Coordinatively Diverse ortho-Phosphinoaniline Complexes of Ruthenium and Isolation of a Putative Intermediate in Ketone Transfer Hydrogenation Catalysis

Abstract

Amine-functionalized mono- and diphosphines have been used to prepare a series of ruthenium complexes which exhibit a variety of coordination modes depending on the number of donors possessed by the ligands, the degree of amine methylation, the solvent system used, and the oxidation state of the metal. Reactions of the monophosphinoanilines, Ph(2)PAr or Ph(2)PAr' (Ar = o-C(6)H(4)NHMe, Ar' = o-C(6)H(4)NMe(2)), with 0.5 equiv of [RuCl(mu-Cl)(eta(6)-p-cymene)](2) in dichloromethane result in the formation of [RuCl(2)(eta(6)-p-cymene)(P-Ph(2)PAr)] or [RuCl(eta(6)-p-cymene)(P,N-Ph(2)PAr')]Cl, respectively. In refluxing methanol, [RuCl(2)(eta(6)-p-cymene)(P-Ph(2)PAr)] gradually undergoes chloride ion dissociation to afford the P,N-chelate, [RuCl(eta(6)-p-cymene)(P,N-Ph(2)PAr)]Cl. This chelate can then be deprotonated to afford the amido complex, [RuCl(eta(6)-p-cymene)(P,N-Ph(2)PAr(-))] (Ar(-) = o-C(6)H(4)NMe(-)), which is an active ketone transfer hydrogenation catalyst. Reactions of the diphosphines, Ar(2)PCH(2)PAr(2) (mapm) or Ar'(2)PCH(2)PAr'(2) (dmapm) with 0.5 equiv of [RuCl(mu-Cl)(eta(6)-p-cymene)](2) result in the formation of [RuCl(2)(P,P',N,N'-mapm)] or [RuCl(eta(6)-p-cymene)(P,P'-dmapm)]Cl, respectively, in which increased methyl substitution in the latter actually inhibits amine coordination with retention of the p-cymene fragment. Reaction of mapm with 1 equiv of [Ru(CO)(4)(eta(2)-C(2)H(4))] in dichloromethane initially produces [Ru(CO)(4)(P-mapm)] which, over a 24 h period with exposure to ambient light, is completely converted to the P,P'-chelate, [Ru(CO)(3)(P,P'-mapm)], by photodissociation of carbon monoxide. The same reaction with 2 equiv of [Ru(CO)(4)(eta(2)-C(2)H(4))] generates a mixture of [Ru(3)(CO)(10)(mu-P,P'-mapm)] and the mononuclear P,P'-chelate. The trinuclear complex can also be synthesized by direct reaction of mapm with 1 equiv of [Ru(3)(CO)(12)].

Synthesis and Structure of Trinuclear W3S4Clusters Bearing Aminophosphine Ligands and Their Reactivity toward Halides and Pseudohalides

“…6 Motivated by the good catalytic performance of group eight and nine aminophosphino complexes in hydrogenation and transfer hydrogenation reactions, we decided to design synthetic procedures aimed to functionalize the highly robust W 3 S 4 cluster core moiety with aminophosphine ligands. 1,[18][19][20][21][22][23][24][25][26] In particular, we have 5 chosen (2-aminoethyl)diphenylphosphine (edpp), bearing a NH 2 function that can serve not only as coordination group but also as hydrogen donor or acceptor. This versatility is especially relevant in the field of multifunctional or self-assembled catalysis.…”

Phosphorus as a Lewis Acid: CO2 Sequestration with Amidophosphoranes

“…The 31 P{ 1 H} NMR signal of 3 was observed as a doublet at d = À44.6 ppm ( 1 J PF = 679 Hz), and the corresponding 19 F resonance was seen at d = À44.4 ppm. [14] The exposure of a bright-yellow THF solution of 3 to 1 atm of CO 2 at ambient temperature results in its immediate discoloration, and NMR analysis performed shortly thereafter indicates complete conversion to a new species (4). The X-ray structure of 3 confirmed this formulation, demonstrating a distorted trigonal bipyramidal geometry at P, which is contained within a strained four-membered ring ( Figure 1).…”

“…The C À C bonds within the anilido ring are similar to those within neighboring Ph rings, in contrast to the dearomatization observed within metal complexes of the amidophosphine ligand. [14] The exposure of a bright-yellow THF solution of 3 to 1 atm of CO 2 at ambient temperature results in its immediate discoloration, and NMR analysis performed shortly thereafter indicates complete conversion to a new species (4). The 1 H NMR spectrum of 4 shows a singlet N-methyl resonance at d = 3.15 ppm, and the loss of its coupling to both P and F is consistent with rupture of the PÀN bond within 3 to accommodate CO 2 .…”

Ru(II) xantphos complex as an efficient catalyst in transfer hydrogenation of carbonyl compounds

“…Ru-P^N^P and Ru-P^O^P systems were found to be active and selective catalytic systems for wide range of substrates. Looking for an efficient and easily accessible complex, bis (phosphine) and mixed donor phosphine-amine complexes Ru II (P^N) and Ru II (P^N^N) have showed highly efficient catalysts for the hydrogenation of esters to alcohols (or conversely, the dehydrogenative coupling of alcohols to form esters) [21,22]. More recently, xantphos pincer complexes of the Ru [23] have also been reported to catalyze the transfer hydrogenation of carbonyl bonds with a high efficiency.…”