DFT Study on the Mechanism of Iron-Catalyzed Diazocarbonylation

• Main Authors: Tímea R. Kégl, László Kollár, Tamás Kégl
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: Molecules
• Subjects: iron-carbonyls; diazocarbonylation; DFT
• Online Access: https://www.mdpi.com/1420-3049/25/24/5860

The mechanism of the carbonylation of diazomethane in the presence of iron–carbonyl–phosphine catalysts has been investigated by means of DFT calculations at the M06/def-TZVP//B97D3/def2-TZVP level of theory, in combination with the SMD solvation method. The reaction rate is determined by the formation of the coordinatively unsaturated doublet-state Fe(CO)₃(P) precursor followed by the diazoalkane coordination and the N₂ extrusion. The free energy of activation is predicted to be 18.5 and 28.2 kcal/mol for the PF₃ and PPh₃ containing systems, respectively. Thus, in the presence of less basic P-donor ligands with stronger <inline-formula><math display="inline"><semantics><mi>π</mi></semantics></math></inline-formula>-acceptor properties, a significant increase in the reaction rate can be expected. According to energy decomposition analysis combined with natural orbitals of chemical valence (EDA–NOCV) calculations, diazomethane in the Fe(CO)₃(phosphine)(<i>η</i>¹-CH₂N₂) adduct reveals a <inline-formula><math display="inline"><semantics><mi>π</mi></semantics></math></inline-formula>-donor–<inline-formula><math display="inline"><semantics><mi>π</mi></semantics></math></inline-formula>-acceptor type of coordination.