Electron spin resonance and kinetic studies on tin centered radicals r3sn. with bulky substituents
- 1 January 1980
- journal article
- research article
- Published by Wiley in Bulletin des Sociétés Chimiques Belges
- Vol. 89 (10) , 907-914
- https://doi.org/10.1002/bscb.19800891016
Abstract
ESR data of stannyl radicals R3Sn. with residues R of considerable bulkiness in solution are presented. With R = neophyl (PhMe2C‐CH2), (g = 2.0150) an alternating linewidth effect indicating hindered rotation around the Sn‐C bonds is found. The radical is non‐planar by 14.0° and configurationally stable. The radicals (2, 4, 6‐alkyl3Ph) Sn., alkyl = H, Me, Et, i‐Pr show singlets (g = 2.0023 ‐ 2.0078) broadened by unresolved hyperfine interactions with ring and alkyl protons, aH ≤ 0.05 mT. They are non‐planar by 15.1 – 16.1°, (i‐Pr3Ph)3Sn. being less pyramidal than Ph3Sn because of steric repulsions between the substituents, and are in recombination‐dissociation equilibria with the corresponding distannanes. The Sn‐Sn bond energies drop from 205 kj (alkyl = Me) to 36 kJ (alkyl = i‐Pr). For (Et3Ph)3Sn., the activation energy of recombination is 38 kJ/mol.Keywords
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