Air Stable Iron(II) PNP Pincer Complexes as Efficient Catalysts for the Selective Alkylation of Amines with Alcohols

Abstract

As eries of well-defined iron(II)c omplexes of the types[ Fe(PNP)Br 2 ]a nd [Fe(PNP)(CO)Br 2 ] with PNP pincerl igands based on triazine andp yridine backbones were prepared and fully characterized. Thesec omplexes were tested as catalysts for the alkylation of amines by alcohols.T he high-spin complexes [Fe(PNP)Br 2 ]a re catalytically inactive. Thel ow-spin complexes [Fe(PNP)(CO)Br 2 ]b earing ac arbonyl co-ligand efficiently ands electively convert primary alcohols and aromatica nd benzylic amines selectively into mono-N-alkylateda mines in good to excellent isolated yields.Amechanisticp roposal is given. Scheme 2. Proposal for the formationo fc atalyst B (R = i-Pr). Scheme 3. Te ntative catalytic cycle with B as catalyst (R = i-Pr).

Iron‐Catalyzed Alkylation of Nitriles with Alcohols

“…The dehydrogenation and hydrogenation abilities of these complexes render them possible candidates for hydrogen‐borrowing catalysts. However, iron complexes, and particularly the pincer variants, have rarely been used as catalysts in hydrogen‐borrowing reactions. With these observations in mind, we examined Fe‐PNP complexes for the alkylation of nitriles with alcohols, a reaction requiring both dehydrogenation and hydrogenation abilities of the catalyst.…”

Retracted: Catalytic activity of Fe(II) and Cu(II) PNP pincer complexes for Suzuki coupling reaction

“…Iron(II) complexes bearing tridentate PNP pincer ligands were employed as catalysts for the selective formation of 3‐hydroxyacrylates from aromatic aldehydes and ethyldiazoacetate . Iron(II) complexes of the types [Fe(PNP)Br 2 ] and [Fe(PNP)(CO)Br 2 ] with PNP pincer ligands based on triazine and pyridine backbones were tested as catalysts for the alkylation of amines by alcohols . Fe(II) complexes stabilized by a PNP ligand based on the 2,6‐diaminopyridine scaffold were reported to efficiently couple the alcohols and amines .…”

“…[36] Iron(II) complexes of the types [Fe(PNP)Br 2 ] and [Fe(PNP)(CO)Br 2 ] with PNP pincer ligands based on triazine and pyridine backbones were tested as catalysts for the alkylation of amines by alcohols. [37] Fe(II) complexes stabilized by a PNP ligand based on the 2,6-diaminopyridine scaffold were reported to efficiently couple the alcohols and amines. [38] An air-stable, thermally robust, and well-defined Cu(I) PNP pincer complex based on 2,6-diaminopyridine which actively catalyzed the crosscouplings of a range of aryl and heteroaryl halides with different organomagnesium reagents, alkynes, and arylamines giving excellent to good isolated yields was also reported by the same group.…”

Novel N‐Alkylbenzimidazole‐Ruthenium (II) complexes: Synthesis and catalytic activity of N‐alkylating reaction under solvent‐free medium

“…After, this fascinating transformation was independently described by Grigg and Watanabe using rhodiumand ruthenium-based catalysts, respectively, [24,25] a great number of Ru, Ir, Pd, Co, Cu, Fe, and Mn complexes were synthesized and used as the catalyst for alkylation of amines with alcohols. [26][27][28][29][30][31][32][33] The goal of the new catalyst design is more selective and efficient catalyst and milder condition such as low temperature, low amount of catalysts, low amount of base, solvent free. Among the metal complexes, inexpensive ruthenium complexes show excellent activity for N-alkylation of amines with alcohols.…”