Anionic Magnesium and Calcium Hydrides: Transforming CO into Unsaturated Disilyl Ethers

Abstract

The synthesis, characterisation and reactivity of two isostructural anionic magnesium and calcium complexes is reported. By X‐ray and neutron diffraction techniques, the anionic hydrides are shown to exist as dimers, held together by a range of interactions between the two anions and two bridging potassium cations. Unlike the vast proportion of previously reported dimeric group 2 hydrides, which have hydrides that bridge two group 2 centres, here the hydrides are shown to be “terminal”, but stabilised by interactions with the potassium cations. Both anionic hydrides were found to insert and couple CO under mild reaction conditions to give the corresponding group 2 cis‐ethenediolate complexes. These cis‐ethenediolate complexes were found to undergo salt elimination reactions with silyl chlorides, allowing access to small unsaturated disilyl ethers with a high percentage of their mass originating from the C1 source CO.

Enabling nucleophilic reactivity in molecular calcium fluoride complexes

“…The K + ions interact both with the calcium-bound fluoride and the π-systems of the flanking Dipp groups (d(K•••F) = 2.560(1) and 2.634(1) Å; d(K•••C) = 3.335(2)-3.505(2) Å). This structural motif is very similar to those observed both for the valence-isoelectronic aluminium oxide system [K( Dipp NON)Al(THF)O)] 2 reported previously by us and the calcium hydride complex [K( Dipp NON)Ca(OEt 2 )H)] 2 synthesized by Hicks and co-workers 25,26 .…”

“…1 and Supplementary Figs. 1 and 2) 26 . Complexes 1-Dipp (Ar = Dipp, where Dipp is 2,6-i Pr 2 C 6 H 3 ) and 1-Trip (Ar = Trip, where Trip is 2,4,6-i Pr 3 C 6 H 2 ) offer variation in the steric profile of the ligand scaffold and can be employed in the synthesis of CaF-containing complexes from a range of fluoride sources in organic media.…”