Here we propose an antipodal conjecture, which is based on the synthetic
scheme of alkalide [K(C222)]+K-
, to prepare
K+[K(CO)8]-. By
introducing the concept of antipodal salts of alkalides,
K+[K(CO)8]- is
defined as antipodal salt of
[K(C222)]+K-. As Group 1
elements of the Periodic Table, the alkali metal K is conventionally
considered to form chemical bonding through its 4s and 4p valence
orbitals. Our theoretical results show that the 3d orbitals of K element
in >[K(CO)8]-
participate in chemical bonding of
>[K(CO)8]-. This
makes the alkali metal K shows typical transition metal chemical
properties, which also provides the possibility for the synthesis of
K+[K(CO)8]-.
Based on the Born-Haber thermodynamic cycle, the upper-limit stable
temperature of
K+[K(CO)8]- is
estimated to be 24.426 K . Our theoretical results indicate that
antipodal salts of alkalides will be a new family of compounds with good
synthetic prospects.