadienyl anion (Scheme 1) and could therefore have many possible coordination modes.

Al22Br20⋅12 THF: das erste polyedrische Aluminiumsubhalogenid – ein Schritt auf dem Weg zu einer neuen Aluminiummodifikation?

Das erste polyedrische Aluminiumsubhalogenid Al22Br20⋅12 L entsteht bei der Disproportionierung von AlI-Bromid-Losungen. Der Cluster ist aus einem Al12-Ikosaeder mit zehn exohedral gebundenen (formal zweiwertigen) Al-Atomen aufgebaut (siehe Struktur). Ein derartiges homoatomares Gerust ist bei molekularen Verbindungen unbekannt. Selbst beim Element Bor findet man dieses Gerust lediglich als Ausschnitt aus der β-rhomboedrischen Elementmodifikation.

GaGa‐ und AlFe‐Mehrfachbindungen? Ein Interpretationsversuch auf der Grundlage von Kraftkonstanten

Mit Hilfe von Kraftkonstanten, die aus Frequenzrechnungen nach DFT-Methoden ermittelt wurden, wird gezeigt, dass die Bindungsverstarkungen ausgehend von der GaGa-Einfachbindung in Ga2H62–, zu GaGa-Bindungen in Ga2H42– und Ga2H22– so gering sind, dass nicht von Mehrfachbindungen gesprochen werden sollte. Demgegenuber zeigen vergleichbare Rechnungen fur Verbindungen mit FeAl-Bindungen (z. B. CpAlFe(CO)4), dass diese als Doppelbindungen interpretiert werden konnen. GaGa and AlFe Multiple Bonds? An Attempt of Interpretation on the Basis of Force Constants Comparison of force constant values given by DFT frequency calculations shows that GaGa-bonds in Ga2H42– and Ga2H22– are only slightly strengthened with respect to the GaGa-single bond in Ga2H62–. On the other hand FeAl bonds in compounds like CpAlFe(CO)4 are interpreted as double bonds.

Al22Br20⋅12 THF: The First Polyhedral Aluminum Subhalide—A Step on the Path to a New Modification of Aluminum?

The first polyhedral aluminum subhalide Al22 Br20 ⋅20 L forms in the disproportionation of aluminum(I) bromide solutions. The cluster is built up from an Al12 icosahedron with ten exohedrally bound (formally divalent) Al atoms (see structure). Such a homoatomic framework is unknown for molecular compounds. Even for the element boron this framework is only found as a section from the β-rhombohedral element modification.

Synthese von Germanium(I)-bromid. Ein erster Schritt zu neuen Clusterverbindungen des Germaniums?

Thermodynamic data for gaseous GeBr, derived from quantum chemical (DFT)-calculations show that this monohalide should be formed at 1550 °C as a product of the reaction of el- emental germanium with HBr at 110 2 mbar. Herein the design of an apparatus is described in which GeBr can be synthesized under these conditions and cocondensed with toluene at 196 °C. Using this technique 3 g of a dark red X-ray amorphous solid could

Aminotroponiminatozinc(I) Complexes: Syntheses and Spectroscopic Analyses

Low-valent metal-metal bonded compounds have generated growing interest over the last few years. Following the landmark discovery of Carmona s decamethyldizincocene ([(h-Cp*)2Zn2]; Cp*=C5Me5), [2] the first complex featuring a covalent Zn Zn bond, the synthesis and reactivity of lowvalent metal-metal bonded organozinc compounds has attracted a great deal of attention. Since this initial report, several low-valent dizinc compounds of the type R2Zn2 (R= EtMe4Cp, [3] {(2,6-iPr2C6H3)N(Me)C}2CH (Dippnacnac), [4] 2,6-(2,6-iPr2C6H3)2C6H3, [5] {(2,6-iPr2C6H3)N(Me)C}2, [6] {(2,6iPr2C6H3)NCH}2, [7] Me2Si{N(2,6-iPr2C6H3)}2, [8] 1,2-bis{(2,6diisopropylphenyl)imino}acenaphthene) have been synthesized and structurally characterized. In contrast, only very limited information is available on the chemical reactivity of such compounds. The reactions of [(h-Cp*)2Zn2] with H2O, tBuOH, and NCXyl resulted in the formation of elemental zinc and the corresponding Zn complexes through disproportionation pathways. The reaction with iodine occurred with oxidation and subsequent formation of [(h-Cp*)2Zn] and ZnI2, [3] whereas no reaction was observed with H2, CO, and CO2. Very recently, one of us reported on the reaction of [(h-Cp*)2Zn2] with the strong Lewis base 4-(dimethylamino)pyridine (dmap), which yielded [(h-Cp*)Zn–ZnACHTUNGTRENNUNG(dmap)2ACHTUNGTRENNUNG(h1-Cp*)], the first Lewis acid–base adduct of dizincocene. [(h-Cp*)Zn–Zn ACHTUNGTRENNUNG(dmap)2ACHTUNGTRENNUNG(h1-Cp*)] was found to react with [H ACHTUNGTRENNUNG(OEt2)2][Al{OC ACHTUNGTRENNUNG(CF3)3}4] to give the base-stabilized [Zn2] 2+ ion [Zn2ACHTUNGTRENNUNG(dmap)6][Al{OC ACHTUNGTRENNUNG(CF3)3}4]2.[11] Moreover, one of us successfully exchanged the Cp* ligand in [(h-Cp*)2Zn2] by reaction with [{2,4,6-Me3C6H2)N(Me)C}2CH] (MesnacnacH), to yield [(Mesnacnac)2Zn2]. [12] Carmona et al. reported on the synthesis of [Zn2(h -C5Me5)(OR)(L)x] (R=2,6-(2,4,6-Me3C6H2)2C6H3 and C5Me5; L=4-pyrrolidinopyridine). Moreover, reactions of [(h-Cp*)2Zn2] with bis(iminodi(phenyl)phosphorano)methanes yielded both homoand heteroleptic zinc(I) complexes. Evidently, the organic ligands have a great impact on the nature of the Zn Zn bond, such as bond length, bond strength, and orbital composition. Based on these observations we became interested in studying the nature of the Zn Zn bond in more detail including the spectroscopic properties. Herein, we report on the synthesis and characterization of two new zinc–zinc bonded compounds starting from [(h-Cp*)2Zn2]. The details of the vibrational modes supported by DFT calculations of the new compounds were investigated. We have been working for some time on aminotroponiminatozinc compounds. These complexes have been studied in detail for catalytic hydroamination catalysis. In this context we were interested in preparing low-valent aminotroponiminato zinc–zinc bonded compounds. Reaction of the aminotroponimines N-isopropyl-2-(isopropylamino)troponimine [{(iPr)2ATI}H] [17] and 4-bromo N-isopropyl-2-(isopropylamino)troponimine [{4-Br ACHTUNGTRENNUNG(iPr)2ATI}H][18] with [(h-Cp*)2Zn2] in toluene at room temperature resulted in the formation of [{(iPr)2ATI}2Zn2] (1) and [{4-Br ACHTUNGTRENNUNG(iPr)2ATI}2Zn2] (2). The Zn Zn bond is preserved under these protolytic conditions in the products (Scheme 1). The H and C{H} NMR spectroscopic data for compounds 1 and 2 are consistent with the solid-state structures (see Figure 1). No bridging hydride resonances were ob[a] Dr. H. P. Nayek, Dipl.-Chem. A. L hl, Dr. R. Kçppe, Prof. Dr. P. W. Roesky Institut f r Anorganische Chemie Karlsruhe Institute of Technology (KIT) Engesserstrasse 15, 76131 Karlsruhe (Germany) Fax: : (+49) 721-6084-854 E-mail : roesky@kit.edu [b] Prof. Dr. S. Schulz University of Duisburg-Essen Universit tsstrasse 5–7, S07 S03 C30, 45117 Essen (Germany) Fax: (+49) 2011833830 Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem201002443.

Catching gaseous SO2 in cone-type lanthanide complexes: an unexpected coordination mode for SO2 in f-element chemistry.

Easy come, easy go: the first molecular SO(2) complexes of the lanthanides (Ln=Sm, Eu) have been prepared. The compounds can reversibly coordinate gaseous SO(2). Concomitant with the addition and removal of SO(2), the color of the complexes changes reversibly. The structures of the SO(2) compounds could be confirmed in solution and in the solid state.

Ga19(C(SiMe3)3)6− as a precursor for pure and silicon-doped gallium clusters: a mass spectrometric study of a Ga13− and a Ga12Si− anion

Abstract The metalloid cluster [Ga19(C(SiMe3)3)6][Li2Br(THF)6] was studied by Fourier-transform ion cyclotron resonance-mass spectrometry (FT/ICR-MS). The spectrum obtained by laser desorption ionization (LDI) is dominated by pure gallium cluster anions Gan− with n ranging up to 50 and mixed gallium–silicon cluster anions GanSi−, GanSi2−, and GanSi3− with n ranging up to 43. A maximum of the cluster abundance is observed for Ga13− and Ga12Si−. These experimental results exhibit for the first time the formation of large pure and silicon-doped gallium clusters starting from a molecular compound. They are discussed in terms of the precursor’s structure and the simplified predictions of the jellium model. DFT calculations were employed to further evaluate the electronic properties of these anionic clusters, the results of which show that Ga13− favors a regular bicapped pentagonal prism (D5h) as well as Ga12Si−, Si being located in the center of the cluster.