Uwe Hermann

Reaction pathways towards 1,1,2,2-tetratbutyldistannanes

Abstract 1,2-Dichlorotetratbutyldistannane (1) is synthesized as a byproduct in the reaction of tbutylmagnesium chloride with tin tetrachloride or by the reaction of ditbutyltindihydride with ditbutyltin dichloride in the presence of amines. Reaction of 1 with lithium aluminumhydride yielded the dihydrido derivative 2. The treatment of 2 with bromoform gave the dibromo distannane 3 nearly quantitatively. Reactions of 2 with one equivalent of LDA or KH yielded unsymmetrically substituted alkali metal distannanes of the type MtBu2SnSn(H)tBu2 (4, M=Li; 5, M=K). Reaction of either two equivalents of KH with 2, or one equivalent of KH with 5 gave the dipotassium distannide 6. The molecular structure of the dichloro derivative 1 was determined by X-ray diffraction.

Novel Si–Sn ring systems with distanna and tristanna moieties

Abstract The synthesis of new cyclic stannaoligosilanes 9, 10 and 11 with a bridging tin–tin unit [(tBu2Sn)2(SiMe2)n, n=2, 9; n=3; 10; n=4, 11] or an Sn3 moiety [(tBu2Sn)3(SiMe2)2] (12) are reported. All compounds are fully characterised by NMR, mass spectroscopy and elemental analysis. The structure of the five-membered ring 10 is determined by X-ray crystallography.

Cyclohexasilanes with exocyclic organogermanium, -tin or -lead groups

Abstract A new class of mono- ( 2 – 4 ) and bis(undecamethylcyclohexasilanyl) ( 5 – 9 ) substituted germanium, tin and lead compounds is described. These molecules are accessible by treatment of undecamethylcyclohexasilanyl potassium ( 1 ) with chlorogermanes, -stannanes or plumbanes. Attempts to generate bis(cyclohexasilanyl)methanes, -plumbanes or tris(cyclohexasilanyl)methylstannane starting from dihalomethanes, -plumbanes or methyltrichlorostannane and 1 result only in transmetallation reactions. The molecular structures of a mono- ( 3 ) and a dicyclohexasilanyl stannane derivative 5 were determined by single-crystal X-ray crystallography.

Reaction Pathways towards Novel Open Chain and Cyclic Stannasilanes

Cyclic stannasilaalkanes are formed by rearrangement reactions of open chain and branched Si-Sn derivatives. Furthermore, we report on first attempts towards three membered Si-Sn rings via lithio or potassio substituted stannanes.

On some reactions of undecamethylcyclohexasilanyl-substituted silanes

Abstract A number of undecamethylcyclohexasilanyl-substituted silanes have been prepared employing a salt elimination reaction between undecamethylcyclohexasilanyl potassium and several silyl halides or triflates. This method provides access to compounds with one or two undecamethylcyclohexasilanyl units attached to one silicon atom. Several attempts to introduce a third ring failed, resulting in formation of bis(undecamethylcyclohexasilanyl). An alternative approach to the substance class using silyl anions and undecamethylcyclohexasilanyl bromide was also developed. The molecular structure of bis(undecamethylcyclohexasilanyl)methylsilane was determined by X-ray crystallography.

Synthese und Reaktionsverhalten von Stannyloligosilanen, I. Kettenförmige Stannyloligosilane mit SiMe2-Einheiten/Synthesis and Reactivity of Stannyloligosilanes, I. Stannyloligosilane Chains Containing SiMe2 Moieties

Stannyloligosilanes 1 and 2 with terminal organotin groups are available by reacting alkali metal tri- or diorganostannides with α,ω-dichloro- or difluorosilanes, or by treatment of organochlorostannanes with α,ω-difluorosilanes in the presence of magnesium . Attempts to functionalize the triorganotin derivatives 2 by halogenation reagents did not result in the halogen compounds 5; instead cleavage of silicon-tin bonds is observed. In contrast, reactions of the hydridotin derivatives 1 with CHX3 (X = Cl, Br) lead to the quantitative formation of the bis(chloro- or bromostannyl)oligosilanes 5. A ll compounds were characterized by NMR, IR, MS and elemental analysis. In addition, the triorganotin compound 2i and the hydridotin species 1b have been characterized by X-ray crystallography.

Synthesis and reactivity of novel bis(stannyl)silanes

Bis(stannyl)silanes of types R3Sn-SiR′2-SnR3 and R2(H)Sn-SiR′2-Sn(H)R2 with R′ being methyl, phenyl, iso-propyl or terf-butyl have been synthesized by treatment of difunctionalized diorganosilanes with alkali stannides (R = Me, tBu; R′= Me, iPr; 1 - 6, 8 ) or with triphenyltin chloride and magnesium (R = Ph; R′ = Me, iPh;Pr; 7, 9). Me3Sn-SitBu2-SnMe3 4, was halogenated using SnCl4, to yield the bis(chlorostannyl)silane 11. The reaction of bis(stannyl)diorganosilanes R3SnSiR′SnR3 with catalytic amounts of Pd(PPh3)4 resulted in unexpected rearrangements under formation of the silyldistannanes R3SnSnR2SiR′R2. These compounds undergo addition reactions with alkynes. All compounds have been identified by NMR, IR, MS and elemental analysis. Compounds 5, 6 and 7 have also been characterized by X-ray crystallography.

New Silicon and Tin Containing Ring and Cage Compounds - Syntheses and Reactivity

The syntheses of new stannyloligosilanes starting from dichlorodi-organostannanes (R2SnCl2) and α,ω-difluoromethyloligosilanes with magnesium are described. Depending on the molar ratio of reactants and substituents R, cyclic or acyclic compounds are formed. X-ray structure of 4b and reactivity of the cyclic stannylsilanes are also reported.