Metal-organics bond dissociation energies in compounds modeling different metal-containing structures in oil have been calculated using ab initio quantum-chemical methods. It has been found that bond energies calculated by the cbs-qb3, b3lyp/dgdzvp, and b3lyp/cc-pVDZ methods for diatomic molecules are arranged in the order: E(M-O) > E(M-S), E(M-C) > E(M-N), where M = V, Ni, or Co. Vanadium oxide VO in the vanadyl porphyrin molecule has been shown to possess the strongest bond (277.4 kcal/mol). Sandwiched structures are also stable: by using the ub3lyp/6-31g(d,p) method, the decomposition energy of the sandwich (C5H5)(2)M = M + 2C(5)H(5) has been estimated and equals at 260.2 kcal/mol for M = Fe or 141.0 kcal/mol for M = Ni. The electronic structure of transition metal (M = V, Ni, Fe) complexes with pi-conjugated bonds of benzene, pyrrole, and pyridine molecules has been calculated using the ub3lyp/6-31g(d) method. The thermal stability of the complexes has been discussed in terms of bond energy.