Into the Role of Unsaturated Trinuclear Metal Carbonyls in the Formation of [M3(2,3-bpp)(CO)10] with M=Ru, Os: A DFT Stability Analysis and Electronic Structure

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 [M-3(CO)(11)] and [M-3(CO)(10)] in the synthesis of [M-3(2,3-bpp)(CO)(10)] (M=Ru and Os). CO binding energy analysis revealed that [M-3(CO)(10)(mu-CO)], [Ru-3(CO)(8)(mu-CO)(2)] and [Os-3(CO)(6)(mu(3)-CO)(2)(mu-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 [Ru-3(2,3-bpp)(CO)(10)] is in good agreement with the analogues osmium complex. Regarding the pathway associated to the formation of [M-3(2,3-bpp)(CO)(10)] we have found that the determinant step is the dissociation of a second CO axial into [M-3(CO)(10)(mu-CO)]. Thus, unsaturated metal carbonyl intermediates exert a thermodynamic and kinetically control as consequence of the orbital reorganization.

Automated summary

In this study, the stability, electronic structure, and thermodynamic properties of intermediates [M-3(CO)(11)] and [M-3(CO)(10)] in the synthesis of [M-3(2,3-bpp)(CO)(10)] (M=Ru and Os) were investigated using DFT. The analysis of CO binding energy revealed that compounds [M-3(CO)(10)(mu-CO)], [Ru-3(CO)(8)(mu-CO)(2)], and [Os-3(CO)(6)(mu(3)-CO)(2)(mu-CO)(2)] are the most stable due to the presence of bridge carbonyls, favoring a covalent interaction. The most significant contribution was the sigma donation from the carbonyl to the metal d orbital. Spectroscopic and computational studies indicated good agreement between [Ru-3(2,3-bpp)(CO)(10)] and the osmium analogue. The determinant step in the formation of [M-3(2,3-bpp)(CO)(10)] was found to be the dissociation of a second axial CO into [M-3(CO)(10)(mu-CO)], and the unsaturated metal carbonyl intermediates exerted thermodynamic and kinetic control due to orbital reorganization.