We wish to make a comparative inelastic neutron scattering (INS) and ab initio study on the family of compounds: M3[Co(CN)6] (M = H, Cu, Ag). Specifically we are interested in how the varying metallophilic interactions affect phonon dynamics. Ag3[Co(CN)6] is a known colossal thermal expansion compound, which we have previously studied. Isostructural and recently reported Cu3[Co(CN)6], exhibits similar behaviour but to a lesser extent. By contrast H3[Co(CN)6] shows very little thermal expansion, with coefficients less than 10% of those for Ag3[Co(CN)6]. We believe that specific metallophilic interactions play an important role in the anharmonicity and thermal expansion mechanisms of these compounds. We expect to see less pronounced low-energy features in the measured phonon spectra of Cu3[Co(CN)6] compared to the already published Ag3[Co(CN)6], and none in H3[Co(CN)6]. This will be modelled using ab initio phonon calculations, including van der Waals' interactions, to account for weak forces and their potential effect have on the thermal expansion mechanism of these compounds.