Dialkyltin compounds reactions

It should be noted that dicyclopentadienyltin does not give any detectable reaction with 2,3-dimehtyl-1,3-butadiene, in contrast to the dialkyltin compound 154). According to Eq. (31) 6- or 9-membered ring compounds are formed. The dicyclopentadienyl compound in Eq. (31) can also be replaced by the unstable stannylens 154). 

Early attempts at producing dialkyltin compounds yielded polymers. More recently, Neumann has found several synthetic routes to reactive R2Sn intermediates which can be trapped by oxidative-addition reactions (J). In the absence of trapping agents the divalent tin compound polymerizes. Lappert and co-workers have shown that the bulky bistri-methylsilylmethyl ligand stabilizes the divalent tin species toward polymerization. This stable divalent tin species thus provides an excellent starting material for investigating a wide variety of oxidative-addition reactions, as shown in Fig. 10 (78). 

Dialkyltin Compounds. All of the dialkyltin dimercaptides and dicarboxylates were prepared by reaction of the appropriate dialkyltin oxide (Alfa Inorganics) with the desired mercaptan or carboxylic acid. The reactions were carried out in refluxing benzene or toluene using a Dean-Stark water separator. The yields are quantitative and products require no purification (purity confirmed by H and 13C NMR). The dialkyltin dichlorides were obtained commercially (Alfa Inorganics) and used as received ... 

Stannyllithium compounds are important as sources of nucleophilic stannyl anions, and the dialkyltin lithium hydrides, R2SnLiH, have recently come to prominence as their reaction with electrophilic alkyl halides gives hydrides, R1R2SnH, with mixed alkyl groups (see Section 3.14.18.1).397... 

Catalysts Catalysts are widely used for PU manufacture. Sometimes a combination of two or three catalysts is required to obtain the desired balance of reaction rates between compounds of differing active hydrogen activity. Metal compounds, especially organotin compounds, are much more efficient catalysts than tertiary amines for the -OH/NCO reaction. In addition to more commonly used dibutyltin(IV) dilaurate, dibutyltin(IV) diacetate, dialkyltin(IV) oxide or salts of divalent fin with a variety of carboxylic acids such as stannous octoate, hexoate and naphthenate etc. are available for this purpose. Combination of tin catalysts with tertiary amines has been reported to lead to a synergistic increase in catalytic activity. 

Diorganotin(iv) derivatives of diphenic acid 233 were prepared by reaction of dialkyltin(iv) oxide with diphenic acid and its sodium salt in 1 1 molar ratio (Figure 9). Structure of these compounds was confirmed by IR, H, and 13C... 

It is also worth mentioning here that two compounds containing a Zn Sn coordinate bond have been reported. The first of these is the sole example of a dialkyltin species (see Tin Organometallic Chemistry) stabilized by coordination to zinc-/3-diketonate. It was obtained by reaction of bis[3-dimethylamino)propyl]zinc with bis(dibenzoylmethanato)tin (equation 37) and its molecular structure shows a Zn Sn bond length of 2.634 A. The second compound is... 

A number of tin hydrides have been shown to deh ogenate a-halocarbonyl compounds. Species which have been used include trialkyltin hydrides (RaSnH) and dialkyltin hydrides (R2SnH2>. Dehalogenation of a-bromo ketones can be carried out under very mild conditions (-78 C, 10 min) by a mixture of SnCh and DIBAL-H in the presence of TMEDA. The reaction probably involves SnHz as an intermediate. It has been reported that reduction of (29) by NaBH4 affords (30), except in the presence of a trace of Pb(OAc)2, Ni(OAc)2 or Hg(OAc)2, in which case the a-bromine is removed selectively to afford (31). The latter reductions may involve intermediate metal hydrides. 

The polycondensation of BHET to PET proceeds in the melt at temperatures of 270-305 °C, under vacuum (< 1 mbar absolute pressure) and in the presence of Lewis acid metal compounds, such as titanium alkoxides, dialkyltin oxide, gallium oxide, germanium oxide, thallium oxide, lanthanide salts, and most commonly, antimony oxide [1,2, 22-26]. Under polymerization reaction conditions, these catalysts are generally converted to their alkoxides with ethylene glycol. Typical of such alkoxides is antimony(III) glycolate, the active catalyst for the majority of the world s PET production [27] (cf. Structure 1). 

Polyurethane hydrogels are prepared by reaction of a polyisocyanate with polyethyleneglycol. These hydrogels can swell with water and are used in medical applications, such as wound dressings. Although dialkyltin catalysts are claimed in this application, the use of organotin compounds in medical applications with potential contact with blood is questionable, and they are probably not the safest catalysts for this application. 

High molecular weight polyesters can be obtained only with special techniques because of the difficulty of obtaining complete water removal without loss of monomers. The reaction is self-catalyzed by carboxyl groups and can be catalyzed by other acids, for example, -toluenesulfonic acid and by compounds such as titanium alkoxides, dialkyltin oxides, and antimony pentafluoride. 

In complexes with antibiotics [amoxicillin, ampicillin, methiciUin, penicilUnG, cephalexin and ciprofloxacin (Figure 12.16, a-c)], polymeric compounds may be originated by direct reaction between dialkyltin(IV) chlorides and antibiotic sodium salt, or by direct reaction between trialkyltin(IV) hydroxides and free antibiotic acid. Other combinations (diorganotin oxide/free acid ligand triorganotin(IV) chloride/antibiotic salt) produce monomeric species. 

If mixed tin stabilisers are believed to be present, for example, a thio-compound and a dialkyltin dialkylcarboxylate, it is advantageons to acidify the acetone filtrate after removal of the dialkyltin oxides with hydrochloric acid, evaporate most of the acetone on a water-bath under an air-jet, cool and extract by shaking with diethyl ether. The ether extract then contains hemiesters, acids, and so on, liberated from the other types of tin stabilisers originally present and can be examined further. Although reaction products produced by... 

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