Organotin polymer chemistry

A large number of studies on the polymerization and copolymerization of tin-containing monomers and the synthesis of new organotin polymers have been reported. In this review article the results are discussed and further ways for research in this interesting and important field of organometallic and polymer chemistry outlined. 

Recent survey articles 61,62) are mainly concerned with the synthesis, properties and applications of carbon-chain organotin polymers and with the use of organotin compounds in polymer chemistry as stabilizers, fungicides, etc. It should particularly be noted that polymers on the basis of trialkylstannyl methacrylates exhibit biocide properties. 

In recent reviews 85,86> are discussed the uses of organotin compounds as stabilizers and catalysts in polymer chemistry. 

The structural chemistry of the organotin halides is dominated by their Lewis acid properties and their propensity to form five- and six-coordinate complexes. Self-association may give oligomers or polymers in the solid state, which usually dissociate in solution. The structure of tricyclohexyltin chloride in the crystal is temperature-dependent. At 108 K, it has the form of a rod-like polymer with distorted trigonal-bipyramidal tin and Sn-Cl separations of 245.6(7) and 300.77(7) pm, but at 298 K, the structure is best regarded as consisting of near-tetrahedral discrete molecules.3... 

In 1951, Solerio reported that compounds with the R2SnO formula could be monomeric as well, when the tin atom carries bulky substituents, such as diorganylstannanones R2Sn=0, R = C12H25. When the substituents R are less bulky, the substrates are still polymers. Thus, Solerio can be considered as the founder of the chemistry of diorganylstannanones R2Sn=0, the first organotin compounds of three-coordinated tin, bonded to one of its substiments by a double bond. 

Tributyltin hydride is the most popular reagent in preparative free radical chemistry. The majority of the published work deals with the use of stoichiometric quantities, although alternative approaches such as catalytic or polymer-supported procedures have been developed. Occasionally other substituted organotin hydrides have been used, Ph3SnH being the most representative. 

The chemistry of catenated organotin compounds began as early as 1852 with the report by Ldwig 187) of the reaction of ethyl iodide with tin-sodium alloy. A product of this reaction, a diethyltin polymer, has only very recently been characterized 11,159,188). A similar situation may be cited in the case of tetrakis (triphenylstannyl) tin which was prepared as early as 1923 189), but was not rigorously identified until 1964 15,190). This compound is the only discrete branched-chain polytin in the literature at present. These two examples are not entirely representative of the state of the science in... 

Organotin compounds with Sn-S bonds can be prepared by substituation at tin by sulfur nucleophile. There are many parallels between the chemistry of compounds containing Sn-S bonds and those containing Sn-0 bonds. An important difference between them is that whereas Sn-0 bonded compounds often self-associate to give oligomers or polymers with 5-coordinate tin, the sulfur compounds show fewer tendencies to associate. The Sn-S bonds also less easily cleaved in substitution (e. g. hydrolysis) and addition reactions [54,56]. 

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