Organotin chlorides

Ultimately, as the stabilization reactions continue, the metallic salts or soaps are depleted and the by-product metal chlorides result. These metal chlorides are potential Lewis acid catalysts and can greatiy accelerate the undesired dehydrochlorination of PVC. Both zinc chloride and cadmium chloride are particularly strong Lewis acids compared to the weakly acidic organotin chlorides and lead chlorides. This significant complication is effectively dealt with in commercial practice by the co-addition of alkaline-earth soaps or salts, such as calcium stearate or barium stearate, ie, by the use of mixed metal stabilizers. 

Excess alkylating reagent is required if the tetraorganotin is desired as the exclusive product. In commercial practice, the stoichiometry is kept at or below 4 1, since the cmde product is usually redistributed to lower organotin chlorides in a subsequent step and an ether is used as the solvent (86). The use of diethyl ether in the Grignard reaction has been generally replaced with tetrahydrofuran. 

The hydrides are usually prepared by reducing an organotin chloride, alkoxide, or oxide with lithium aliuninum hydride or with poly(methylsiloxane), [MeSiHO] . 

Organotin chlorides, R SnCl4 , are usually obtained from the Ko-cheshkov disproportionation between tetraalkyltins and tin tetrachloride, and other organotin derivatives, R SnX4 , are then prepared by substitution reactions of the chlorides. The chemistry of the chlorides is reviewed in reference (181). 

The organotin alkoxides RgSnOR and R2Sn(OR >2 can be prepared by treating the appropriate organotin chlorides with sodium alkoxides, and this procedure has been extended to the preparation of the monoal-kyltin trialkoxides, RSnCOR la (190), which serve as useful reagents for the synthesis of other monoalkyltin derivatives. Alternatively, the trialkoxides can be prepared by alcoholysis of the tris(amino) compounds RSn(NR )3 (191). 

Species Test compound End-point Concentration (mg/l) Concentration (mg organotin chloride/l) Reference... 

Using the PECs from section 6 and the above PNECs (Table 28), both based on the organotin chlorides, risk ratios (PEC/PNEC) can be derived for each of the identified uses of organotins these are summarized in Table 29. Regional PEC/PNEC ratios are given in Table 30. 

SEC-RI/UV has also been used to analyse some 26 thioorganotin compounds, organotin carboxylates and chlorides, essentially PVC stabilisers, and some of their main by-products and related compounds (thioesters and dithioesters, n-alkanes) [803]. Not all organotin chlorides were stable in the adopted analysis conditions. N, Ai -ethylene-bis-stearamide and -oleamide in common plastics (ABS, SAN, PUR, LDPE, PA6.6) can be analysed by SEC after derivatisation with trifluo-roacetic anhydride. SEC analysis of fatty alcohol ethoxy-lates (FAE), used as nonionic surfactants, has also been described [759]. 

Stannylated ferrocenes can be prepared by the reaction of a lithiated ferrocene with an organotin chloride, or of a lithiated stannylcyclopentadiene with FeCl2, for example, Scheme 10.305 The products can be described by the shorthand FcSn.. . where x and y indicate the number of stannyl substituents in each of the two rings. 

Conversion of the organotin chlorides into fluorides, bromides, or iodides is usually carried out with the sodium halide in acetone, and residual organotin compounds are often removed as the insoluble organotin fluorides. The fluorides can then be converted back into the bromides, chlorides, or iodides (and exchanges by other halides can be brought about with aqueous ammonium halides at room temperature).332 A 2 1 mixture (solid solution) of CsF and CsOH, mixed with silica gel, also provides a very convenient way of removing organotin halide byproducts from solution.333... 

Lithiumalkyls (R = Me, Bu, Bu ) as well as lithium diisopropylamide (R = NPr)) add readily to the P=C bond of 2,5-dimethyl-l,2,3-diazaphosphole (66) <84PS(21)97,87JOM(319)49). With methyl iodide and organotin chlorides the adduct (67) yields 4-substituted dihydro-1,2,3-diazaphospholes (68). Only in the case of reaction of methyllithium (R = Me) is lithiation at C-4 observed as a minor side reaction (Scheme 23). 

Industrially, however, organosilicon and organotin chlorides axe usually obtained by the direct Rochow process (Section 3.5.2) ... 

These redistribution reactions between metal-tin complexes not only provide extremely useful transition-metal-substituted organotin chlorides, but also demonstrate the chemical robustness of the M—Sn bonds. For example, whereas the W—Sn bond in [(CO)5WSnPh3] resists attack by dry HC1, the silicon and germanium analogs are cleaved to [C1W(C0)5] 49. 

In order to prepare non-styrenic polymer-supported organotin chlorides, which are expected to show physical properties such as mechanical strength, polarity and porosity different from those of polystyrene-based supports, Deleuze and coworkers copolymerised dibutyl[3-(allyloxy)propyl]tin chloride with N-phenylmaleimide (PMI) and l,l/-(methylene-4,l-phenylene)bismaleimide (MPBMI) to prepare the polymers 88a and 88b180. 

Hunter and coworkers started from the polymer-supported organotin chloride 95, which was reacted with aryllithium compounds to give precursors for radioiodinated pharmaceuticals192,195,196,198. 

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