Non-Pincer Mn(I) Organometallics for the Selective Catalytic Hydrogenation of Nitriles to Primary Amines

Abstract

We report herein selective catalytic hydrogenation of nitriles to primary amines with the use of the non-pincer Mn­(I) compound fac-[(CO)3Mn­{iPr2P­(CH2)2PiPr2}­(OTf)] (2) as a catalytic precursor (3 mol %) in the presence of KO t Bu (10 mol %) and 2-BuOH as solvent. Benchmark benzonitrile and electron-rich aromatic and aliphatic nitriles were hydrogenated under rather mild conditions (7 bar, 90 °C, 15 min) to produce the corresponding amines in excellent to very good isolated yields (83–97%, six examples). Increasing the H2 pressure and time (35 bar, 30 min) allowed for the production of (di)­amines in excellent yields (94–98%, three examples) from electron-deficient aromatic nitriles and terephthalonitrile. Notably, adiponitrile was reduced to hexamethylenediamine in 53% isolated yield. Finally, mechanistic insights were performed and suggested unsaturated Mn-hydride species performing the elementary steps during catalytic turnover.

Robust and efficient hydrogenation of carbonyl compounds catalysed by mixed donor Mn(I) pincer complexes

“…From catalysis standpoint, the formation of Mn hydride species is generally accepted as a prerequisite for entering the hydrogenation cycle 8 – 13 , 16 – 19 , 29 , 30 , 33 . Our data, on the other hand, indicated that the Mn–H formation from 4 is slow and requires the irreversible loss of one CO ligand.…”

“…These include PN aminophosphines developed by our group ( D , Fig. 1 ) 31 , diphosphines E reported by the groups of Kirchner 32 and García 33 . The most recent addition to this set was reported by Sortais and coworkers who described catalyst F (Fig.…”

A cobalt phosphide catalyst for the hydrogenation of nitriles

“…Alternatively, some improvements using homogeneous earth-abundant metal catalysts have been reported. [17][18][19][20][21][22][23][24][25][26] However, these catalysts still require high H 2 pressures and have practical drawbacks, such as difficulty of catalyst recovery and reuse, the need for synthetically complex ligands and the contamination risk of dissolved metals. Heterogeneous catalysts have numerous advantages over homogeneous catalysts, which include their high durability, facile separation from the reaction mixture and subsequent reusability.…”

Selective Manganese-Catalyzed Dimerization and Cross-Coupling of Terminal Alkynes

“…The deuterated solvents were purchased from Aldrich and dried over 3 Å molecular sieves. 2) and fac-[Mn(dippe)(CO)3(H)] 3 (3) were synthesized according to literature. Phenylacetylene-d1 (>98 % D) and 1-octyne-d1 (>98 % D) was synthesized from phenylacetylene, 1-octyne, n-BuLi and D2O.…”

“…CO ligands in Mn(I) alkyl carbonyl complexes are known to undergo migratory insertions to form highly reactive coordinatively unsaturated acyl complexes which can be trapped in the presence of strong field ligands such as CO or tertiary phosphines -a well-known textbook reaction. 1 The classic reaction is the formation of Mn(CO)5(η 1 -COCH3) from Mn(CO)5(CH3) in the presence of CO. [2][3][4] On the other hand, these acyl 16eintermediates can be utilized to activate dihydrogen, possibly also molecules featuring weakly polar E-H (E = e.g., C, Si, B) bonds. For instance, dihydrogen is able to react with transition-metal acyl complexes to afford aldehydes and metal hydride complexes.…”