Structures of Methyltin Halides

Methyltin halides dissolved in solvents of type (i) do not enter into a noticeable donor-acceptor interaction with the solvent the tin coordination number is, therefore, unaffected. At the same time, conductivity techniques (78, 79, 140, 141, 47, 24) show that methyltin halides do not ionize in solvents such as nitromethane and nitrobenzene whose dielectric permeabilities are high (35.9 and 34.8, respectively). In this section the halide structures are discussed only in solvents of type (i). When they are dissolved in solvents of type (ii), the halides enter into complex formation these systems are dealt with under complexation of methyltin halides (see Section IV). 

Organotin cations formed through dissolving the halides in solvents of type (iii) are not discussed in this review. Their recent study has been rather limited, but they have been reviewed by Tobias (142). 

In the gas phase, no structure is known for Me3SnF. In the solid state, IR spectroscopy suggested (100, 80) a structure of the Mc3Sn+F type. X-Ray studies (26,152) demonstrate, however, that orthorhombic Me3SnF crystals have a covalent structure in which fluorine atoms alternate with 

The compound is insoluble in inert organic solvents, hence no structure in solution has been obtained. As for the PMR parameters found in methanol solution (87), the peculiarities of methanol (see above) suggest that the parameters [5OH), 0.45 ppm ./()H—C—U9Sn), 69.0 Hz] bear no relation to the structure of Me3SnF. 

Electron diffraction showed (131) that in the gas phase the compounds 

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The application of NMR to a study of the structure and complexation of tin compounds was reported by us at the 11th European Conference on Molecular Spectroscopy (114)- In the present review we would like to emphasize that a study of electronic and spatial structures of methyltin halides requires, in the first place, a study of spin-spin coupling between noSn and H and 13C in methyl groups. 

Thus, the methods discussed in the foregoing allow all the necessary information on the structures of methyltin halides in the gas phase (electron diffraction), in the crystal state (X-ray techniques, NQR, Mossbauer spectroscopy, IR spectroscopy), and in solution (NMR and IR methods) to be obtained. 

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