Molecular Ln(III)-H-E(II) Linkages (Ln=Y, Lu; E=Ge, Sn, Pb).

Following the alkane-elimination route, the reaction between tetravalent aryl tintrihydride Ar*SnH and trivalent rare-earth-metallocene alkyls [Cp* Ln(CH{SiMe } )] gave complexes [Cp* Ln(μ-H) SnAr*] implementing a low-valent tin hydride (Ln=Y, Lu; Ar*=2,6-Trip C H , Trip=2,4,6-triisopropylphenyl). The homologous complexes of germanium and lead, [Cp* Ln(μ-H) EAr*] (E = Ge, Pb), were accessed via addition of low-valent [(Ar*EH) ] to the rare-earth-metal hydrides [(Cp* LnH) ]. The lead compounds [Cp* Ln(μ-H) PbAr*] exhibit H/D exchange in reactions with deuterated solvents or dihydrogen.

Reductive Elimination and Oxidative Addition of Hydrogen at Organostannylium and Organogermylium Cations.

Bulkily substituted organodihydrogermylium and -stannylium cations [Ar*EH ] (E=Ge, Sn; Ar*=2,6-Trip C H , Trip=2,4,6-triisopropylphenyl) were characterized as salts of the weakly coordinating perfluorinated alkoxyaluminate anion [Al{OC(CF ) } ] . At room temperature, the stannylium cation liberates hydrogen to generate the low valent organotin cation [Ar*Sn] . In contrast, the dihydrogermylium cation transfers the hydrogen atoms to an aryl moiety of the terphenyl ligand and oxidatively adds either hydrogen under an atmosphere of hydrogen or a sp CH unit of the 1,2-difluorobenzene solvent.

Reductive Dehydrogenation of a Stannane via Multiple Sn-H Activation by Frustrated Lewis Pairs.

A bulky substituted stannane Ar*SnH (Ar*=2,6-(2',4',6'-triisopropylphenyl)phenyl) was treated with the well-known frustrated Lewis pair (FLP) PtBu /B(C F ) in varying stoichiometries. To some degree, hydride abstraction and adduct formation is observed, leading to [Ar*SnH (PtBu )] which is rather unreactive toward further dehydrogenation. In a competing process, the FLP proved to be capable of completely striping-off hydrogen and hydrides to generate the first cationic phosphonio-stannylene [Ar*Sn(PtBu )] .

Cationic Stannylenes: In Situ Generation and NMR Spectroscopic Characterization.

The reaction of NHC (NHC = 1,3,4,5-tetramethylimidazolylidene, where NHC = N-heterocyclic carbene) adducts to organotin(II) hydrides Ar*SnH and Ar'SnH [Ar* = 2,6-TripCH, where Trip = 2,4,6-triisopropylphenyl; Ar' = 2,6-MesCH, where Mes = 2,4,6-trimethylphenyl)] with Lewis acids such as B(CF) or [CPh] allows the abstraction of hydride and thus the generation of cationic, dicoordinate bis(σ-C)-substituted stannylenes [ArSn(NHC)]. The supposedly dicoordinate constitution of this cationic stannylene was investigated by NMR spectroscopy and further supported by density functional theory computations. For Ar'SnH(NHC), the generated cation was found to be inadequately sterically encumbered, allowing the formation of an adduct, [Ar'(NHC)Sn-Sn(H)(NHC)Ar'], which can be described as the protonated bis(NHC) adduct to the formal 1,2-distannyne.

Reductive Elimination of Hydrogen from Bis(trimethylsilyl)methyltin Trihydride and Mesityltin Trihydride.

Alkyltin trihydride [(Me Si) CHSnH ] was synthesized and the reductive elimination of hydrogen from this species was investigated. A methyl-substituted N-heterocyclic carbene reacts with the organotrihydride in dependence on stoichiometry and solvent to give a series of products of the reductive elimination and dehydrogenative tin-tin bond formation. Besides characterization of the carbene adduct of the alkyltin(II) hydride, a Sn chain was also isolated, encompassing two stannyl-stannylene sites, which are stabilized each as NHC-adducts.

Access to Base Adducts of Low-Valent Organotin-Hydride Compounds by Controlled, Stepwise Hydrogen Abstraction from a Tetravalent Organotin Trihydride.

Hydrogen can be selectively removed from organotin trihydrides to generate the corresponding organohydrostannylene intermediates. Depending on the size of the substituent and the mode of generation, the intermediates undergo further reactions. Herein, we report on the formation of a variety of organotin hydrides with tin in the oxidation states Sn(II) , Sn(I) -Sn(III) and Sn(III) -Sn(III) , all accessed by the controlled removal of hydrogen from the tetravalent Ar'Sn(IV) trihydride (Ar'=2,6-dimesitylphenyl, mesityl=2,4,6-trimethylphenyl).