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.

Phosphine-Stabilized Digermavinylidene.

An intramolecular germylene-phosphine Lewis pair (1) was reacted with germanium dichloride to give in 92% yield a phosphine adduct of a chloro substituted germyl-germylene (2). After reduction of this dichloride with strong reductants like the Mg(I) reagent {(MesNacnac)Mg}2 (72% yield) or Na (52% yield) a phosphine stabilized digermavinylidene (3) was isolated as crystalline material [MesNacnac = {[(Mes)NC(Me)]2CH}-, Mes = 2,4,6-Me3C6H2]. The electronic structure of the digermavinylidene was investigated by density functional theory calculations. In reaction with adamantylphosphaalkyne the product of a [2+2] cycloaddition was characterized (4). Adamantylazide abstracts at room temperature a germanium atom from the digermavinylidene and a tetrameric organogermanium nitride (5) was isolated as colorless crystals.

Intramolecular Tetrylene Lewis Adducts: Synthesis and Reactivity.

A series of benzyl(diphenylphosphino) and o-phenyl(diphenlyphosphino) substituted germylenes and plumbylenes were synthesized by nucleophilic substitution between the respective lithium reagent and tetrylene halide. The Lewis pairs were characterized by X-ray crystallography and NMR spectroscopy. The reactivity of the tetrylenes was investigated with respect to azide addition. In the germylene case, the germaniumimide was formed as the kinetically controlled product, which rearranges upon heating to give the phosphinimide. The stannylene and plumbylene derivatives react with adamantylazide to give the azide adducts. 1-Pentene reacts diastereoselectively with the phosphagermirane to give a cyclic addition product. Trimethysilylacetylene shows an addition with the benzylphosphino-substituted germylene and plumbylene to give the cycloheteropentene molecules. The addition product between phenylacetylene and the four membered Ge-P adduct shows after addition at room temperature a 1,4-phenylmigration to give a cyclic phosphine. Alkylnitrene insertion into a Ge-C bond of the alkyne addition product of the phosphagermirane was found in reaction with adamantylazide.

η(3) -Allyl coordination at tin(II)-reactivity towards alkynes and benzonitrile.

We herein report the synthesis and characterization of a terphenyl-substituted Sn(II) allyl compound featuring an η(3)  coordination mode in solution and in the solid state. Two examples for the interesting reactivity of the allyl Sn(II) molecule are presented: Reactions with terminal alkynes result in the formation of tricyclic compounds by CC bond formation and the dimerization of two Sn moieties whereas the reaction with benzonitrile leads to a sixteen-membered ring system through CH activation.

Chemistry of stannylene-based Lewis pairs: dynamic tin coordination switching between donor and acceptor character.

The coordination chemistry of cyclic stannylene-based intramolecular Lewis pairs is presented. The P→Sn adducts were treated with [Ni(COD)2] and [Pd(PCy3)2] (COD = 1,5-cyclooctadiene, PCy3 = tricyclohexylphosphine). In the isolated coordination compounds the stannylene moiety acts either as an acceptor or a donor ligand. Examples of a dynamic switch between these two coordination modes of the P-Sn ligand are illustrated and the structures in the solid state together with heteronuclear NMR spectroscopic findings are discussed. In the case of a Ni(0) complex, (119)Sn Mössbauer spectroscopy of the uncoordinated and coordinated phosphastannirane ligand is presented.