The potential energy surfaces for eight low-lying electronic states of the Ph-CO and Rh-OC complexes and of the Ir-CO and Ir-OC complexes have been studied using the complete active space multiconfiguration self-consistent field method followed by the multireference singles+doubles configuration interaction calculations which included up to 1.6 million configurations. In addition, spin-orbit effects are included through the relativistic configuration interaction method for the Ir-CO complex. It is found that the Rh(F-2) and Ir(2F) states react spontaneously with CO to form stable RhCO and IrCO molecules in which the (2) Delta ground states are 42.4 and 75.1 kcal/mol more stable than Rh(F-2)+CO((1) Sigma(+)) and Ir(F-2)+CO((1) Sigma(+)) states, respectively, in the absence of spin-orbit effects. The RhOC and IrOC complexes in the (2) Delta states were found to be less stable than Rh(F-4)+CO((1) Sigma(+)) and Ir(F-4)+CO((1) Sigma(+)), respectively. The nature of the chemical bond is discussed in terms of the wave function composition, and the electronic population analysis.