Three-membered cyclic digermylenes stabilised by an N-heterocyclic carbene

Aluminagerma[5]pyramidanes-Formation and Skeletal Rearrangement

The salt metathesis reaction of dipotassium germacyclopentadienediide with aluminum(III) dichlorides provides either half-sandwich alumole complexes of germanium(II) or aluminylene germole complexes. Their molecular structure and the delocalized bonding situation, revealed by density functional theory (DFT) calculations, are equally described as isomeric aluminagerma[5]pyramidanes with either the germanium or the aluminum atom in the apical position of the pentagonal pyramid. The product formation and the selectivity of the reaction depends on the third substituent of the aluminum dichloride. Aryl-substituents favor the formation of alumole complexes and Cp*-substituents that of the isomeric germole complexes. With amino-substituents at the aluminum atom mixtures of both isomers are formed and the positional exchange of the two heteroatoms is shown by NMR spectroscopy. The alumole complexes of germanium(II) undergo facile reductive elimination of germanium and form the corresponding alumoles.

Synthesis, Characterization, and Reaction of Digermylenes

A series of digermylenes R(EGeL)₂ (L=CH[C(Me)N(Ar)]₂, Ar=2,6‐iPr₂C₆H₃; E=O, R=1,3‐C₆H₄ (1), 1,4‐C₆H₄ (2), Me₂C(CH₂)₂ (3); E=NH, R=1,4‐C₆H₄ (4), 1,4‐C₆H₁₀ (5); E=C(O)O, R=1,3‐C₆H₄ (6)) were synthesized by the reactions of L′Ge (L′=HC[C(CH₂)N(Ar)]C(Me)N(Ar), Ar=2,6‐iPr₂C₆H₃) with selected diphenols, diol, diamines, and o‐/m‐phthalic acids, respectively. Treatment of digermylene 1,3‐C₆H₄(OGeL)₂ (1) with sulfur, selenium and CuX (X=Cl, Br, I) led to the formation of 1,3‐C₆H₄[OGe(S)L]₂ (8), 1,3‐C₆H₄[OGe(Se)L]₂ (9), and (CuX)₂[1,3‐C₆H₄(OGeL)₂]₂ (X=Cl (10), Br (11), I (12)), respectively. The obtained products were characterized by melting point, elemental analysis, FT‐IR, ¹H and ¹³C NMR spectroscopy, and single‐crystal X‐ray diffraction.

Introduction of plumbole to f-element chemistry

Herein, we present the synthesis and characterization of heteroleptic lanthanide complexes bearing a dianionic η5-plumbole ligand in their coordination sphere. The reaction proceeds via a salt elimination reaction between the dilithioplumbole ([Li(thf)]2[1,4-bis-tert-butyl-dimethylsilyl-2,3-bis-phenyl-plumbolyl] = [Li2(thf)2(η5-LPb)]) and specifically designed [Ln(η8-COTTIPS)BH4] precursors (Ln = lanthanide, La, Ce, Sm, Er; COTTIPS = 1,4-bis-triisopropylsilyl-cyclooctatetraenyl), that are capable of stabilizing a planar plumbole moiety in the coordination sphere of different trivalent lanthanide ions. In-depth ab initio calculations show that the aromaticity of the dianionic plumbole is retained upon coordination. Electron delocalization occurs from the plumbole HOMO to an orbital of mainly d-character at the lanthanide ion. The magnetic properties of the erbium congener were investigated in detail, leading to the observation of magnetic hysteresis up to 5 K (200 Oe s-1), an unequivocal proof for single molecule magnet behavior in this system. The magnetic behavior of the erbium species can be modulated by manipulating the position of the lithium cation in the complex, which directly influences the bonding metrics in the central [(η5-LPb)Er(η8-COTTIPS)]- fragment. This allowed us to assess a fundamental magneto-structural correlation in an otherwise identical inner coordination sphere.

Transmetalation Reactions of Aromatic Dilithionickelole: Synthesis of Heterobimetallic Complexes Featuring Metalloles as Diene Ligands

The aromatic metallole dianions are important metallaaromatic compounds because of their various reactivities and extensive synthetic applications. Herein we report the reactions of dilithionickelole with MgCl₂ , EtAlCl₂ , Cp*ScCl₂ , Cp*LuCl₂ and Pt(COD)Cl₂ (COD=1,5-cyclooctadiene) affording a series of Ni/M heterobimetallic complexes of the general formula (η⁴ -C₄ R₄ M)Ni(COD), in which the metalloles act as diene ligands, as suggested by single-crystal X-ray, NMR and theoretical analyses. In these reactions, two electrons of the nickelole dianion transferred to Ni, representing different reactivity compared with main-group metallole dianions.

Radicals and Anions of Siloles and Germoles

The synthesis of persistent sila- and germacyclopentadienyl (silolyl- and germolyl-) radicals by careful stoichiometric reduction of the corresponding halides with potassium is reported. The radicals were characterized by EPR spectroscopy and trapping reactions. The reduction of tris(trimethylsilyl)silyl-substituted halides was successful while smaller substituents (i. e., t-Butyl, Ph) gave the corresponding dimers. The EPR spectroscopic parameter of the synthesized tetrolyl radicals indicate only small spin delocalization to the butadiene unit due to cross-hyperconjugation. Silolyl- and germolyl anions are unavoidable byproducts and are isolated in the form of their potassium salts and characterized by X-ray crystallography. The comparison of the molecular structures of two closely related potassium silolides provided an example for different coordination of the potassium cation to the silolyl anion (η1 vs. η5 coordination) that triggers the switch between delocalized and localized states.

Phosphine-Stabilized Germasilenylidene: Source for a Silicon-Atom Transfer

A phosphine-stabilized germasilenylidene is synthesized following the pathway of SiCl₄ oxidative addition at a germylene-phosphine Lewis pair. Low-temperature reduction using {(^MesNacnac)Mg}₂ resulted in a chlorosilylene intermediate and finally a molecule exhibiting a Ge═Si: motif. Inside the chelating phosphine-germylene, a low-valent silicon atom is stabilized and was transferred to diazabutadiene to give N-heterocyclic silylenes. Because of the high reactivity of the phosphine-stabilized germasilenylidene, a reaction of two Ge═Si: units was found to yield a Si₂Ge₂-ring molecule exhibiting a germasilene substituted with a silylene.