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

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 C-1 source CO.

Automated summary

The synthesis, characterisation and reactivity of two isostructural anionic magnesium and calcium complexes are reported. The anionic hydrides exist as dimers held together by interactions between the two anions and bridging potassium cations. The hydrides are terminal and stabilized by interactions with the potassium cations. They can insert and couple CO under mild conditions to give the corresponding group 2 cis-ethenediolate complexes. These complexes can undergo salt elimination reactions with silyl chlorides, leading to small unsaturated disilyl ethers with a high percentage of their mass originating from CO.