Distannanes preparation

Distanna-[4]ferrocenophane, alkyne addition, 10, 748 Distannanes, preparation, 3, 856... 

Catenation is well established in organotin chemistry and distannane derivatives can be prepared by standard methods (see Ge, p. 396). The compounds are more reactive than organodiger-manes e.g. Sn2Meg (mp 23°) inflames in air at its bp (182°) and absorbs oxygen slowly at room temperature to give (Me2Sn)20. Typical routes to higher polystannanes are ... 

Transient dialkylstannylene intermediates R2Sn (reviewed in ref. 333) can be prepared by the thermolysis of distannanes ClR2SnSnR2Cl, R3SnSnR2Cl, or HR2SnSnR2H, e.g., (334, 335)... 

Using alkyllithium compounds, a distannane with a very long Sn—Sn bond, 3.03A, and a syw-peripheral conformation122 was prepared. Thus, reaction of di-t-butyl(chloro)2,4,6-triisopropylphenyl)tin, 78, with f-butyllithium gives 1,1,2,2-tetra-f-butyl-l,2-(2,4,6-triisopropylphenyl)ditin, 79, which displays a restricted rotation about the Sn—C bond as well as the Sn—Sn bond, even at high temperatures. 

Hexabutyldistannane, which is an important reagent in many organic syntheses, can be prepared very conveniently by reducing bis(tributyltin) oxide with sodium borohydride in ethanol at room temperature. After 5 min, the only tin species present is tributyltin hydride, but in 2 h, its decomposition is catalyzed by the ethoxide ion that is formed to give the distannane in 83% yield.444 Hexaalkyldistannanes, R3SnSnR3 (R = Et, Pr, or Bu), are obtained in ca. 50% yield when the corresponding trialkyltin halides are treated with zinc powder in THF.445... 

Most of the reactions that can be used to prepare distannanes can be extended to the preparation of oligo- and polystannanes, which have attracted interest for potential use in electronic and optical devices.455 The structures of the products are not necessarily those of completely linear catenanes, (R2Sn) , and different degrees of branching confer different properties. The formation of polymers is also frequently accompanied by the formation of cyclic pentamers or hexamers, and samples prepared by different methods may show substantially different properties. 

Another entry into the preparation of 3-arylpyrroles starts with the reaction of the 3-iodopyrrole derivative shown in 6.28. with hexabutyl-distannane in the presence of a palladium catalyst. The formed intermediate was reacted, in the presence of a similar catalyst system, with different aryl iodides to give the desired products in good to excellent yield38 It is worth mentioning that the presence of a formyl group in the 2-position of he pyrrole had no adverse effect on the efficiency of the couplings. 

The one-step preparation of y-butyrolactones starting from an acyclic a-iodo ester was also investigated by using the polymer-supported distannane 90 as radical source. The y-butyrolactone was formed in 35% yield and contained 61% of the reduced a-haloester166 (Scheme 45). 

In addition to the general methods shown in Scheme 1 for the construction of Sn-Sn bonds, a number of distannanes have been obtained by a variety of other routes, most of which were initially discovered serendipi-tously (Scheme 2). For instance, in an attempt to prepare tetra(t-butyl)stan-nane (3) from tri(r-butyl)tin chloride (4), Kandil and Allred (17) found... 

C into distannanes and Hg. The compound (PhjSn)2Hg prepared by Eq. (a) is more stable thermally, decomposing at 20°C, but crystalline (t-Bu3Sn)2Hg melts at 196°C (see Table 1). When Et2Hg is used instead of t-BujHg as in Eq. (a), only decomposition occurs. ... 

Commonly, the metal M is lithium, when the reagents have been described as stannylanionoids. These reagents can readily be prepared from the tin halides and metallic lithium (equation 4-27), or the distannanes and an alkyllithium (equation 4-28), or the tin hydrides and LDA (equation 4-29) (see Section 19.1.1). 

Stannylpyrimidines have been prepared from the reaction of halogenopyrimidines with stannylhthium or stannylsodium reagents (e.g. equation 7-27),96 and again, by analogy with the homoarylstannanes, the heteroarylstannanes can be made from the heteroaryl halide and a distannane with a palladium catalyst (equation 7-28).97... 

A number of stannacycloalkanes have been prepared which contain an Sn-Sn bond, but these compounds show principally the characteristics of distannanes, and are considered in Section 18.4. 

The two principal routes to the organotin peroxides involve substitution by a peroxide nucleophile at a tin centre (equations 14-69 and 14-70), or (pericyclic) reaction of an allyltin compound with singlet oxygen (equation 14-71). Distannyl peroxides have also been prepared by the (homolytic) reaction of distannanes with triplet oxygen (equation 14-72). 

Stannyl hydroperoxides and distannyl peroxides are probably formed in homolytic chain reactions when triplet oxygen reacts with tin hydrides or distannanes, respectively, but the peroxide products are rapidly reduced by the reactants and these reactions are not useful preparatively. 

Hexaaryldistannanes with bulky ort/zo-substituted phenyl groups are in thermal equilibrium with the corresponding triarylstannyl radicals, which can be detected by ESR spectroscopy. These distannanes consequently can be prepared by abstracting hydrogen from the corresponding triarylstannanes (Section 18.2.3).4... 

In a related reaction, hexakis(2-cyanoethyl)distannane, (NCCH2CH2)3SnSn(CH2CH2CN)3, can be prepared in 50% yield by the electrolysis of an aqueous alkaline solution of acrylonitrile with a sheet tin cathode and platinum gauze anode.32,33... 

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