Correlating Mössbauer and Solution- and Solid-State ¹¹⁷Sn NMR Data with X-ray Diffraction Structural Data of Triorganotin 2-[(<i>E</i>)-2-(2-Hydroxy-5-methylphenyl)-1-diazenyl]benzoates

Abstract

A series of R3SnO2CR‘ compounds, where R = Me (1), Et (2), nBu (3), Ph (4), and cHex (5) and R‘CO2 is the carboxylate residue of 2-[(E)-2-(2-hydroxy-5-methylphenyl)-1-diazenyl]benzoic acid, has been shown by multinuclear magnetic resonance studies to be monomeric in solution. Crystallography shows that monomeric four-coordinate species are found in the solid state for 4 and 5 but polymeric structures with five-coordinate tin atoms are found for 1−3. The different behavior is ascribed to the steric demands of the tin-bound substituents. A fair correlation is found between the difference in 117Sn chemical shift between the solution and solid states and the carbonyl oxygen−tin distance of the compounds 1−5, only when the data of 4, R = Ph, are omitted. This indicates that the mesomeric effect of the phenyl group does not express its influence to the same extent in the solid and solution states, unlike the inductive effects. By contrast, a good correlation including 4 is found between the Mössbauer quadrupole splitting and the difference in 117Sn chemical shift between the solution and solid states. This shows that the nature of the organic group on the tin atom contributes to similar extents to the values of the 117Sn chemical shifts in solution and solid state, independently of the existence or not of mesomeric effects, and that the parallel behavior of QS and 117Sn chemical shifts is geometry independent.