Group 2 metal bis(arenecarbochalcogenoate)(crown ether) complexes: isolation and structural analysis

Abstract

A series of Group 2 metal bis(arenecarbochalcogenoato)(crown ether) complexes M(EE′CAr)₂(L)(L′)_x (M = Mg, Ca, Sr, Ba; Ar = aryl; E = S, Se; E′ = O, S; L = H₂O or THF; L′ = 15-crown-5, 18-crown-6) were synthesized and their structures were revealed by X-ray analyses. The two carbothioato ligands in Mg, Ca and Sr 15-crown-5 complexes are located on the same side of the crown ether plane, while those in Mg, Ca, Sr, and Ba 18-crown-6 compounds are on both sides of the 18-crown-6 plane (trans relative to the plane). For the Ca 15-crown-5 complex, both carbothioato ligands are connected to the central Ca ion through an oxygen atom in a monodentate manner, and the two hydrogen atoms of the coordinated water molecule are intramolecularly hydrogen-bonded with thiocarbonyl sulfur atoms. One of the two carbothioate groups in the Ca 18-crown-6 complex is connected in a bidentate manner to the central metal, while the other is connected in a monodentate manner through an oxygen atom. The two thiocarboxylato ligands in the Sr 15-crown-5 congener are connected in a bidentate fashion to the same side of the crown ether plane. The Ca and Sr compounds are the first examples of alkali earth metal carbochalcogenoate complexes in which carbochalcogenolato ligands are connected in a monodentate manner through an oxygen atom. Both chalcogenoato ligands in Ba(SOCC₆H₄Me-4)₂(18-crown-6) and Sr(SeOCC₆H₄Me-4)₂(18-crown-6) are coordinated in a bidentate manner to the central metal ion.