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Novel Structural Principles in Magnesium Thiolate Chemistry:  Monomers, Trimers, and the First Magnesiate Thiolate

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journal contribution
posted on 11.06.1998, 00:00 by Scott Chadwick, Ulrich Englich, Mathias O. Senge, Bruce C. Noll, Karin Ruhlandt-Senge
The synthesis and characterization of a family of magnesium thiolates [Mg(SR)2(donor)n]m (R = C6H5, C6F5, -2-NC5H4; n = 1−4; m = 1, 3) and the first magnesiate thiolate [cat]2[Mg(SC6F5)4] are described. Mg(SC6F5)2(py)3, 1 (py = pyridine), Mg(SPh)2(py)4, 2, the trimer Mg32-SPh)6(py)6, 3, the intramolecularly stabilized monomer Mg(S-2-NC5H4)2(py)2, 4, and the “ate” complex [2,6-lutidineH]2[Mg(SC6F5)4], 5, were synthesized by treating (C4H9)2Mg with HSC6F5, HSC6H5, or HS-2-NC5H4 under addition of pyridine or 2,6-dimethylpyridine. The target molecules were characterized by IR and, depending on solubility, 1H NMR and 13C NMR spectroscopy, melting point, and single-crystal X-ray crystallography. It is clearly shown that the structural chemistry, and therefore the physical properties of the magnesium thiolates, can be influenced by ligand and donor choice, as exemplified by the significant structural variations observed. Use of HSC6F5 and pyridine resulted in the formation of five-coordinate Mg(SC6F5)2(py)3·C6H5CH3, 1a, and the solvent-free Mg(SC6F5)2(py)3, 1b; while utilization of HSC6H5 and pyridine resulted in the formation of the six-coordinate species Mg(SPh)2(py)4, 2, and Mg32-SPh)6(py)6, 3. Interestingly, compounds 2 and 3 are isolated from almost identical reaction mixtures and are related by an equilibrium:  addition of large amounts of pyridine results in the formation of 2 while reduced amounts of donor allow the isolation of the novel trimer 3. The intramolecularly stabilized, distorted-octahedral complex Mg(S-2-NC5H4)2(py)2, 4, becomes available if 2-mercaptopyridine is used in conjunction with pyridine. A rare example of an anionic alkaline-earth derivative, the tetrahedrally coordinate [2,6-lutidineH]2[Mg(SC6F5)4], 5, is accessible by treating (C4H9)2Mg with 4 equiv of HSC6F5 and adding 2,6-lutidine.