Phosphine–Imidazolyl Ligands for the Efficient Ruthenium‐Catalyzed Hydrogenation of Carboxylic Esters

Abstract

The synthesis of phosphine-imidazolyl ligands 1 and 2 in good yields is presented. In combination with [{Ru(benzene)Cl(2)}(2)], ligands 1 c and 1 e formed efficient catalyst systems for the selective hydrogenation of various carboxylic esters into their corresponding primary alcohols. Furthermore, the structures of four ruthenium complexes with ligands 1 b, 1 c, 1 d, and 1 e were determined by X-ray crystallography, which showed the formation of different coordination modes depending on the ligand structure.

Methoxyphenyl Substituted Bis(picolyl)phosphines and Phosphine Oxides

“…All spectra were measured, if not mentioned otherwise, at 25°C. The assignment of the signals in the 1 H and 13 C NMR spectra is based on 2D ( 1 H, 1 H-CO-SY45, 1 H, 13 C-HMQC and 1 H, 13 C-HMBC) experiments. For the HMBC NMR spectra a sinebell window function and a zero filling in both directions was applied resulting in a 4k × 4k matrix.…”

“…[1] By virtue of these coordination behaviours, metal complexes bearing P,N ligands display a huge variety of assorted properties, and hence, have many possible applications. [1] Transition metal complexes of picolyl-substituted organophosphines (picolyl = C 5 H 4 N-2-CH 2 -) show many different catalytic activities; these include, but are not limited to applications in: i) reductive amination, [2] ii) catalytic hydrogenation of unactivated amides, [3] and iii) catalytic oligomerization of ethylene.…”

“…Phosphine 1 was first synthesized in 1983 by Lindner and co-workers. Group VI transition metal complexes of 1 were characterized by 1 H, 13 C and 31 P NMR spectroscopy and, in the case of the literature known tris(picolyl)phosphine (2) and its new phosphine oxide derivative, single-crystal X-ray analysis was applied to structure elucidation efforts. The determination of the molecular structure of (o-methoxyphenyl)dichlorophosphine (3a) was achieved by X-ray analysis of a co-crystal consisting of 3a and its rare phosphonic anhydride derivative 8.…”

“…[7] The NiCl 2 (1) and CrCl 3 (1) complexes show catalytic activity in the oligomerization of ethylene; Fe II complexes with 1 have also been made. [9] In the Ag I and Cu I complexes of 1 with non-coordinating anions, a series of different binding modes of the ligand could be observed.…”

Ruthenium complexes of diphenylphosphino derivatives of carboxylic amides: Synthesis and characterization of bidentate P,N- and P,O-chelate ligands and their reactivity towards [RuCl2(PPh3)3]

“…(Furthermore, carboxylic amides with phosphine functionalization in α-position [4,5] or other positions of the organic backbone [6], have been studied in transition metal coordination chemistry.) In general, the P,N [7] and P,O [8] bidentate donor sets may exhibit mono-vs. bidentate ligand characteristics, and in combination with rather soft transition metal atoms the phosphorus atom represents the superior σ-donor over the N or O atom in case of monodentate binding in the transition metal coordination sphere (A, B and C in Scheme 1). This hemilabile property is supportive in many catalytic processes like oligo-and polymerization, carbonylation as well as hydro-and dehydrogenation [8][9][10][11][12].…”