Tin chemistry

I. A. ZUBiETA and I. I. Zuckerman, Structural tin chemistry, Prog. Inorg. Chem. 24, 251-475 (1978). An excellent comprehensive review with full structural diagrams and data, and more than 750 references. 

Application of ll5Sn chemical shifts to structural tin chemistry. P. J. Smith and L. Smith, Inorg. Chim. Acta, Rev., 1973, 7,11-33 (73). 

In contrast to the transition metals, where there is often a change in oxidation level at the metal during the reaction, there is usually no change in oxidation level for boron, silicon, and tin compounds. The synthetically important reactions of these three groups of compounds involve transfer of a carbon substituent with one (radical equivalent) or two (carbanion equivalent) electrons to a reactive carbon center. Here we focus on the nonradical reactions and deal with radical reactions in Chapter 10. We have already introduced one important aspect of boron and tin chemistry in the transmetallation reactions involved in Pd-catalyzed cross-coupling reactions, discussed... 

Evaluation of the above route against our initial target objectives for the synthesis of taranabant indicated a high level of success, not just for the primary objectives of removing the tin chemistry and chiral chromatography, but for a number of other process improvements (Table 9.2). Of particular note was that the three crystalline intermediates were key for purification, first the phenethylamine salt 12 for the classical resolution, secondly the HC1 salt of amine 2 allowed for upgrade of diastereomeric purity, and finally the API allowed for upgrade of enantiomeric purity via initial removal of racemic material. 

This area of tin chemistry has expanded greatly as many new compounds have been synthesized and characterized. One of the most unusual compounds of this type is Sn6H10, which has the structure... 

Disproportionation reactions are well known in tin chemistry and can account for the occurrence of several methyltin compounds, assuming a methyltin species was present in the first place. Similarly, transmethylation can occur between inorganic tin species and methylated forms of other elements. Examples of this nature, some of which may take place in water, are given in Section V, Reference 2. Their environmental significance is unknown. Disproportionation reactions are also covered in Section V, Reference 1. A general theory of methylation by MeCoBn was proposed, based on redox potentials51. 

The oxidation of the methyl radicals formed by DMTC pyrolysis is well understood compared with the tin chemistry. Gas-phase mechanisms describing this chemistry are readily available [61-63]. These reactions lead to the formation of other reactive species that can attack DMTC, including H, O, OH, and HO2. The OH radical in particiflar is a very efficient H-abstractor, and will therefore quickly react with DMTC ... 

The results presented here show that quantum-chemistry methods, whose accuracy and sophistication continue to increase, are capable of providing thermochemical data of practical value for modehng organometallic tin chemistry. In particular, the relativistic effective core potential used here appears to provide an adequate description of the electronic structure at tin, based on the favorable comparisons between experimental heats of formation and values predicted by the ECP/BAC-MP4 method. Trends in heats of... 

Zirconaindenes, which are easily obtained by insertion of various alkynes or an ynamine into the Zr—C bond of in situ generated99 100 benzyne-zirconocene, are very good precursors of 1,1-dichloro-l-germaindenes (90) (Scheme 16)101. This method has been successfully extended to tin chemistry (Scheme 17)102. In this case, a convenient reaction was obtained even with alkyl or aryltrichlorostannane. 

Regioselective reactions in systems which contain multiple functional groups are an area ideally suited for biocatalysis. Linhardt and co-workers at the University of Iowa s Division of Medicinal and Natural Products Chemistry recently published the synthesis of a series of 1 -O-acyl sucrose derivatives [31], Using Chiro-CLEC -BL (the CLC of subtilisin) and vinyl esters of the acylating agent in pyridine as solvent, the authors prepared l -O-lauryl sucrose, l -O-myristyl sucrose, and l -O-stearyl sucrose in 80-90% yield (Fig. 9). Their method represents a green alternative to the tin chemistry previously used [32],... 

In tin chemistry, this type of reaction was used to prepare a distannacyclooctane, but in low yield (11%) (equation 112)140. 

The same reaction was observed in tin chemistry (equation 121)4b and applied also to the synthesis of a tin-zinc compound (equation 122)4b. 

These 1,4-additions were also observed in tin chemistry (equations 167 and 168)176 179... 

Many organolithium compounds are useful reagents and no doubt many more would be if only they could be made. Tin chemistry allows us to make organolithium compounds that cannot be made by direct lithiation. 

However, the problem should be easily solved with tin chemistry. The idea is to add a tributyltin lithium reagent to the aldehyde, mask the alkoxide formed, and then exchange the tributyl tin group for lithium. 

Gielen, M., Panell, K., Tiekink, E. (2008). Tin Chemistry Fundamentals, Frontiers, and Applications. 

Mossbauer spectroscopy has proved to be a very valuable tool in tin chemistry. The isomer shift (IS) is a measure of the 5s electron density at the tin nucleus while the quadrupole splitting (QS) is a measure of the electric field gradient (due to the asymmetry of the electron cloud) at the tin nucleus. On going from the plus two to the plus four oxidation state tin loses 5s electron density. Since the tin nucleus expands on absorption of the 23.9 keV photon during the Mossbauer experiment, the greater the s electron density at the nucleus the more positive the isomer shift will be (56, 57). Therefore, tin(II) compounds have higher isomer shift values than do tin(IV) compounds. The isomer shift of /3 tin (2.56 mm/sec relative to BaSnOa) is commonly used as the dividing point between divalent and tetravalent tin (58-60). 

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