The
negative oxidation state of gold (Au) has drawn a great attention
due to its unusual valence state that induces exotic properties in
its compounds, including ferroelectricity and electronic polarization.
Although monatomic anionic gold (Au<sup>–</sup>) has been reported,
a higher negative oxidation state of Au has not been observed yet.
Here we propose that high pressure becomes a controllable method for
preparing high negative oxidation state of Au through its reaction
with lithium. First-principles calculations in combination with swarm
structural searches disclosed chemical reactions between Au and Li
at high pressure, where stable Li-rich aurides with unexpected stoichiometries
(e.g., Li<sub>4</sub>Au and Li<sub>5</sub>Au) emerge. These compounds
exhibit intriguing structural features like Au-centered polyhedrons
and a graphene-like Li sublattice, where each Au gains more than one
electron donated by Li and acts as a 6p-element. The high negative
oxidation state of Au has also been achieved through its reactions
with other alkali metals (e.g., Cs) under pressures. Our work provides
a useful strategy for achieving diverse Au anions