Heterometallic carboxylate complexes are of paramount interest in pure and applied coordination chemistry. Despite that plurality of such type compounds have been published to date, synthetic aspects of their chemistry often remain in the shadow of intriguing physical properties manifesting by these species. Present review summarizes reliable data on direct synthesis of low nuclearity molecular compounds as well as coordination polymers on their base with carboxylate-bridged {M₂Mg} (M = Co²⁺, Ni²⁺, Cd²⁺), {M₂Li₂} (M = Co²⁺, Ni²⁺, Zn²⁺, VO²⁺), {M₂Ln₂} and {M₂Ln} (M = Cu²⁺, Zn²⁺, Co²⁺) metal cores. Structural features and stabilization factors are considered and principal outcomes are confirmed by quantum-chemical calculations. Particular attention is paid to consideration of ligand-exchange reactions that allow controllable modification of heterometallic metal core under mild conditions giving diverse molecular complexes with modified ligand environment or Metal-Organic Frameworks with permanent porosity.