Tri-tert-butoxysilanethiolate complexes of manganese(II) with chelating heterocyclic bases – Structure of compounds with a MnN2O2S2 or MnN2OS2 kernel and MeOH within the coordination sphere

The reaction of labile bis(tri-tert-butoxysilanethiolato)tetra(methanol)manganese(II) [Mn{SSi(OBut)3}2(MeOH)4] (1) with chelating heterocyclic bases (bipyridine, phenanthroline and neocuproine) resulted in the formation of new heteroleptic manganese(II) tri-tert-butoxysilanethiolate complexes exhibiting remarkable stability. Elemental and spectral analyses (IR, MS, UV–Vis) suggested that in all three cases two silanethiolate ligands and a heterocyclic base are attached to the metal centre giving complexes with [Mn{SSi(OBut)3}2(N–N)] stoichiometry, where N–N = 2,2′-bipyridine (2), 1,10-phenanthroline (3) and neocuproine (4).As a result of recrystallization from methanol monocrystals of 2 and a new, unstable complex [Mn{SSi(OBut)3}2(phen)(MeOH)] (3a) were formed and their structures determined. Both complexes are monometallic. The manganese atom in 2 is hexa-coordinated and the central MnN2O2S2 kernel results from the O,S-chelating ability of the tri-tert-butoxysilanethiolate ligand. Compound 3a represents another type of complex, where the same silanethiolate ligand is bonded to manganese only through a sulfur atom, and a methanol molecule is present within the metal coordination sphere. The structure type found in 3a is characterized by a penta-coordinated Mn centre, a MnN2OS2 kernel, and the presence of three different ligands was previously unknown among manganese compounds. Compound 3a represents an extremely rare example of a metal thiolate complex, where an alcohol molecule serves as a coligand. Furthermore, it is the first ever obtained thiolate complex where N-, O- and S-donor atoms are derived from independent ligands.

Graphical abstractThree stable [Mn{SSi(OBut)3}2(N–N)] complexes have been described, where N–N = 2,2′-bipyridine, 1,10-phenanthroline and 2,9-dimethyl-1,10-phenanthroline. For the first time one of these manganese(II) thiolate complexes have been shown to bind and release a methanol molecule.Figure optionsDownload full-size imageDownload as PowerPoint slide