20491-53-6Relevant articles and documents
Parallels between Metal-Ligand Cooperativity and Frustrated Lewis Pairs
Habraken, Evi R. M.,Jupp, Andrew R.,Brands, Maria B.,Nieger, Martin,Ehlers, Andreas W.,Slootweg, J. Chris
, p. 2436 - 2442 (2019)
Metal ligand cooperativity (MLC) and frustrated Lewis pair (FLP) chemistry both feature the cooperative action of a Lewis acidic and a Lewis basic site on a substrate. A lot of work has been carried out in the field of FLPs to prevent Lewis adduct formation, which often reduces the FLP reactivity. Parallels are drawn between the two systems by looking at their reactivity with CO2, and we explore the role of steric bulk in preventing dimer formation in MLC systems.
Enantioselective addition of secondary phosphines to methacrylonitrile: Catalysis and mechanism
Sadow, Aaron D.,Togni, Antonio
, p. 17012 - 17024 (2005)
A highly enantioselective intermolecular hydrophosphination reaction is described. The (Pigiphos)-nickel(II)-catalyzed reaction of secondary phosphines and methacrylonitrile gives chiral 2-cyanopropylphosphines in good yield and high enantiomeric excess (ee's up to 94%; (R)-(S)-Pigiphos = bis{(R)-1-[(S)-2-(diphenylphosphino)ferrocenyl]ethyl}cyclohexylphos phine). We propose a mechanism involving coordination of methacrylonitrile to the dicationic nickel catalyst followed by 1,4-addition of the phosphine, and then, rate-determining proton transfer. This mechanism is supported by (a) the experimentally determined rate law (rate = K[Ni][methacrylonitrile][t-Bu 2PH]), (b) a large primary deuterium isotope effect K H/KD = 4.6(1) for the addition of t-Bu2PH(D) at 28.3°C in toluene-d8, (c) the isolation and characterization of the species [Ni(K3-Pigiphos)(KN-methacrylonitrile)]2+, and (d) DFT calculations of model compounds.
A wacker-type strategy for the synthesis of unsymmetrical POCsp3E-nickel pincer complexes
Mangin, Lo?c P.,Michaud, Guillaume,Zargarian, Davit
, p. 4006 - 4018 (2020)
ECE-type pincer complexes have evolved into a diverse family of compounds possessing interesting structural/ bonding features, reactivities, and practical applications. An important factor promoting the growth of pincer chemistry is the availability of versatile synthetic pathways that give access to ever-diverse pincer complexes. This report describes the synthesis of pincer-Ni complexes possessing the following features: a central Ni-Csp3 linkage, two different peripheral donor moieties, and two differently sized metallacycles. The synthetic methodology reported herein is based on the reactivity of a phosphinite derived from 2-vinylphenol. Stirring the substrate 2-CH2=CH-C6H4-OP(i-Pr)2, 1, with the NiII precursor {(i-PrCN)NiBr2}n and Et3N at room temperature gave the 6,5-POCsp3PO-type pincer complex {κO,κC,κP-2-[(i-Pr)2P(O)CH2CH]-C6H4-OP(i-Pr)2}NiBr, 2. Conducting this reaction in the presence of an excess of 1 hinders the formation of 2, giving instead the nickellacyclopropane complex {κC,κ,κP-2-[(2-CH2=CH-C6H4O)P(i-Pr)2CHCH]-C6H4-OP(i-Pr)2}NiBr, 3, whereas introducing a second, stronger nucleophile into the reaction mixture leads to the formation of pincer complexes featuring rare 4-membered metallacycles. For instance, using HNR(R′) as nucleophile gave the 6,4-POCsp3N-type pincer complexes {κN,κC,κP-2-[R(R′)NCH2CH]-C6H4-OP(iPr)2}NiBr (NR(R′) = N-morpholyl, 4; NPh(Et), 5; NH(i-Pr), 6; NH(Ph), 7; NH(Cy), 8; NH(t-Bu), 9), whereas using HPR2 as nucleophile led to the 6,4-POCsp3P-type pincer complexes {κP,κC,κP′-2-[R2PCH2CH]-C6H4-OP(i-Pr)2}NiBr (R = i-Pr, 10; iPh, 11). Single crystal diffraction studies have established the solid-state structures of complexes 2-11. All the pincer complexes reported here feature 6-membered metallacycles defined by the phosphinite moiety, while the phosphine-oxide moiety in 2 defines a 5-membered metallacycle and 4-membered metallacycles form by the coordination of the amine moieties in 4-9 and the phosphines in 10 and 11. Cyclic voltammetry measurements on complexes 2, 4-6, 10, and 11 have shown that these pincer-Ni complexes undergo facile one-electron oxidation.
N,N-BIS(2-DIALKYLPHOSPHINOETHYL)AMINE-BORANE COMPLEX AND PRODUCTION METHOD THEREFOR, AND METHOD FOR PRODUCING RUTHENIUM COMPLEX CONTAINING N,N-BIS(2-DIALKYLPHOSPHINOETHYL)AMINE AS LIGAND
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Paragraph 0164; 0165-0169, (2019/02/19)
The purpose of the present invention is to provide an N,N-bis(2-dialkylphosphinoethyl)amine-borane complex which is a ruthenium complex that exhibits excellent catalytic activity in a hydrogenation reaction, etc., and a production method therefor, and a method for efficiently producing a ruthenium complex containing N,N-bis(2-dialkylphosphinoethyl)amine as a ligand. The present invention is capable of efficiently producing an amine-borane complex (3) by reacting an oxazolidinone compound (1) with a dialkylphosphine-borane compound (2) in the presence of a base. The present invention is also capable of efficiently producing a ruthenium complex (5) by reacting the amine-borane complex (3) with a ruthenium compound (4) in the presence of an amine. (In the formula, a solid line, a dashed line, B, C, H, L1-L3, LG, n, N, O, P, Ru, X, and R1-R10 are as defined in the description.)
Role of Phosphine Sterics in Strained Aminophosphine Chelate Formation
Bowes, Eric G.,Dawson Beattie,Love, Jennifer A.
supporting information, p. 2925 - 2929 (2019/03/02)
The preparation of four-membered aminophosphine (PN) chelates from common metal precursors has largely evaded realization because of the ring strain associated with these species. We report a straightforward approach to the synthesis of such PN metallacycles using simple α-PN ligands analogous to the popular class of small-bite-angle diphosphinomethane ligands. It is demonstrated that bulky phosphine substituents are important to the formation of these chelates.
A Universally Applicable Methodology for the Gram-Scale Synthesis of Primary, Secondary, and Tertiary Phosphines
Rinehart, N. Ian,Kendall, Alexander J.,Tyler, David R.
supporting information, p. 182 - 190 (2018/02/06)
Although organophosphine syntheses have been known for the better part of a century, the synthesis of phosphines still represents an arduous task for even veteran synthetic chemists. Phosphines as a class of compounds vary greatly in their air sensitivity, and the misconception that it is trivial or even easy for a novice chemist to attempt a seemingly straightforward synthesis can have disastrous results. To simplify the task, we have previously developed a methodology that uses benchtop intermediates to access a wide variety of phosphine oxides (an immediate precursor to phosphines). This synthetic approach saves the air-free handling until the last step (reduction to and isolation of the phosphine). Presented herein is a complete general procedure for the facile reduction of phosphonates, phosphinates, and phosphine oxides to primary, secondary, and tertiary phosphines using aluminum hydride reducing agents. The electrophilic reducing agents (iBu)2AlH and AlH3 were determined to be vastly superior to LiAlH4 for reduction selectivity and reactivity. Notably, it was determined that AlH3 is capable of reducing the exceptionally resistant tricyclohexylphosphine oxide, even though LiAlH4 and (iBu)2AlH were not. Using this new procedure, gram-scale reactions to synthesize a representative range of primary, secondary, and tertiary phosphines (including volatile phosphines) were achieved reproducibly with excellent yields and unmatched purity without the need for a purification step.
Rapid Metal-Free Formation of Free Phosphines from Phosphine Oxides
Provis-Evans, Cei B.,Emanuelsson, Emma A. C.,Webster, Ruth L.
supporting information, p. 3999 - 4004 (2018/09/21)
A rapid method for the reduction of secondary phosphine oxides under mild conditions has been developed, allowing simple isolation of the corresponding free phosphines. The methodology involves the use of pinacol borane (HBpin) to effect the reduction while circumventing the formation of a phosphine borane adduct, as is usually the case with various other commonly used borane reducing agents such as borane tetrahydrofuran complex (BH3?THF) and borane dimethyl sulfide complex (BH3?SMe2). In addition, this methodology requires only a small excess of reducing agent and therefore compares favourably not just with other borane reductants that do not require a metal co-catalyst, but also with silane and aluminium based reagents. (Figure presented.).
Synthesis and reactivity of substituted alkoxymethylphosphonites and their derivatives
Prishchenko, Andrey A.,Livantsov, Mikhail V.,Novikova, Olga P.,Livantsova, Ludmila I.,Petrosyan, Valery S.
experimental part, p. 281 - 289 (2012/07/28)
Alkoxy-substituted methylphosphonites and their derivatives are prepared using an organomagnesium method of synthesizing the organophosphorus compounds and alkoxymethylation of various PH acids and their derivatives. Also, certain properties of these promising compounds as important precursors of new functionalized organophosphorue compounds with alkoxymethyl fragments are presented.
Identification of a four-center intermediate in a Grignard addition reaction to a P-S bond
Baccolini, Graziano,Boga, Carla,Mazzacurati, Marzia
, p. 12595 - 12600 (2008/03/14)
The reaction between tert-butylmagnesium chloride (or tert-pentylmagnesium chloride) and the particular phosphorus-sulfur bond of a benzothiadiphospholic system showed, for the first time, evidence of formation of intermediates with a four-center structure. The possibility, for the phosphorus atom, to have very stable hypervalent coordinations makes it possible to observe its hypervalent states during the course of a reaction. The benzothiadiphosphole, with its bicyclic folded structure, further stabilizes the hypervalent coordinations thus making the intermediates sufficiently stable to be detected during the course of the reaction by 31P NMR spectroscopy, which revealed the nature and the stability of the species involved in this reaction, carried out also using other Grignard reagents.
Highly effective pincer-ligated iridium catalysts for alkane dehydrogenation. DFT calculations of relevant thermodynamic, kinetic, and spectroscopic properties
Zhu, Keming,Achord, Patrick D.,Zhang, Xiawei,Krogh-Jespersen, Karsten,Goldman, Alan S.
, p. 13044 - 13053 (2007/10/03)
The p-methoxy-substituted pincer-ligated iridium complexes, (MeO- tBuPCP)IrH4 (RPCP = κ3-C 6H3-2,6-(CH2PR2)2) and (MeO-iPrPCP)IrH4, are found to be highly effective catalysts for the dehydrogenation of alkanes (both with and without the use of sacrificial hydrogen acceptors). These complexes offer an interesting comparison with the recently reported bis-phosphinite POCOP (RPOCOP = κ3-C6H3-2,6-(OPR2) 2) pincer-ligated catalysts, which also show catalytic activity higher than unsubstituted PCP analogues (Goettker-Schnetmann, I.; White, P.; Brookhart, M. J. Am. Chem. Soc. 2004, 126, 1804). On the basis of νCO values of the respective CO adducts, the MeO-PCP complexes appear to be more electron-rich than the parent PCP complexes, whereas the POCOP complexes appear to be more electron-poor. However, the MeO-PCP and POCOP ligands are calculated (DFT) to show effects in the same directions, relative to the parent PCP ligand, for the kinetics and thermodynamics of a broad range of reactions including the addition of C-H and H-H bonds and CO. In general, both ligands favor (relative to unsubstituted PCP) addition to the 14e (pincer)Ir fragments but disfavor addition to the 16e complexes (pincer)IrH2 or (pincer)-Ir(CO). These kinetic and thermodynamic effects are all largely attributable to the same electronic feature: O → C(aryl) π-donation, from the methoxy or phosphinito groups of the respective ligands. DFT calculations also indicate that the kinetics (but not the thermodynamics) of C-H addition to (pincer)Ir are favored by σ-withdrawal from the phosphorus atoms. The high νCO value of (POCOP)Ir(CO) is attributable to electrostatic effects, rather than decreased Ir-CO π-donation or increased OC-Ir σ-donation.
