Iminophosphanes: Synthesis, Rhodium Complexes, and Ruthenium(II)-Catalyzed Hydration of Nitriles

Abstract

Highly stable iminophosphanes, obtained from alkylating nitriles and reaction of the resulting nitrilium ions with secondary phosphanes, were explored as tunable P-monodentate and 1,3-P,N bidentate ligands in rhodium complexes. X-ray crystal structures are reported for both κ1 and κ2 complexes with the counterion in one of them being an unusual anionic coordination polymer of silver triflate. The iminophosphane-based ruthenium(II)-catalyzed hydration of benzonitrile in 1,2-dimethoxyethane (180 °C, 3 h) and water (100 °C, 24 h) and under solvent free conditions (180 °C, 3 h) results in all cases in the selective formation of benzamide with yields of up to 96%, thereby outperforming by far the reactions in which the common 2-pyridyldiphenylphosphane is used as the 1,3-P,N ligand.

Selective Hydration of Nitriles to Corresponding Amides in Air with Rh(I)-N-Heterocyclic Complex Catalysts

“…To avoid this problem, in the last decades several remarkable catalytic systems have been developed to stop hydration at the amide stage, e.g., using enzymes as biocatalysts (nitrile hydratase, NHase) [3], nanocatalysts such as a Fe 3 O 4 magnetic nanoparticles-supported Cu-NHC complex [4], or ruthenium hydroxide nanoparticles on magnetic silica [5], silver nanoparticles [6], and other heterogeneous [7][8][9][10] or homogenous catalysts. A broad spectrum of transition metal complexes based on rhodium [11,12], ruthenium [12][13][14][15], nickel [16], osmium [17], and gold [18] were employed as catalysts, and the field has been reviewed from various aspects [19][20][21][22][23][24][25][26][27][28][29].…”

Ru (III) Schiff‐base complex anchored on nanosilica as an efficient and retrievable catalyst for hydration of nitriles

“…Both homogeneous as well as heterogeneous Ru based catalysts for the synthesis of amides from nitriles were reported. But both require the use of inert atmosphere (Ar, N 2 ) or high temperature (180 °C,160 °C, 110–120 °C,100 °C,140 °C) . It has been observed that in case of heterogeneous catalysis though the catalyst/product separation is easy and the catalyst can be recycled, yet only a few examples were reported.…”

Aqueous‐Phase Nitrile Hydration Catalyzed by an In Situ Generated Air‐Stable Ruthenium Catalyst

“…With water as a reagent, and many of the product amides having modest water solubility,n itrile hydration is well suited towardsa queous-phase catalysis. [9,[13][14][15][16][17][18][19][20][21][22] Our group has been interested in the development of water-soluble phosphine ligandsf or use in catalysis. [1,[12][13][14][15][16][17] Ru II and Ru IV complexes with nitrogen-containing phosphine ligands (for example, [RuCl 2 (h 6 -arene)(P(NMe 2 ) 3 )]) have shown significant activity for nitrile hydration.…”

“…[1,[12][13][14][15][16][17] Ru II and Ru IV complexes with nitrogen-containing phosphine ligands (for example, [RuCl 2 (h 6 -arene)(P(NMe 2 ) 3 )]) have shown significant activity for nitrile hydration. [9,[13][14][15][16][17][18][19][20][21][22] Our group has been interested in the development of water-soluble phosphine ligandsf or use in catalysis. Our work has largely focused on ruthenium complexes containing the air-stable and water-soluble 1,3,5-triaza-7-phosphaadamantane (PTA) [23][24][25] and derivatives for possible aqueous-phase catalysis.…”

“…Ruthenium complexes have been utilized as efficient and versatile catalysts for nitrile hydration to amides . Ru II and Ru IV complexes with nitrogen‐containing phosphine ligands (for example, [RuCl 2 (η 6 ‐arene)(P(NMe 2 ) 3 )]) have shown significant activity for nitrile hydration …”