Synthesis and Reactivity of Alkali Metal Hydrido-Magnesiate Complexes which Exhibit Group 1 Metal Counter-Cation Specific Stability

Abstract

Reactions of the series of alkali metal amides M(HMDS) (M = Li-Cs; HMDS = [N(SiMe₃)₂]^-) with the neutral magnesium(II) hydride compound [Mg(BDI^Dipp)(μ-H)]₂ (BDI^Dipp = [CH{C(Me)NDipp}₂], Dipp = 2,6-ⁱPr₂-C₆H₃) have been carried out. When M = Li or Na, the reactions yielded Mg(BDI^Dipp)(HMDS) and MH as the primary products. In the sodium amide reaction, [Na₂(HMDS)][{Mg(BDI^Dipp)}₂(H)₃] was obtained as a low-yield by-product. When M = K-Cs, the reactions gave the group 1 metal hydrido-magnesiates, M₂[Mg(BDI^Dipp)(HMDS)(H)]₂·(benzene)_n (n = 0 or 1), the thermal stability of which increases with the increasing molecular weight of the alkali metal involved. Reactions of Cs₂[Mg(BDI^Dipp)(HMDS)(H)]₂·(benzene) with 18-crown-6 and CO gave the first monomeric alkali metal hydrido-magnesiate [Cs(18-crown-6)][Mg(BDI^Dipp)(HMDS)(H)] and the ethenediolate complex Cs₂[{Mg(BDI^Dipp)(HMDS)}₂(μ-C₂H₂O₂)], respectively. The new synthetic route to alkali metal hydrido-magnesiates described herein may facilitate further reactivity studies of this rare compound class.