Tetraalkyltin

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. 

The toxicity of the tetraorganotins has beenUtde studied. Available Hterature indicates that tetrabutyltin and the higher tetraalkyltins are substantially less toxic than triorganotins to mammals if taken orally (175). The high toxicity reported for tetraethyltin (LD g = 9 16 mg/kg) appears to be caused by its rapid conversion in the Hver to a triethyl tin species. 

The alkylation can also be accompHshed using tetraalkyltin compounds. Alkyldiiodostibines are formed in about 20% yield via the interaction of alkylmagnesium iodides and antimony trichloride (67). Dialkylchlorostibines are obtained in good yields by the cleavage of tetraalkyldistibines using sulfuryl chloride (91) ... 

Aldehydes and ketones are formed in reactions of arenediazonium salts with derivatives of carbonyl compounds, e.g., with oximes (Scheme 10-40, Jolad and Ra-jagopal, 1973) or with diacetyl (Scheme 10-41, Citterio et al., 1982b). In most cases yields are mediocre. Better results are obtained with CO, tetraalkyltin, and Pd(OAc)2 as catalyst (Kikukawa et al., 1987). 

The synthesis and properties of the tin-carbon bond were reviewed in reference (35). Three recent volumes of Gmelin, written by H. Schumann and I. Schumann, comprehensively cover the literature, up to the end of 1973, on tetraalkyltin compounds R Sn (36), RaSnR (37), and RtSnR, RjSnR R", and RR SnR"R " (38), and are invaluable sources of reference. 

The alkylation of tin tetrachloride with organolithium compounds, Grignard reagents, or organoaluminum compounds remains the most common route to tetraalkyltins, and thence, by the Kocheshkov disproportionation, to the various organotin halides. 

The disproportionation reactions of organotin compounds may also be regarded as alkylations by organometallic compiounds, as they involve transfer of an alkyl group from one tin atom to another. An ingenious application of this has been described in which a,ct>-distannanes are caused to disproportionate into the corresponding tetraalkyltins and 1,1-dialkyIstannacycloalkanes (65). 

Whereas bromine radicals (133) and succinimidyl radicals (134) react by the Sh2 mechanism at the tin center in tetraalkyltins, but not in alkyltin halides, alkoxyl radicals (135) and ketone triplets (136) react with alkyltin halides, but not tetraalkyltins this may reflect the conflicting, electronic demands of the radical reagents which, as electrophilic species, should be more reactive towards tetraalkyltins than alkyltin halides, but which would also tend to make use of a 5d orbital... 

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). 

For preparing the acetates, thallous acetate has been used as the reagent as an alternative to sodium acetate (182). Alternatively, the car-boxylates can be prepared directly by acidolysis of the tetraalkyltins... 

Palladium complexes also catalyze the carbonylation of halides. Aryl (see 13-13), vinylic, benzylic, and allylic halides (especially iodides) can be converted to carboxylic esters with CO, an alcohol or alkoxide, and a palladium complex. Similar reactivity was reported with vinyl triflates. Use of an amine instead of the alcohol or alkoxide leads to an amide. Reaction with an amine, AJBN, CO, and a tetraalkyltin catalyst also leads to an amide. Similar reaction with an alcohol, under Xe irradiation, leads to the ester. Benzylic and allylic halides were converted to carboxylic acids electrocatalytically, with CO and a cobalt imine complex. Vinylic halides were similarly converted with CO and nickel cyanide, under phase-transfer conditions. ... 

Thoonen S, Deelman BJ, van Koten G (2001) Platinum- and palladium-catalysed Kocheshkov redistribution of dialkyltin dichlorides or tetraalkyltins with tin tetrachloride. Chemical Communications, 18 1840-1841. 

Mamos P, Aerschot AAV, Weyns NJ, Hardewijn PA (1992) Straightforward c-8 alkylation of adenosine analogues with tetraalkyltin reagents. Tet Lett 33 2413—2416... 

The reaction of tetraalkyltin complexes with oxide surfaces was studied244,245 but no description at the molecular level has been reported. The low-temperature reactivity of tetraalkyltin (SnR4, where R=Me, Et, i-Pr, Bu) complexes toward the surface of silica was studied in detail.246 At room temperature, the complex is physisorbed. Above 100°C, the adsorbed molecules react with the OH groups and the evolution of alkanes is observed (Scheme 7.15). 

The use of organotin compounds for the preparation of organometallics and organometalloids appears to be quite versatile.9 For example, alkyltetrafluorophosphoranes have been obtained from tetraalkyltin compounds and phosphorus(Y) fluoride,10 phenylmercury(II) chloride from tetraphenyltin and mercury(II) chloride,11 and divinylbromoarsine from ( -C4H9)2-Sn(CH=CH2)2 and arsenic (III) bromide.12... 

In the context of the Marcus formulation, the lowering of the activation barrier in an inner-sphere process could arise from the reduction of the work term wp as a result of the strong interaction in the ionic products, e.g., [RitSn+ IrCU3 ] and [RitSn+TCNE ]. The electrostatic potential in such an ion pair is attractive and may cause the tetraalkyltin to achieve a quasi five-coordinate configuration in the precursor complex, reminiscent of a variety of trigonal bipyramidal structures already well-known for tin(IV) derivatives, i.e.,... 

Wong and coworkers37 studied a series of both symmetrical and unsymmetrical tetraalkyltin compounds with different alkyl substituents, focusing their attention on the effect of these on the ionization energy of the highest occupied MOs. It is useful to recall the type of molecular orbitals deriving from the triply degenerate HOMO in the symmetrical R4M (local symmetry Td) upon substitution of one or more R ... 

Tetraalkyltin compounds are prepared by treating R3A1 with Sn(OAc)4 (R = Ci ig) in THF111. 

The various tetraalkyltin compounds were then identified and quantitated by GC MS and gas chromatography-atomic absorption analyses. The results indicated that tin(II) chloride in the simulated sea water was converted into methyltin trichloride and dimethyltin dichloride. The tin(IV) chloride, on the other hand, only formed methyltin trichloride. No trace of trimethyltin chloride was found from either tin(II) or tin(IV). The maximum amount of methyltin trichloride was formed near pH = 6 and at a salinity of 28%. The rate expression for the reaction is... 

The most toxic of the organotin compounds are the trialkyltins, followed by the dialkyltins and monoalkyltins. The tetraalkyltins are metabolized to their tri-alkyltin homologs their effects are those of the trialkyltins, with severity of effects dependent on the rate of metabolic conversion, hr each major organotin group, the ethyl derivative is the most toxic. ... 

The preparation of a number of 5-(alkyl)thianthrenium perchlorates has been performed from the thianthrene cation radical with dialkylmercurials and tetraalkyltins (R4Sn) <1983JOC143>. Thianthrene as well as phenoxathiin cation radical perchlorates react with alkenes. The former add stereospecifically to cycloalkenes although the latter afforded a mixture of mono- and bis-adducts in which the configuration of the alkene was retained <2003JOC8910>. 

The first instance of SFC coupled to ICP-MS was reported by Shen et al. [127] for the speciation of tetraalkyltin compounds. Liquid C02 was used as the mobile phase and the SFC column was completely inserted through the transfer line and connected to a frit restrictor (Fig. 11). The restrictor was heated to approximately 200°C by a copper tube inserted into the ICP torch. Tetramethyltin (TMT), tetrabutyltin (TBT), tetraphenyltin (TPT), tributyltin acetate... 

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