Ronald E. Hutton

β-substituted alkyltin halides : II. Dialkyltin dihalides: mechanistic and spectroscopic aspects☆

Abstract Hydrogen halides, tin and α,β-unsaturated carbonyl compounds react together under mild conditions to give mixtures of β-substituted alkyltin trihalides and bis(β-substituted alkyl)tin dihalides: acrylonitrile is also active. Spectroscopic data for a number of pure functionally substituted dialkyltin compounds is presented. The monoalkyltin compounds are almost certainly formed by the in-situ formation of trihalogenostannanes from hydrogen halides and tin. Several possible mechanisms are discussed for the formation of the dialkyltin compounds. The substituted monoalkyltin compounds react with tin to give the corresponding dialkyltin compounds as well as products which are believed to be relatively stable tin—tin species.

The synthesis and infrared spectra of organotin(IV) mercaptoester chlorides

Abstract We have prepared several butyltin mercaptoesters and butyltin mercaptoester chlorides of the general formula BunSn(S(CH2)1–2CO2R)mCl4−(n + m) (n = 1, m = 1–3; n = 2, m = 1–2) and we have studied, in some detail, their infrared spectra in the carbonyl region. The butyltin mercaptoester chlorides exist not as pure compounds but as mixtures in equilibrium with the respective butyltin mercaptoesters and butyltin chlorides. Our results suggest that anhydrous reactions between butyltin chlorides and isooctylthioglycolate give almost entirely butyltin isooctylthioglycolate chlorides in contrast to the findings of Herber and Stapfer [J. Organometal. Chem., 66 (1974) 425] who concluded that these reagents gave trans isomers of butyltin isooctylthioglycolates.

A possible mechanism to explain the synergistic effects exhibited by mixtures of alkyltin mercaptoesters as stabilisers for PVC

Abstract The phenomenon of synergism observed with mixtures of mono- and dialkyltin stabilisers for PVC has been recognised and exploited for many years, but remains largely unexplained. Whilst a similar effect in mixed metal (Ba/Cd or Ca/Zn) carboxylate stabilisers has been explained, mechanistic studies of the organotin systems have not appeared. Infra-red spectroscopy has now been used to study the Cl/mercaptoester exchange equilibria of alkyltin mercaptoester (isooctylthioglycollate) chlorine compounds which are undoubtedly produced when the organotin mercaptoesters act as PVC stabilisers. The exchange process is shown to be facile, even at ambient temperatures, and a regenerative mechanism, based on these observations, is proposed to explain the synergistic effect.

A study of mercaptoester/chlorine exchange equilibria exhibited by β-carboalkoxyethyltin compounds

Abstract 60 MHz proton NMR data confirms that Cl/mercaptoester exchange reactions in butyl- and β-carbobutoxyethyltin compounds occur readily in deuterochloroform at 35°C. The positions of dibutyl-, monobutyl- and mixed mono-/dibutyltin equilibria are dictated by intramolecular carbonyl to tin coordination from the mercaptoester groups. In the analogous β-carbobutoxyethyltin systems the corresponding equilibria are perturbed by the competing carbonyl to tin coordination from the β-carbobutoxyethyl groups. These results are correlated with the activity of alkyltin and β-carboalkoxyethyltin stabilisers in PVC.

Redistribution reactions of β-carboalkoxyethyltin compounds

Abstract Carboalkoxyethyltin compounds undergo redistribution reactions at faster rates than similar unsubstituted alkyltin compounds. In redistribution reactions between SnCI4and carboalkoxyethyltin compounds stable intermolecular complexes are formed. Rate enhancement is explained in terms of intra- and intermolecular coordination effects. Where strong intermolecular coordination effects are observed, specific electrophilic cleavage of the carboalkoxyethyl group can occur in preference to alkyl cleavage in mixed carboalkoxyethylalkyltin compounds. The presence of a β-ester function can catalyse both alkyl/chlorine and alkyl/alkyl′ exchange reactions.

New synthesis of β-substituted alkyltin halides via halogenostannane intermediates

β-Substituted ethyltin trihalides and bis-(β-substituted ethyl)tin dihalides can be prepared via the in situ reaction of αβ-unsaturated carbonyl compounds with active halogenostannane intermediates produced from halogen acids and tin(II) chloride or halogen acids and metallic tin, respectively.

β-Substituted alkyltin halides: III. Synthesis of trialkyltin halides and tetraalkyltins☆

Abstract (β-Carboalkoxyethyl)tin trihalides and bis(β-carboalkoxyethyl)tin dihalides react with metallic zinc to give mixtures of the corresponding tris(β-carboalkoxyethyl)tin halides and the tetra(β-carboalkoxyethyl)tins. Bis(β-carboalkoxyethyl)tin diacetates react with metallic zinc to give only the corresponding tetra(β-carboalkoxyethyl)tin compounds. The mechanisms of these reactions are discussed. Conversion of the bis(β-carboalkoxyethyl)tin dihalides into the tris(β-carboalkoxyethyl)tin halides is believed to occur by a two-step process, with the tetra(β-carboalkoxyethyl)tin compounds as intermediate products. The 270 MHz NMR spectra of the (β-carbobutoxyethyl)tin compounds are presented.