  We study the exchange interactions and resulting magnetic phases in the
honeycomb cobaltates. For a broad range of trigonal crystal fields acting on
Co2+ ions, the low-energy pseudospin-1/2 Hamiltonian is dominated by
bond-dependent Ising couplings that constitute the Kitaev model. The non-Kitaev
terms nearly vanish at small values of trigonal field \Delta, resulting in spin
liquid ground state. Considering Na3Co2SbO6 as an example, we find that this
compound is proximate to a Kitaev spin liquid phase, and can be driven into it
by slightly reducing \Delta by \sim 20 meV, e.g., via strain or pressure
control. We argue that due to the more localized nature of the magnetic
electrons in 3d compounds, cobaltates offer the most promising search area for
Kitaev model physics.
