Diorganotin Carboxylates

Commeicial grades of diorganotin carboxylates frequendy have wider melting ranges because of the use of less pure grades of carboxylic acids in their manufacture which, for many apphcations, permits mote facile handling of the hquids. 

On partial hydrolysis, diorganotin halides and carboxylates may form basic salts having a rather comphcated stmcture ... 

Dibutyltin and dioctyltin diacetate, dilaurate, and di-(2-ethylhexanoate) are used as catalysts for the curing of room-temperature-vulcanized (RTV) sihcone elastomers to produce flexible siUcone mbbers used as sealing compounds, insulators, and in a wide variety of other appHcations. Diorganotin carboxylates also catalyze the curing of thermosetting siHcone resins, which are widely used in paper-release coatings. 

Diphenic acid (H2A) also forms diorganotin(IV) complexes, which are with two monodentate -COO groups. On the other hand, soluble dinuclear triorganotin(IV) complexes (where the organo moieties are Me and Ph) contain symmetrically bound carboxylates, while the less-soluble compound (cHexsSn) has two asymmetrically bonded carboxylates. All have Tbp structures with [RsSnirV)] units remote from each other. °... 

Different synthetic routes were developed to prepare distannoxane carboxylates. Two methods commonly used are (i) the reaction of diorganotin oxides with carboxylic acids under azeotropic removal of water and (ii) the hydrolysis of diorganotin dicarboxylates. Diorganotin dicarboxylates are highly moisture-sensitive... 

Triorganotin carboxylates may exist in monomeric or polymeric forms, while diorganotin derivatives may exist as true dicarboxylates or as distannooxane salts [(R2SnO-COR )20] and may further aggregate in a number of ways that influence both solubility and bioavailability. More work on the molecular basis for the activity of tin complexes is needed. 

Dioiganotin dihalides are moderately strong Lewis acids and form stable complexes with ammonia and amines. The commercially important diorganotin compounds are most frequently the oxides, carboxylates, and mercaptocarboxylic acid esters. The oxides are amorphous or polycrystalline, highly polymeric, infusible, and insoluble solids. They are moderately strong bases and react readily with a wide variety of strongly and weakly acidic compounds. Their insolubility in all nonreactive solvents makes the choice of proper reaction conditions for such a neutralization reaction an important consideration for optimum yields. 

TABLE 4. Minimum inhibition concentrations (MIC, mmoll ) of diorganotin chlorides and carboxylates ... 

Functionally substituted metallostannoxanes (M = Si, Ge, Pb, Tl, Hg X = halogen or carboxylate) can also be prepared by reaction between the appropriate metal halide MX and diorganotin oxide R2SnO (e.g. equation 12-31). Little is known about the structures and reactions of these compounds.143... 

In dimethyltin diformate, however, the two carbonyl groups bridge intermolecularly, to form infinite sheets similar to those in dimethyltin difluoride or dimethyltin di(fluorosulfonate).29 If the linearly polymeric diorganotin carboxylates are dissolved in chloroform, the 119Sn NMR chemical shift moves downfield by 50 to 100 ppm, and is then almost independent of concentration, showing that the compounds are monomeric in solution.23-30 Dibutyltin glutarate is a linear polymer as shown in 13-9.31... 

The hydrides R2SnHX (X = e.g. halide, carboxylate, sulphonate, alkoxyl) can be formed by the comproportionation between diorganotin dihydrides, R2SnH2, and the compounds R2SnX2. 

The simplest of the diorganotin carboxyiates are the dicarboxylates of the type R2Sn(O2CR02- These compounds are formed in a 1 2 reaction between an organotin substrate such as [R2SnO] and a carboxylic acid R C02H. In general, these have monomeric structures. The tin is hexacoordinate. 

Some trinuclear clusters are also known among diorganotin carboxylates. These are summarized in Table 2.4.2. It can be seen that the carboxylic acids involved in the formation of these compounds are mono/dicarboxylic acids containing other heteroatoms (Table 2.4.2, entries 1-5, 8 and 9) or dicar-boxylic acids without other heteroatoms (Table 2.4.2, entries 6 and 7). Among the cyclic compounds. 

Recently, there have been reports on other macrocyclic compounds involving diorganotin carboxylates. " Some examples are shown in Figure 2.4.5. A 48-membered macrocycle containing 18... 

Table 2.4.1 Representative examples of diorganotin carboxylates, [(R2Sn02CR )20]2 [Ladder types /. to...

Figure 2.4.7 One- and two-dimensional polymers formed among diorganotin carboxylates ...

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