The structure of M(mda)2 (M = Be, Mg, Ca; mda = C3O2H3) bis-complexes was investigated by the ab initio Hartree-Fock method and by including electron correlation in terms of second order Moller-Plesset perturbation theory; for calculations we used triple-zeta valence basis sets complemented with polarization functions. Two most probable geometrical nuclear configurations (D2h and D2d) are considered for each molecule. The structure with two mutually orthogonal chelate ligands (D2d symmetry) corresponds to the potential energy surface (PES) minimum. The planar D2h configuration corresponds to the first order saddle point on PES; consequently, its relative energy determines the height of the barrier to the D2d→D2h→D2d′ intramolecular rearrangement. Correlation equations that relate the calculated values of equilibrium internuclear distances, force constants, and rearrangement barrier heights to the value of the ionic radius of the metal atom have been obtained. These correlations were employed to evaluate the molecular constants for Sr(mda)2 and Ba(mda)2. The theoretical data are compared with the available experimental literature data.