Organic heterobimetallic complexes of the alkaline earth metals (Ae = Ca, Sr, Ba) with tetrahedral metallate anions of three-valent metals (M = B, Al, Ga, and V)

Heterobimetallic compounds with complex cations of the very electropositive alkaline earth metals (Ae) and organic tetrahedral anions of trivalent elements (M) form solvent-separated ions. Depending on the metals, they can be prepared by addition of carbanions or amides to MR(3), via reduction of VMes(4) with the alkaline earth metals and by transmetallation of VMes(3). For comparison reasons selected alkali metal derivatives are also included in this study. Average structural parameters of the boranates [Ca(thf)(6)][BPh(4)](2) (1) and [CaI(thf)(5)][BPh(4)] (2), the alanates [Li(thf)(2)(tmeda)][AlPh(3)(tmp)] (3), [(thf)(2)K(N-carbazolyl)(2)AlMes(2)] (4), and [Sr(thf)(7)][AlPh(4)](2) (5), of the gallate [Ca(dme)(4)][GaEt(3)(N-carbazolyl)](2) (6), and of the vanadates [Li(thf)(4)][VMes(4)] (7), [CaI(thf)(5)][VMes(4)] (8), [Ca(thf)(6)][VMes(4)](2) (9), and [Sr(thf)(6)][VMes(4)](2) (10), are discussed. All these complexes contain complex cations of the type [(L)(n)M](+), and tetrahedral anions of the type [ER(4)](-). Only 4 crystallizes as a contact ion pair because the soft K(+) cation shows no preference for hard bases such as ethers or for soft arene pi-systems.