Synthesis and Reactivity of Fluorenyl-Based Germanium(II) Compounds

We present the synthesis of alkyl-substituted germylenes GeFlu2, Ge(FluTMS)2, and FluTMSGeCl (Flu = 9H-fluorenyl, FluTMS = 9-trimethylsilyl-9H-fluorenyl) using bulky fluorenyl ring systems and modifications of that. GeFlu2 can only be crystallized as its three-membered ring trimer, whereby the reaction is accompanied by the formation of several byproducts, such as [Li(THF)4][Ge(Ge3Flu7H)]. These results led to the modification of the fluorenyl framework by substitution the one H atom in the 9-position by a TMS group. With the synthesis of the corresponding Li salt LiFluTMS, Ge(FluTMS)2 could be isolated in good yields in a further reaction. The homoleptic Ge(FluTMS)2 is found in its crystalline form as a monomer and thus belongs to the series of monomeric alkyl-substituted germylenes. Also, the corresponding monoalkyl-substituted halogenido germylene was isolated as a four-membered ring tetramer [FluTMSGeCl]4 during an unselective reaction. However, FluTMSGeCl undergoes significant stabilization through the formation of the monomeric phosphane adduct FluTMSGeCl·PEt3, which greatly increases the selectivity of the reaction. During further reactions of Ge(FluTMS)2 with a GeBr solution (toluol/nPr3P), more impressions of the reactivity of Ge(I)X solutions with germylenes were achieved, showing that those germylenes take part in the disproportionation reaction of metastable Ge(I) solutions to give oxidized Ge(IV) compounds like (FluTMS)2GeBr2.

Oxidative coupling of silylated nonagermanide clusters

Polyhedral main group element clusters of tetrel elements are discussed as suitable building units to form atom-precise nano-structures. Herein we report the oxidative coupling of two [Ge₉{Si(TMS)₃}₂]^2- clusters (TMS = trimethylsilyl) resulting in the dimeric cluster [Ge₉{Si(TMS)₃}₂]₂^2-. The dimer is structurally characterized as the [NHC^iPrCu]⁺ adduct {NHC^iPrCu[Ge₉{Si(TMS)₃}₂]}₂ [NHC^iPr = 1,3-di(isopropyl)imidazolylidine]. The linkage of two molecular [Ge₉{Si(TMS)₃}₂]^2- anions under formation of an exo Ge-Ge bond occurs in the presence of Cy₂BCl (Cy = cyclohexyl) and is mediated by trace amounts of oxygen as indicated by the isolation of the by-product Cy₂B-O-BCy₂.

Structural Chemistry of Giant Metal Based Supramolecules

The review presents a bird-eye view on the state of research in the field of giant nonbiological discrete metal complexes and ions of nanometer size, which are structurally characterized by means of single-crystal X-ray diffraction, using the crystal structure as a common key feature. The discussion is focused on the main structural features of the metal clusters, the clusters containing compact metal oxide/hydroxide/chalcogenide core, ligand-based metal-organic cages, and supramolecules as well as on the aspects related to the packing of the molecules or ions in the crystal and the methodological aspects of the single-crystal neutron and X-ray diffraction of these compounds.

Deprotonation of Organogermanium and Organotin Trihydrides

Terphenyltin and terphenylgermanium trihydrides were deprotonated in reaction with strong bases, such as LiMe, LDA, or KBn. In the solid state, the Li salts of the germate anion 4 and 4a exhibit a Li-Ge contact. In the Li salt of the dihydridostannate anion 6a, the Li cation is not coordinated at the tin atom instead an interaction of the Li cation with the hydride substituents was found. Evidenced by ¹H-⁷Li-HOESY NMR spectroscopy the Li-salt of the deprotonated tin hydride 6a exhibits in toluene solution a contact between Li cation and hydride substituents, whereas in the ¹H-⁷Li-HOESY NMR spectrum of the homologous germate salt 4a, no crosspeak between hydride and Li signals was found. The organodihydridogermate and -stannate react as nucleophiles with low-valent Group 14 electrophiles. Thus, three compounds were synthesized: Ar-Ë'-EH₂-Ar (E', E = Sn, Ge; Pb, Ge; Pb, Sn; Ar = Ar', Ar*). Following an alternative synthesis Ar'SnH₂PbAr* was synthesized in reaction between [(Ar*PbH)₂] and [(Ar'SnH)₄] generated in situ. In reaction between low-valent organotin hydride [(Ar*SnH)₂] and organdihydridostannate [Ar*SnH₂]^- formation of distannate [Ar*₂Sn₂H₃]^- was found.

Enhancing the Variability of [Ge9 ] Cluster Chemistry through Phosphine Functionalization

The synthetic approach towards molecules that contain Ge atoms with oxidation state 0, and which are exclusively connected to other Ge atoms, is explored by using anionic clusters extracted from binary solids. Besides providing a novel variable method for the introduction of alkenyl moieties to [Ge₉ ] cluster compounds, this work expands the spectrum of mixed-functionalized [Ge₉ ] cluster anions, which are suitable for the straightforward synthesis of zwitterionic compounds upon coordination to metal cations. In detail, the synthesis of a series of mixed-functionalized [Ge₉ ] clusters is reported, including [Ge₉ {Si(TMS)₃ }₃ PRR^I ] (R=tBu, R^I =(CH₂ )₃ CH=CH₂ ; 2) and [Ge₉ {Si(TMS)₃ }₂ PRR^I ]^- (R and R^I : alkyl, alkenyl, aryl, aminoalkyl; 3 a to 11 a, TMS: (trimethyl)silyl). In 2 and 3 a, pentenyl functionalization of the [Ge₉ ] clusters was achieved by reaction of the novel chlorophosphine tBu{(CH₂ )₃ CH=CH₂ }PCl (1) with silylated [Ge₉ ] clusters. Furthermore, the reactivity of the cluster anions 3 a to 11 a towards NHC^Dipp MCl (NHC^Dipp =1,3-di(2,6-diisopropylphenyl)imidazolylidine; M=Cu, Ag) showed a dependency on the steric demand of the phosphine either zwitterions (3-MNHC^Dipp to 7-MNHC^Dipp ) featuring P-M interactions are formed, or Ge-M coordination (8-MNHC^Dipp to 11-MNHC^Dipp ) occurs. For M=Ag, the formation of zwitterionic complexes was unequivocally proven by NMR investigations showing ¹ J(³¹ P-¹⁰⁷ Ag/¹⁰⁹ Ag) spin-spin coupling.

A Re-examination of the Synthesis of Monolayer-Protected Co x(SCH2CH2Ph) m Nanoclusters: Unexpected Formation of a Thiolate-Protected Co(II) T3 Supertetrahedron

Herein, we report a re-examination of the synthesis and characterization of monolayer-protected Co _x(SCH₂CH₂Ph) _m nanoclusters. These clusters were reportedly formed by the reaction of CoCl₂ with NaBH₄ in the presence of HSCH₂CH₂Ph and were suggested to contain between 25 and 30 Co atoms. In our hands, however, we found no experimental evidence to support the existence of these large clusters in the reaction mixture. Instead, this reaction results in the relatively clean formation of the cobalt(II) coordination complex [Co₁₀(SCH₂CH₂Ph)₁₆Cl₄] (1). Complex 1 has been fully characterized using a wide variety of techniques, including single-crystal X-ray crystallography, NMR spectroscopy, mass spectrometry, and magnetometry. This complex represents the first example of a thiolate-protected Co(II) T3 supertetrahedral cluster.

Ge14 Br8 (PEt3 )4 : A Subhalide Cluster of Germanium

Heating a metastable solution of Ge^I Br to room temperature led to the first structurally characterized metalloid subhalide cluster Ge₁₄ Br₈ (PEt₃ )₄ (1). Furthermore 1 can be seen as the first isolated binary halide cluster on the way from Ge^I Br to elemental germanium, giving insight into the complex reaction mechanism of its disproportionation reaction. Quantum chemical calculations further indicate that a classical bonding situation is realized within 1 and that the last step of the formation of 1 might include the trapping of GeBr₂ units.

Targeted attachment of functional groups at Ge9 clusters via silylation reactions

A metalloid Ge clusters receives reactive substituents.

Synthesis and solid state structure of a metalloid tin cluster [Sn10(trip8)]

The Mg(i) compound (LMg)₂ reacts with (trip₂Sn)₂ with formation of the metalloid Sn₁₀trip₈ cluster 1, which contains Sn atoms in the formal oxidations states 0, +I and +II, while the stronger Mg(i) reductant (L′Mg)₂ yielded elemental tin. The reaction demonstrates the promising potential of Mg(i) compounds to serve as soluble reductants for cluster synthesis.