A Homobimetallic Frustrated Lewis Pair Cobalt Catalyst for the Methanolysis of Hydrosilanes

Abstract

Abstract The bimetallic Co(I)/Co(–I) complex [Co(CO) 2 (κ 3 ‐ P , N , P ‐PN H P)][Co(CO) 4 ] ( 1 ) has shown excellent activities in the methanolysis of hydrosilanes, surpassing the related bimetallic Co(I)/Co(–I) complex [Co(CO)(PMe 2 Ph)(κ 3 ‐ P , N , P ‐PN H P)][Co(CO) 4 ] ( 2 ), the Co(II) complex [Co(Cl) 2 (κ 3 ‐ P , N , P ‐PN H P)] ( 3 ), and the Co(I) complex [Co(CO) 2 (κ 3 ‐ P , N , P ‐PN H P)]Cl ( 4 ). A comprehensive DFT study of the plausible reaction mechanisms indicates that the enhanced activity of 1 can be attributed to the presence of the [Co(CO) 4 ] – anion, which enables a frustrated Lewis pair (FLP) mechanism that provides a low energy pathway for the heterolytic splitting of the Si─H bond. The reaction mechanism entails the coordination of the hydrosilane to the Co(I) center upon decoordination of the amine functionality of the PN H P ligand, followed by heterolytic splitting of the Si─H bond with the participation of the Co(I) and Co(–I) centers. Then, the PhSiH 2 group at the Co(–I) center is transferred to the oxygen atom of a methanol molecule, which affords the [H 2 SiPh(HOMe)] + cation, regenerating the [Co(CO) 4 ] – species. [H 2 SiPh(HOMe)] + protonates the hydride at the Co(I) center, leading to the formation of H 2 and the corresponding silyl ether. Alternative reaction pathways, including alternative ionic mechanisms or NH‐assisted bifunctional mechanisms, result in higher activation energies.