A Simple Manganese(I) Catalyst for the Efficient and Selective Hydrophosphination of Olefins with PH3, Primary, and Secondary Phosphanes

• Published in: Chemistry : a European journal 2024-04, Vol.30 (20), p.e202303848-n/a
• Main Authors: Wani, Aabid A., Carballo, Juan José Gamboa, Jayaprakash, Harikrishnan, Wörle, Michael, Widera, Anna, Togni, Antonio, Grützmacher, Hansjörg
• Format: Article
• Language: English
• Subjects: Aldehydes; Alkenes; Anions; Aromatic compounds; Catalysts; Catalytic activity; Catalytic studies; Cations; Esters; Hydrophosphination; Ketones; Manganese; Manganese(I) Catalyzed; Mechanistic studies; Michael addition; Nitriles; Phosphides; Phosphines; Pyridines; Reagents; Styrene
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202303848

A tridentate ligand L with a P,NH,N donor motif was synthesized in few steps from commercially available precursors. Upon reaction with [MnBr(CO)5], an octahedral 18‐electron complex [Mn(CO)3(L)]Br (1) is obtained in which L adopts a facial arrangement. After deprotonation of the NH group in the cationic complex unit, a neutral Mn(I) amido complex [Mn(CO)2(L‐H)] (2) is formed under loss of CO. Rearrangement of L‐H leads to a trigonal bipyramidal structure in which the P and N donor centers are in trans position. Further deprotonation of 2 results in a dep‐blue anionic complex fragment [Mn(CO)2(L‐2H)]− (3). DFT calculations and a QTAIM analysis show that the amido complex 2 contains a Mn‐N bond with partial double bond character and 3 an aromatic MnN2C2 ring. The anion [Mn(CO)2(L‐2H)]− reacts with Ph2PH to give a phosphido complex, which serves as phosphide transfer reagent to activated olefins. But the catalytic activity is low. However, the neutral amido complex 2 is an excellent catalyst and with loadings as low as 0.04 mol %, turn over frequencies of >40’000 h−1 can be achieved. Furthermore, secondary and primary alkyl phosphines as well as PH3 can be added in a catalytic hydrophosphination reaction to a wide range of activated olefins such as α,β‐unsaturated aldehydes, ketones, esters, and nitriles. But also, vinyl pyridine and some styrene derivatives are converted into the corresponding phosphanes. A Mn(I) amido complex with a tridentate P,N,N ligand, which is easily synthesized from commercially available chemicals, is a remarkable efficient (pre)catalyst for the hydrophosphination of alkenes using secondary and primary aryl and alkyl phosphines and even PH3 as reagents.