Alkyltin chlorides

Alkyltin Intermedia.tes, For the most part, organotin stabilizers are produced commercially from the respective alkyl tin chloride intermediates. There are several processes used to manufacture these intermediates. The desired ratio of monoalkyl tin trichloride to dialkyltin dichloride is generally achieved by a redistribution reaction involving a second-step reaction with stannic chloride (tin(IV) chloride). By far, the most easily synthesized alkyltin chloride intermediates are the methyltin chlorides because methyl chloride reacts directiy with tin metal in the presence of a catalyst to form dimethyl tin dichloride cleanly in high yields (21). Coaddition of stannic chloride to the reactor leads directiy to almost any desired mixture of mono- and dimethyl tin chloride intermediates ... 

The other commercially important routes to alkyltin chloride intermediates utilize an indirect method having a tetraalkjitin intermediate. Tetraalkyltins are made by transmetaHation of stannic chloride with a metal alkyl where the metal is typicaHy magnesium or aluminum. Subsequent redistribution reactions with additional stannic chloride yield the desired mixture of monoalkyl tin trichloride and dialkyltin dichloride. Both / -butjitin and / -octjitin intermediates are manufactured by one of these schemes. 

Stabilizer Synthesis. The selected alkyltin chloiide intermediate reacts with either a carboxyhc acid or a mercaptan in the presence of an appropriate base, such as sodium hydroxide, to yield the alkyltin carboxylate or alkyltin mercaptide heat stabihzet. Alternatively, the alkyltin chloride can react with the base to yield the alkyltin oxide, which may or may not be isolated, for subsequent condensation with the selected carboxyhc acid or mercaptan. 

Two frequently used methods for preparing stannylthiazoles involve either direct metalation or halogen-metal exchange followed by treatment with alkyltin chloride. Dondoni et al. described a preparation of 2-, 4- and 5-trimethylstannylthiazoles in 1986 [28], For instance, 2-trimethylstannylthiazole was readily obtained by quenching 2-lithiothiazole, derived from direct metalation of thiazole, with trimethyltin chloride. 

Mercaptides are unchallenged as the ligand of choice for the other entities bonded to the tin, but carboxylates can also be used. Whereas a variety of mercaptans are used, the thioglycolic acid derivatives remain the laigest single mercaptan. Dibutyltin bis(isooctyl thioglycolate) [25168-24-5] and butyltin tris(isooctyl thioglycolate) [25852-704] are two common examples. These materials are produced by the reaction of the appropriate alkyltin chloride or oxide, and the mercaptan. 

A series of alkyltin 2-ethylhexyl mercaptopropionates is synthesised and their structure and equilibria with alkyltin 2-ethylhexyl thioglycolates and alkyltin chlorides studied by IR and 119Sn NMR. Compatibility with PVC is determined using DMA analysis of glass transition temperatures. The implications of these results on PVC stabilisation are discussed. 19 refs. 

The stabilisation effect of alkyltin thioglycolates is determined by the measurement of discoloration in a PVC formulation. The results are interpreted considering the structure of these compounds, their equilibration with alkyltin chlorides and the postulated association with chlorine atoms at the PVC primary particle surfaces. 10 refs. 

SnCU is also the principal source of alkyltin chlorides, R SnCl4 [51]. Allyltrialkyl-tin reagents react with SnCU to produce allyltrichlorotin species through an Se2 pathway (Eq. 32) [52-56], Allyltrimethylsilanes react with SnCU to produce the corresponding allyltrichlorotin (Eq. 33) [57]. Silyl enol ethers react with SnCU to give a-tri-chlorotin ketones (Eq. 34) [58]. Transmetalation or metathesis reactions of this type... 

Reactions of organotin compounds with Lewis acids by have been carried out particularly with mercury(II) salts in mechanistic studies, with SnCl4 (the Kocheshkov reaction) for the preparation of alkyltin chlorides, and with lead tetraacetate. 

Trialkylstannylalkyl)phosphonates, R3SnCHR P(0)(0R")2> can be prepared by lithia-tion of the alkylphosphonate followed by reaction with the alkyltin chloride (equation 6-20),56 or by an Arbuzov reaction between an iodomethyltin compound and a phosphite (equation 6-21).57 The activated Sn-C bond will then add to a dipolar double bond, and the phosphonate group can be reduced to CH2PH2 with lithium aluminium hydride. 

While MOssbauer spectra of a number of solid organotin compounds provided useful information on their electronic states and structures, no Mdssbauer study of matrix-isolated organotin compounds has been conducted to date. We have recently started Mdssbauer-, IR-, and UV studies on Photochemistry of alkyltin chlorides isolated in low temperature matrices and obtained preliminary results (24). 

Several studies have chosen to focus on the volatility of the alkyltin stabilizers and their by-products of PVC stabilization, alkyltin chlorides, during the calendering operation because thi.s process presents a worst case scenerio for PVC processing relatively high stabilizer levels, very high exposed surface area of hot... 

The stoichiometric reactions of alkyltin chlorides with sodium alkoxides generally yield the aUcyltin alkoxide derivatives. The method was finally extended to the preparation of Bu Sn(OR)3, in spite of earlier unsuccessful attempts ... 

It was mentioned earlier that pentafluoroethyl iodide was decomposed by magnesium in ether. Nevertheless, it has been possible to prepare several perfluoroethyltin compounds (Section V, C) by adding pentafluoroethyl iodide to a mixture of alkyltin chlorides and magnesium in tetrahydrofuran at room temperature (29). Yields of the desired product can be as high as 50%. 

---