B. Majee

Studies on organotin compounds using the del re method : V. The chemical reactivity of organotin compounds

Abstract A simple reactivity index has been developed in terms of the Del Re approximations. The relative case of halodemetallation of organotin compounds in polar and non-polar solvents has been successfully explained by application of this reactivity index, it being shown that the relative rates of cleavage of the RSn bond in Me 3 SnR, Et 3 SnR and R 4 Sn compounds can be correlated with the appropriate reactivity index.

Action of metal halides on tetra-, penta- and hexacoordinated organotin compounds : I. The rections of mercuric halides with bis(triphenyltin) oxide, and some related reactions

Abstract Mercuric halides have been shown to reach readily at room temperature with bis(triphenyltin) oxide to produce phenylmercury halides, triphenyltin halide and polymeric diphenyltin oxide, together with small amounts of tetraphenyltin. The action of mercuric chloride on the sodium salt of triphenyltin hydroxide has also been studied, and has provided evidence for the instability of compounds containing SnOHg-system. Mercuric oxide has been show to react with triphenyltin chloride in boiling benzene to give phenylmercuric chloride and polymeric diphenyltin oxide. Possible mechanisms are suggested for the reactions observed.

Studies on organotin compounds using the Del Re method III. Variations in tin-chlorine, tin-carbon and tin-hydrogen stretching frequencies and tin-chlorine bond distance in organotin compounds

Abstract The concept of bond order has been extended to Del Re calculations, and the bond orders of tin-chlorine and tin-carbon bonds in Me 4- n SnCl n ( n = 1 to 4) type compounds have been calculated. The tin-chlorine bond order increases progressively from 0.922 in Me 3 SnCl to 0.977 in SnCl 4 , and correlates satisfactorily with the experimental tin-chlorine bond distances. The tin-carbon bond order, on the other hand, remains almost constant, in agreement with the constancy of tin-carbon bond distance in the series. The average tin-chlorine, tin-carbon and tin-hydrogen stretching frequencies in similar compounds vary linearly with the calculated bond polarities indicating variation in bond polarity to be the dominating factor. The unusually low values of the tin-carbon stretching frequency for the tin-vinyl bond compared to the tin-methyl bond in Me 3 ViSn and Et 2 Vi 2 Sn can also be explained in terms of larger polarity of the tin-vinyl bond in these compounds.

Studies on organotin compounds using the remethod II. Dipole moments of organotin compounds and variation in the tinchlorine and tincarbon bond polarity

Abstract The electric dipole moments of 20 organotin compounds containing methyl, ethyl, tert-butyl, n-butyl, phenyl and vinyl groups have been calculated using an approximate quantum mechanical procedure. The σ-charge distributions have been calculated using the Del Re method and the π-charges by the Huckel LCAO MO method using the perturbation technique. Agreement with the experimental values is generally good. The calculated bond polarity of the tinchlorine bond decreases in the order R3SnCl ⪢ R2SnCl2 ⪢ RSnCl3 ⪢ SnCl4 in accordance with the variation in the nuclear quadrupole coupling constant of chlorine in these molecules. The tincarbon bond polarity in RnSnCl–n type compounds follow the order vinyl ⪢ phenyl ⪢ methyl ⪢ ethyl ⪢ n-butyl ⪢ tert-butyl as would be expected from the relative electro- negatives of the R groups.

Studies on orgnotin compounds using the del re method : I. Heats of atomisation of organotin compounds

Abstract A method for calculating heats of atomisation of organotin compounds by the Del Re approximation together with the HUckel procedure (where π-system is also present) has been developed. Results for thirteen compounds show an excellent correlation with the experimental heats of atomisation; deviation of the experimental values from the correlation curve is less than one percent.

Studies on organotin compounds using the del re method : IV. NMR spectra of organotin compounds

Abstract Del re calculations have been extended to correlate and interpret the NMR data in the organotin compounds. The methyl proton chemical shifts have been correlated with the partial charge on the methyl hydrogen atom. Variations in 13CH and tin-proton coupling constants have been correlated with the calculated Coulomb integral values, and the relationship has been interpreted in terms of the change in the s-character of the appropriate atomic orbital using isovalent hybridisation arguments in conjunction with the calculated theoretical quantities.

Studies on organotin compounds using the Del Re method : VIII. Mössbauer spectra or organotin compounds

Abstract A method for calculating the electron density at the nucleus of the tin atom in a tetravalent compound has been developed using the quantities available from the Del Re calculations. The calculated electron densities show a fair correlation with the experimental Mossbauer isomer shifts, and a value of +3.2 × 10 −4 is obtained for (Δ R/R ), in excellent agreement with the value +3.30 × 10 −4 obtained from an independent method using internal electron conversion measurements. By defining an assymmetry parameter, A , which is a measure of the deviation of the calculated p -electron distribution from the hypothetical spherically-symmetric distribution, in which the p -electron would be distributed equally between the three p -orbitals, the experimental quadrupole splittings have been correlated and interpreted. Factors governing the magnitude of quadrupole splitting are also discussed.

Organotin derivatives of arylazobenzoic acids : II. Absorption spectra and structure

Abstract On the basis of their electronic spectra triorganotin (arylazo)benzoates are classified into three types. The derivatives of p -(arylazo)benzoic acids have spectra almost identical with those of the carboxylic acids. The spectra do not show any marked solvent dependence. On the other hand, triorganotin o -(arylazo)benzoates show a considerable bathochromic shift of the first π-π ★ transition indicating chelation through the azo-N atom. The pentacoordinated compounds having only one chelate ring have low stability towards donor solvents, e.g., ether, methanol. DMSO and the N→Sn bond is easily broken. However, the presence of a OH or NH 2 group at the o ′-position makes the azobenzoic acids terdentate. The resulting hexacoordinated tin compounds with two annelated chelate rings have marked stability towards donor solvents as indicated by the near absence of solvent effects on the absorption spectra.

Studies on organotin compounds using the Del Re method

The application of the reactivity index Zμ is extended to tin-aryl and tin-vinyl bond cleavage reactions in trialkylaryltin and trialkylvinyltin compounds. The observed reactivity sequence is interpreted, and the relative rates of tin-aryl bond cleavage in polar solvents correlated with the appropriate reactivity index.

Studies on organotin compounds using the Del Re method : VII. Bond polarisability index and reactivity of organotin compounds

Abstract Using the Del Re method a simple reactivity index, defined as the bond polarisability index, has been derived. The observed reactivity sequence for the cleavage of the alkyl groups from the metalalkyls both in the polar and in the non-polar solvents have been interpreted, and the relative rates of these reactions correlated with this index. The relative rates of the exchange reactions between trialkylaluminium and trialkyltin hydrides have also been satisfactorily interpreted.