Tetraorgano compounds

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. 

Data for these RaSnD species are collected in Table 7, which also includes the one example of six-coordinate R4SnD2 (14g). Note that d in Table 7 is Ph Sn bonded to OH in a similar environment to c and e is the MeSn diptych (neither is illustrated). 

5 For the analogous bromide, SnN shortens to 249.6 pm, SnBr = 266.7 pm, Sn/C parameters remain similar, CSnBr angles are reduced and CSnN angles increased V 

A tetraorganotin member, Me3Sn-l,4-cyclohexadiene-COOMe, is included with the triorganotin series summarized in Table 8 (see later). 

As H is a very similar ligand to R, the chiral f-butyl(8-dimethylaminonaphthyl)(—)men-thyltin hydride120 is included with the tetraorganics. A weak Sn... N interaction (SnN = 290.3 pm) perturbs the shape towards trigonal bipyramidal (Sn-H = 157 pm, Sn-Bu = 221.2 pm, Sn-Nt = 215.7 pm, Sn-Menthyl = 218.3 pm). 

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Because a number of these organometallic compounds are commercially available, they are convenient starting materials for the preparation of certain aliphatic and aromatic diorgano tellurium dihalides. Tetraorgano tin and lead compounds transfer only two of their four organic groups to tellurium. Experiments with dialkyl-diaryl compounds showed that only the aryl groups are transferred. 

One Te-C bond in tetraorgano tellurium compounds is easily cleaved by water2,3, hydrogen chloride4,5, halogens4,5, dichloromethane, and chloroform2 with formation of triorgano telluronium halides. 

Triorgano telluronium halides reacted with organo lithium compounds to produce tetraorgano telluriums5,6. 

V. Tetraorgano Tellurium, Alkylidene Diorgano Tellurium Compounds, and Hexaorgano Telluriums... 

Only a few tetraorgano tellurium compounds have been synthesized and characterized. Tetraaryl tellurium compounds have a higher thermal stability than tetraalkyl tellurium compounds. Tetraphenyl tellurium has a distorted trigonal bipyramidal geometry2. 

K. J. Irgolic Tetraorgano, Alkyliden Diorgano, Hexaorgano Tellurium Compounds... 

Triorgano telluronium halides reacted with organic lithium compounds to form tetraorgano tellurium compounds1 5. 

Water, hydrochloric acid, bromine, iodine, and methyl iodide heterolytically cleave one Te — C bond in tetraorgano tellurium compounds with the bonding electron pail remaining with the organic group. The products of these reactions are triorgano tellurium compounds (see p. 692). 

The diorgano tellurium dicarboxylates are white, crystalline materials that are soluble in organic solvents and stable towards atmospheric agents. Diaryl tellurium diacetates can be boiled in water without decomposition. However, bis[trifluoromethyl] tellurium bis trifluoroacetate] was reported to be moisture-sensitive. Aqueous sodium hydroxide converts diaryl tellurium dicarboxylates to diaryl tellurium oxides or dihydroxides . Thermal gravimetric analysis of diaryl tellurium dicarboxylates indicated that these compounds lose carbon dioxide at 240-260° and form the tetraaryl tellurium derivatives. The tetraorgano tellurium compounds decompose slowly to the diaryl tellurium compounds and hydrocarbons. ... 

Tetraorgano tellurium compounds are thermally decomposed to diorgano tellurium compounds and hydrocarbons . Whereas tetramethyl tellurium, tetrabutyl tellurium, and diaryl dialkyl tellurium compounds already form diorgano tellurium compounds by loss of alkyl groups at or below 20° tetraphenyl tellurium tetrakis[pentafluoro-phenyl] telluriumtetrakis[4-methylphenyl] tellurium , and bis[2,2 -biphenyldiyl] tellurium must be heated to at least 100° to effect decomposition. 

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