The metal carbonyl clusters have been recognized as one of the most successful organometallic complexes with extensive catalytic applications. In this paper, we carried out a DFT study of the stability, electronic structure and thermodynamic properties of the intermediates [M3(CO)11] and [M3(CO)10] in the synthesis of [M3(2,3-bpp)(CO)10] (M=Ru and Os). CO binding energy analysis revealed that [M3(CO)10(μ-CO)], [Ru3(CO)8(μ-CO)2] and [Os3(CO)6(μ3-CO)2(μ-CO)2] are the most stables compounds due to the presence of bridge carbonyls which favor a covalent interaction. Sigma donation from the carbonyl to metal d orbital is the most significant contribution. Moreover, spectroscopic and computational studies indicated that [Ru3(2,3-bpp)(CO)10] is in good agreement with the analogues osmium complex. Regarding the pathway associated to the formation of [M3(2,3-bpp)(CO)10] we have found that the determinant step is the dissociation of a second CO axial into [M3(CO)10(μ-CO)]. Thus, unsaturated metal carbonyl intermediates exert a thermodynamic and kinetically control as consequence of the orbital reorganization.