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(BDIDipp)­(μ-H)]2 (BDIDipp = [CH­{C­(Me)­NDipp}2], Dipp = 2,6-iPr2-C6H3) have been carried out. When M = Li or Na, the reactions yielded Mg­(BDIDipp)­(HMDS) and MH as the primary products. In the sodium amide reaction, [Na2(HMDS)]­[{Mg­(BDIDipp)}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(BDIDipp)­(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(BDIDipp)­(HMDS)­(H)]2·(benzene) with 18-crown-6 and CO gave the first monomeric alkali metal hydrido-magnesiate [Cs­(18-crown-6)]­[Mg­(BDIDipp)­(HMDS)­(H)] and the ethenediolate complex Cs2[{Mg­(BDIDipp)­(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