Molecular Structures of the Silicon Pyridine-2-, and Their Intra- and Intermolecular Ligand Exchange in Solution

• Published in: Crystals (Basel) 2022-07, Vol.12 (8)
• Main Authors: Seidel, Anne, Weigel, Mareike, Ehrlich, Lisa, Gericke, Robert, Brendler, Erica, Wagler, Jörg
• Format: Article
• Language: English
• Subjects: Diffraction; Pyridine; Silicon; X-rays
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst12081054

A series of pyridine-2-olates (pyO) and pyridine-2-thiolates (pyS) of silicon was studied in solid state and in solution. The crystal structures of Me[sub.3]Si(pyO) (1a), Me[sub.3]Si(pyS) (1b), Me[sub.2]Si(pyO)[sub.2] (2a), Me[sub.2]Si(pyS)[sub.2] (2b), Ph[sub.2]Si(pyO)[sub.2] (3a) and Ph[sub.2]Si(pyS)[sub.2] (3b) were determined by X-ray diffraction. For that purpose, crystals of the (at room temperature) liquid compounds 1a and 1b were grown in a capillary on the diffractometer. Compounds 1a, 1b, 2a, 2b and 3a feature tetracoordinate silicon atoms in the solid state, whereas 3b gave rise to a series of four crystal structures in which the Si atoms of this compound are hexacoordinate. Two isomers (3b1 with all-cis arrangement of the C[sub.2]N[sub.2]S[sub.2] donor atoms in P1¯, and 3b2 with trans S-Si-S axis in P2[sub.1]/n) formed individual crystal batches, which allowed for their individual [sup.29]Si NMR spectroscopic study in the solid state (the determination of their chemical shift anisotropy tensors). Furthermore, the structures of a less stable modification of 3b2 (in C2/c) as well as a toluene solvate 3b2 (toluene) (in P1¯) were determined. In CDCl[sub.3], the equimolar solutions of the corresponding pairs of pyO and pyS compounds (2a/2b and 3a/3b) showed substituent scrambling with the formation of the products Me[sub.2]Si(pyO)(pyS) (2c) and Ph[sub.2]Si(pyO)(pyS) (3c), respectively, as minor components in the respective substituent exchange equilibrium.