Reactions distannenes

Disiloxane, tetramesityl-, 3,206 Disproportionation iridium catalysts, 4,1159 Dissolution nuclear fuels, 6, 927 Distannene, 3,217 Distannoxane, 1,3-dichloro-, 3,207 Distibine, tetraphenyl-, 2,1008 Distibines, 2,1008 Disulfido ligands metal complexes, 2,531-540, 553 bonding, 2, 539 electron transfer, 2, 537 intramolecular redox reactions, 2,537 reactions, 2, 537... 

The synthesis of doubly bonded tin compounds by the coupling of stannylenes, however useful, is limited by the need for a stable stannylene and often a second divalent species (for example, a carbene or isonitrile). The simplest example of this reaction is the formation of tetrakis[bis(tri-methylsilyl)methyl]distannene from two molecules of the corresponding stannylene,83 with which it is in equilibrium in solution as evidenced by NMR spectroscopy.91... 

Distannenes are in equilibrium with the corresponding stannylenes in solution therefore, reaction with alkynes can lead either to stannacyclo-propene or l,2-distannacyclobut-3-ene derivatives. Reaction of tetra-... 

Similar reactions were performed earlier photochemically from 76, which can be converted into tetrakis(2,4,6-triisopropylphenyl)distannene. 

New distannenes linked through phenylene, biphenylene, or thiophene spacers have been prepared by reactions of the type shown in Equation (175) (Cp =pentamethylcyclopentadienyl),541 and the ansa-stannocene (Equation (176)) is formed in low yield when dimethylfulvene reacts with tin vapor.542... 

Tetrakis(triisopropylphenyl)distannene (21-33) is obtained as an intense red solid by the photolysis or thermolysis of hexakis(triisopropylphenyl)tristannane, by way of the intermediate stannylene which can be trapped with 1,3-dienes or 1,2-diones (see Section 21.1.2) the photolytic conversion is quantitative at -78 °C. In solution at 0 °C, the stannylene slowly reverts back to the the cyclotristannane. The X-ray crystal structure has not yet been determined, but the molecule is believed to be twisted with little pyra-midalisation.68 The distannene reacts with phenylacetylene to give the distannacyclobu-tene, with rSnSn 284.0(1) pm. The distannenes 21-35 and 21-36 are formed in the disproportionation reaction shown in equation 21-10. 

Alkylation or arylation of stannous chloride gives stannylenes, RaSn , which normally self react to give linear or cyclic oligomers, but if the R groups are very bulky (t-butylphenyl, or 2,6-bis(2,4,6-tri-isopropylphenyl)phenyl), kinetically stable stannylenes can be obtained (see Chapter 2.8). In the solid state, the stannylenes usually dimerize to give the distannenes, R 2Sn=SnR 2, where R denotes a bulky group. Reaction of a stannylene with a carbene gives a stannene, R 2Sn=CR2. 

The syntheses of distannenes are generally achieved by the dimerization of stannylenes (see Section 2.8). As a unique example, distannene 6 is obtained by the thermal or photochemical reaction of tristanna-cyclopropane IS. It was reported that distannene 6 exists in equilibrium between 6 and 18, or stannylene 19 depending on the temperature (Scheme 2.9.3). In addition, the cyclic distannene 17 is obtained as a result of isomerization of tristannaallene 21 (see below). 

Except for 14, the reactivity of acyclic distannenes reflecting the Sn=Sn double-bond character has not been investigated because of their equilibrium in solution, and these distannenes react as the stannylene in many cases (see Section 2.8). Although some [2-1-2]-cycloaddition reactions were reported (Scheme 2.9.4),these cycloadducts could be formed either by [2-1-2]-cycloaddition or via the insertion of the second stannylene unit into the initially formed three-membered ring compound. 

Recently, a striking distannene, prepared from the reaction of Bu MeSiNa and SnCB (dioxane) in tetrahydrofuran... 

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