Complexes of Methyltin Halides

The data reported in the literature on molecular complexes of trimethyl-tin halides demonstrate that these have a 1 1 composition with mono- 

It is also noteworthy that there arc many complexes whose isolation in the individual state is impossible. However, methods such as NQR or Mossbaucr spectroscopy allow one to study the complexes in frozen solutions. 

As for the spectral parameters [e.g., v(Sn—X) or J(lH—C—119Sn)] of methyltin halides dissolved in electron-donor solvents, they should be tested in each individual case to see whether they correspond to nondis-sociated complexes or to an equilibrium between the complex and the uncomplexed halide. 

Together with stereochemical problems, the ways in which the Sn—C and Sn—X bonds are affected on going from a methyltin halide to its molecular complex are of interest. Such information is quite helpful in interpreting the reactivities of methyltin halides in various solvents (110, 117). 

More than twenty molecular complexes of methyltin halides with electron-donor solvents (111) were reported in 1973 and their structures were studied by NQR (112), Mossbaucr (118), and NMR (116) techniques. These and other data will be discussed under individual types of the complexes. 

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The same group198 characterized the complexes of methyltin halides with dibenzyl, diethyl and methyl benzyl sulphoxides. R3SnCl forms complexes with one and R2SnCl2 with two donor molecules, and trigonal bipyramidal and octahedral structures, respectively, were suggested for these complexes as shown in Scheme 16. 

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). 

The Basic Types of Structures for Molecular Complexes of Methyltin Halides... 

The molecular complexes of methyltin halides with various electron-donating solvents have been given a great deal of attention by a number of workers. 

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. 

The Sn—C bond frequencies are rather less sensitive to electronic effects in methyltin halides and depend weakly on either the number or the nature of the halogens. The increases associated with complex formation are also insignificant. Vibrational spectroscopy is a good tool not only for studying the spatial arrangement and ionicities of Sn—X bonds but also for measur-... 

The data obtained, when analyzed as a whole, show that Me3SnBr-DMSO may be the strongest complex among molecular complexes of tri-methyltin halides with monodentate ligands. 

Mctallocarboranes, Ten Years of, 14, 145 Methyltin Halides and Their Molecular Complexes, 14, 63 Nitrogen Groups in Metal Carbonyl and Related Complexes, 10, 115 Nitrosyls, 7, 211... 

Relaxation by the spin-rotation mechanism can lead to 5/Ti correlations, as observed in Sn resonance for methyltin halides, since is directly related to the spin-rotation tensor, and the spin-rotation relaxation rate to its square. With the use of higher magnetic fields, shielding anisotropy relaxation is more often observed AajTi, T2 relationships are reported for Pt(IV) complexes with Pt anisotropies of 10 ppm. ... 

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