Examination of metal-π interactions in the coordination chemistry of heavy alkaline earth metal tetraarylborates

The use of the weakly binding tetraarylborate ligands and the careful selection of co-ligands afford novel contact ion pairs exclusively stabilized by Ae-π (Ae = calcium, strontium, and barium) interactions of the form [Ae(B{(3,5-Me2)C6H3}4)2(thf)n] (Ae = Ca, n = 0, 1; Sr, n = 0, 2), [Ba(B{(3,5-Me2)C6H3}4)2(thf)]. HN(SiMe3)2, 3, and [Ba(B{(4-tBu)C6H4}4)2]. Et2O, 4. The variety of and preference for binding geometries with choice of metal is considered using theoretical calculations.