Organotin/halides

Covalent Organotin Halide, Pseudohalide, Carboxylate, and Nitrate Complexes 

Organotin halides are versatile reagents for which many derivatizing schemes can be devised. Trace analysis of organotin componds in environmental samples often involve halostannanes, as was discussed in Section in. 

The synthesis of organotin halides is of paramount importance for organotin chemistry, because these compounds are considered as the starting materials for the preparation of a great number of organotin substances. 

Organotin enamines can be prepared by treating organotin halides with the lithium or magnesium derivatives of enamines, and also by treating distannazanes with tin enolates (222,223). 

Other syntheses of functional organotin halides include that of /J-chlorovinyltin compounds330  

An application of the reduction method of organotin halides by simple organotin hydrides is the preparation of l, >-bis(hydridodimethylstannyl)alkanes235  

The oldest method for the synthesis of the organotin halides is the reaction of alkyl or aryl halides with elemental tin. This reaction exhibits numerous variants and uses a wide variety of catalysts however, yields are usually unsatisfactory and the method is no longer common nowadays. 

Perfluorovinyl organotin compounds can be prepared from perfluorovinyl Grignard reagents and organotin halides [76] (equation 11) Yields are slightly improved under Barbier conditions [76] 

A very versatile preparation seems to be the elimination of organotin halides in the reaction of organostannyl-organosilylcyclopentadienes with metal carbonyl halides. This reaction is very selective and only Sn—C bonds are cleaved with formation of 7)5-cyclopentadienyl complexes (7)  

Fig. 13.10 Chromatogram of hydrides generated from a known mixture of Sn(IV) and nine organotin halides 

Reaction conditions Aqueous solutions of cotton (0.100 g 0.62 moles) with bisethylenediamine copper (II) hydroxide to give 25 ml solution are added to rapidly stirred (about 20,500 rpm no load) carbon tetrachloride (25 ml) solutions containing the organotin halide at about 25°C, 30 secs stirring time. 

Redistribution reactions are considered as quite important for the preparation of alkyltin halides having mainly identical alkyl groups. Actually, the redistribution reactions are halogenation reactions of organotin halides by SnX4 (X = F, Cl, Br, I). 

Dimethyltin dichloride can be synthesized from methyl chloride, tin(II) chloride and molten tin. The reaction proceeds in high yields in NaAlCLt melt359. High yields in tri-organotin halides are also obtained from tin and lower alkyl halides, provided an equimolar amount of halide is added to the reaction medium360. 

The alkylation of tin tetrachloride with organolithium compounds, Grignard reagents, or organoaluminum compounds remains the most common route to tetraalkyltins, and thence, by the Kocheshkov disproportionation, to the various organotin halides. 

The most substantial study of this sort, analysing structures of 186 four-, five- and six-coordinated tin compounds, was published by Britton and Dunitz (1981) under the memorable title Pathways for SN2 and SN3 Substitution at Sn(IV) . Organotin halides readily increase their coordination number to 5 or 6 (Davies and Smith, 1982), and a wide range of structures are stable in the solid state. 

The opportunity of employing various electrophiles and functionalized diene precursors greatly enhances the synthetic potential of p3-allyltitanocenes. Besides aldehydes and ketones, carbon dioxide [11,15,16], acid chlorides [17], imines [11], nitriles [11], isocyanides [11], and organotin halides [18] react to afford the corresponding allylated products after hydrolysis. Examples are given in Scheme 13.8. 

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