Lewis acidity of group 14 elements toward intramolecular sulfur in ortho-aryl-thioanisoles

Abstract

The series of compounds (o-CH3SC6H4)CH2EPh3 (E = Si (1), Ge (2), Sn (3), and Pb (4)) have been synthesized and characterized by NMR spectroscopy and by single crystal X-ray diffraction. Compounds 1 and 2 are isostructural with a triclinic crystal system and P-1 space group; however, morphotropic steps occur between Ge and Sn, and Sn and Pb. While the E-S distances in 1 and 2 are 3.985 and 3.974 Å, respectively, ~100% of the sum of the respective van der Waals (vdW) radii, there is a notable distortion from tetrahedral geometry about E. Compound 3 is also triclinic with P-1 symmetry, but has two molecules in the unit cell that demonstrate a distorted tetrahedral geometry and intramolecular Sn-S distances of 3.699 and 3.829 Å, 88% and 91% of the sum of the vdW radii. Compound 4 has a Pb-S distance of 3.953 Å (91% of Σ vdW radii). The structure of the Grignard coupling product [o-(SCH3)C6H4CH2]2 is also reported.Key words: intramolecular self-assembly, silicon, germanium, tin, lead, sulfur.