Dissolved cobalt(0) complexes of the type [L3L'Co] (L = phosphanes, e.g. PMe3, L' = olefins, e.g. C2H4) are reversibly reduced by alkali metals A (A = Li, K, Rb, Cs)
n[L3L'Co] + A ⇋ A[L3L'Co]
and hence can be used as A-carriers. These carrier complexes A[L3L'Co]n are even soluble in apolar solvents like pentane.
Action of [L3L'Co] plus A in pentane solution on graphite yields binary intercalation compounds ACn. By contrast, conventional ambient temperature A-transfer reagents (e.g. solutions of A in naphthalene-ether or in NH3) require strongly polar solvents and yield ternary intercalation compounds A(solv)yCn.
The “reducing power” of the alkali cobaltates is close to that of free A: alkali-rich phases like 1st stage KC8 or LiC6 or highly doped polyacetylenes (e.g. K(CH)5) are readily prepared. If intercalation of solvated species is unlikely, the A-transfer reactions may also be performed in polar solvents like ethers.