Tetraorganotin compounds

Physica.1 Properties. Physical properties of typical tetraorganotin compounds are shown in Table 3. AH tetraorganotin compounds are insoluble in water but are soluble in many organic solvents. 

Table 3. Physical Properties of Typical Tetraorganotin Compounds ...

The Wurtz reaction, which reties on in situ formation of an active organosodium species, is also usefiil for preparing tetraorganotin compounds and is practiced commercially. Yields are usually only fair and a variety of by-products, including ditins, also form ... 

Uses. The main use for tetraorganotin compounds is as (usually captive) intermediates for the tri-, di-, and monoorganotins. Although there have been reports in the patent Hterature of the use of tetraorganotins as components of Ziegler-Natta-type catalysts for the polymeri2ation of olefins, there is no evidence that such catalysts ate used commercially. 

Kumar Das et al. obtained a unique hexacoordinated tetraorganotin compound, bis C,N-[3-(2-pyridyl)-2-thienyl] diphenyltin(IV). The crystal... 

The tetraorganotin compounds, R4Sn, show no tendency to increase their coordination number, owing to their weak, Lewis acidity conferred by the four electron-releasing alkyl groups. It has, however, been claimed (353) that trimethyl(trifluoromethyl)tin forms a 1 1 adduct with hexamethylphosphoric triamide, and that this may be isolated in the solid state. 

In 1935, Naumov and Manulkin 7) tried without success to isolate (—)-methyl-ethylpropyltin iodide, (—)-(/). In fact, triorganotin halides are generally configurationally unstable, as shown in 1968 by Peddle and Redl8), whereas tetraorganotin compounds appeared to be configurationally stable within the NMR time-scale (see below). 

Compound (+ )-(53) has been made from one of the diastereomers of the (—)-menthyl ester of 3-(p-anisylmethyl-l-naphthylstannyl)propionic acid, (54) ([a]p°° — 24) which could be obtained from the mixture of diastereomers because it is much less soluble in -pentane at low temperature than the other one. Their separation could be followed by NMR, both diastereomers differing by the position of their methoxy signal. The pure less soluble diastereomer (54) reacts with methylmagnesium iodide to give a tetraorganotin compound containing only one chiral center, the asymmetric tin atom 36> 87>. 

Table 6. Room temperature partial chromatographic resolution of 75 mg tetraorganotin compounds on microcrystalline cellulose triacetate (column A)...

A trapping experiment of the optically active triorganotin chloride (5) with isopropylmagnesium bromide did give the expected methylneophylphenylisopropyltin (9) in a 20% yield but unfortunately, this tetraorganotin compound, which is optically stable (see Table 1), was obtained as a racemic mixture. 

Figure 42 shows spectra of the simplest tetraorganotin compound, tetramethyltin. The upper spectrum was recorded with complete decoupling of all protons, the middle spectrum without. The result is a multiplet with 13 lines (n = 12), but if you work out the binomial coefficients for such a multiplet you will see that the outer two lines are too weak to be seen. The lower spectrum is the proton spectrum, which shows satellites due to two-bond tin-proton coupling to the tin-117 (inner lines) and tin-119 (outer lines) nuclei. 

Triorganotin Bromide. Tetraorganotin compounds were brominated with stoichiometric quantities of bromine (2 moles of bromine for each mole of tetraorganotin). Bromination was carried out after cooling the tetraorganotin compound in a dry ice-acetone bath. The contents then were slowly brought to room temperature. In most cases, the crude bromides were used as such for fluorination. 

Synthesis and Characterization. Tris(trimethylsilylpropyl)tin fluoride (PTF) and tris(trimethylsilylmethyl)tin fluoride (MTF) were synthesized according to scheme A (Figure 1) while scheme B (Figure 1) was followed in the synthesis of dibutyl-(trimethylsilylpropyl)tin fluoride (BTF). MTF has been reported in the literature (6) however, it was synthesized to compare its solution properties with the other two novel compounds. The steps involved in these syntheses were straight-forward and thus need no elaboration. In the synthesis of BTF, the unsymmetrical triorganotin fluoride, bromination of tetraorganotin compound resulted... 

Also shown in the same table are boiling points and the refractive indices of the tetraorganotin compounds, which are the precursors of MTF, PTF, and BTF. 

Although the tin atom is a poorer acceptor than in the presence of more electronegative substituents, a number of higher-coordinate tetraorganotin compounds are now established where a donor group is present in a suitable position. 

Tetraorganotin compounds, R4Sn, show weak acceptor properties and do not form solid adducts, with the possible exception of Me3SnCF3, which is reported (53) to form a 1 1 complex with hexa-methylphosphortriamide. Tetramethyltin, for example, has little or no tendency to form complexes with a wide range of solvents, (9) since the chemical shift changes are very small (Table V). 

TABLE 43. Selected structural and NMR data for tetraorganotin compounds and triorganotin hydrides containing a potential C,N- or C,P-chelating ligand... 

Me3SnFcCH2POPh2 (231)643. The tetraorganotin compounds 366 and 367 were recently prepared (equation 66)762. 

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