Synthesis and structure of bis(thiomethyl)magnesium compounds [Mg(CH2SR)2(thf)3] (R = Me, Ph) - the first dimethylmagnesium compounds functionalized by a Lewis-basic heteroatom

Abstract

Hg(CH2SR)2, (R = Me (1), R = Ph (2)), prepared by reaction of HgCl2 with [Li2(CH2SR)2(tmeda)2], reacts with magnesium activated by mercury in boiling THF to give [Mg(CH2SR)2(thf)3] (R = Me (3), R = Ph (4)). 3 readily splitts off THF in vacuo to give the solvate free complex [Mg(CH2SMe)2] (3′). The complexes 3′ and 4 are fully characterized by microanalysis and NMR spectroscopy (1H, 13C).The X-ray structure analyses of 3 and 4 reveal mononuclear compounds with two symmetry independent molecules in the unit cell of 3. In both complexes the coordination of Mg is trigonal–bipyramidal. The two apical positions are occupied by THF and the three equatorial positions by one THF and the two thiomethyl ligands. The C–Mg–C angles are slightly greater (123.9(1)–131.0(2)°) than the ideal angle for equatorial atoms in a trigonal–bipyramidal coordination. In neither case, the sulfur atoms are involved in the coordination of Mg.