Stereochemical control of the exchange of hydrogen atoms between hydride and dihydrogen ligands in the complexes [M(.eta.2-H2)(H)(meso- or rac-tetraphos-1)]+, M = Fe, Os

Bautista, Maria T.; Earl, K. A.; Maltby, Patricia A.; Morris, Robert H.

doi:10.1021/ja00220a065

Cited by 46 publications

(30 citation statements)

References 3 publications

(4 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The trans-hydrides are diastereotopic due to the presence of the amine group. Complexes with inequivalent trans-dihydrides are rare: trans-FeH2(meso-tetraphos) has JHH 18 Hz 45,46 while cis dihydrides usually have JHH in the range 13-21 Hz. 7,26,[47][48][49] The 118 Hz 2 JPP of 3 is of similar magnitude to that of 2 ( 2 JPP 136 Hz) which has trans phosphorus nuclei in a mer P-N-P' configuration on the metal center 7 indicating that the ligand in 3 is also in the mer configuration as shown in Scheme 2.…”

Section: Introductionmentioning

confidence: 99%

Ketone Asymmetric Hydrogenation Catalyzed by P-NH-P′ Pincer Iron Catalysts: An Experimental and Computational Study

et al. 2016

Self Cite

View full text Add to dashboard Cite

Always cite the published version, so the author(s) will receive recognition through services that track citation counts, e.g. Scopus. If you need to cite the page number of the author manuscript from TSpace because you cannot access the published version, then cite the TSpace version in addition to the published version using the permanent URI (handle) found on the record page.ABSTRACT: Our group previously reported the development of iron carbonyl catalysts bearing chiral tridentate P-N-P' ligands for the asymmetric hydrogenation of prochiral ketones in THF. An NMR study into the activation process identified the amine hydride alkoxide complexes Fe(P-NH-P')(CO)(H)(OR 1 ) with R 1 = Me, tBu or tAmyl and P-NH-P' = PPh2CH2CH2NHCH2CH2PiPr2 or (S,S)-PPh2CHPhCHMeNHCH2CH2PCy2. These still required treatment with excess KOtBu and H2(g) to be catalytically active in THF. Both experimental methods and Density Functional Theory (DFT) calculations were used to show that this treatment leads to the formation of a hydride amide complex Fe(P-N-P')(CO)(H) which reacts with dihydrogen to form cis and trans dihydride complexes Fe(P-NH-P')(CO)(H)2, identified by NMR spectroscopy. In the presence of KOtBu, NaOtBu or KOtBu/2,2,2-cryptand and H2(g), these species are active for the catalytic hydrogenation of acetophenone, while in the absence of H2(g), inactive Fe(0) complexes are formed. Ketone hydrogenation is proposed to occur in an outer sphere stepwise process and this enantio-determining step has been modeled by DFT. The calculations suggest that the energy barriers for either hydride attack on the ketone, or dihydrogen splitting either to the nitrogen of the amide complex in the inner coordination sphere or to the oxygen of an alkoxide group in the outer sphere are similar and that either hydride transfer or dihydrogen splitting could determine the turn-over frequency depending of the nature of the ketone.

show abstract

Section: Introductionmentioning

confidence: 99%

Ketone Asymmetric Hydrogenation Catalyzed by P-NH-P′ Pincer Iron Catalysts: An Experimental and Computational Study

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…25 The trans geometry in these compounds may limit their reactivity by suppressing processes that require cis-disposed valencies, although cis-iron(II) complexes of bidentate and meso isomers of linear tetradentate phosphines are also formed on occasion. 23,[25][26][27][28][29][30] Ligand modifications can introduce strain, as well as control the geometry and configuration of late metal polyphosphine complexes. One approach involves replacing the central ethylene unit in DPPEPE with a methylene to shorten the ligand backbone and provide the ligand Ph 2 PCH 2 CH 2 PPhCH 2 PPhCH 2 -CH 2 PPh 2 (DPPEPM, Chart 1).…”

Section: ' Introductionmentioning

confidence: 99%

Synthesis of Monomeric Fe(II) and Ru(II) Complexes of Tetradentate Phosphines

Jana¹,

Ellern²,

Pestovsky³

et al. 2011

Inorg. Chem.

View full text Add to dashboard Cite

rac-Bis [{(diphenylphosphino)ethyl}-phenylphosphino]methane (DPPEPM) reacts with iron(II) and ruthenium(II) halides to generate complexes with folded DPPEPM coordination. The paramagnetic, fivecoordinate Fe(DPPEPM)Cl2 (1) in CD2Cl2 features a tridentate binding mode as established by 31P{1H} NMR spectroscopy. Crystal structure analysis of the analogous bromo complex, Fe(DPPEPM)Br2 (2) revealed a pseudo-octahedral, cis-α geometry at iron with DPPEPM coordinated in a tetradentate fashion. However, in CD2Cl2solution, the coordination of DPPEPM in 2 is similar to that of 1 in that one of the external phosphorus atoms is dissociated resulting in a mixture of three tridentate complexes. The chloro ruthenium complex cis-Ru(κ4-DPPEPM)Cl2 Multidentate ligands are often used to provide stabilized coordination complexes through the chelate effect. At the same time, the structure of a polydentate ligand provides means to control the bite angle, chelate ring size, and stereochemistry. The resulting electronic and steric effects can be used to enhance the reactivity of a metal center. In well-studied organometallic examples, ansa-metallocenes 1-3 and constrained-geometry compounds 4-9 provide enhanced reactivity in olefin polymerization and bond activation, while inhibiting disproportionation reactions. Similarly, bidentate phosphines enforce cis coordination geometries, even though trans configurations might be sterically or electronically preferred, and tridentate phosphines such as MeSi (CH 2 24 and FeCl 2 (DHPePE) 2 (DHPePE = 1,2-bis(bis(hydroxypropyl)phosphino)ethane). 25 The trans geometry in these compounds may limit their reactivity by suppressing processes that require cis-disposed valencies, although cis-iron(II) complexes of bidentate and meso isomers of linear tetradentate phosphines are also formed on occasion. 23,[25][26][27][28][29][30] Ligand modifications can introduce strain, as well as control the geometry and configuration of late metal polyphosphine complexes. One approach involves replacing the central ethylene unit in DPPEPE with a methylene to shorten the ligand backbone and provide the ligand

show abstract

“…The C1-ligand in trans-RuHClL is substituted for a CH3CN or PMe2Ph ligand in the presence of NaBF4 or NaPF6 in THF solvent (reaction [14]). …”

Section: Nmr Properties Of the Dihydrogen Complexes Trans-mentioning

confidence: 99%

“…The preliminary report of our work (14) described how the complexes trans-[M(H2)(~)LIf, M = Fe, Os, L = meso-tet-1, held the H2 and H ligands trarzs to each other so that no H-atom exchange occurred, while for the complex cis-a-[OsH3(ractet-l)]' there was rapid exchange of the H atoms. The present work describes in full detail the properties of the Fe and 0 s Can.…”

Section: Introductionmentioning

confidence: 97%

New dihydrogen complexes: the synthesis and spectroscopic properties of iron(II), ruthenium(II), and osmium(II) complexes containing the meso-tetraphos-1 ligand

Bautista¹,

Earl²,

Maltby³

et al. 1994

Can. J. Chem.

View full text Add to dashboard Cite

Can. J. Chem. 72,547 (1994). The synthesis and properties of dihydrogen complexes trans-[MH(H2)L]+, M = Fe, Ru, Os, which contain the ligand mesotetraphos-1, S,R-Ph2PCH2CH2P(Ph)CH2CH2P(Ph)CH2CH2PPh2 (L) are described. There are interesting possibilities of isomerism in such trans complexes because the axial binding sites at the metal are different, one being surrounded by four phenyl groups and the other by two phenyl groups. The osmium complex is prepared in an unusual reaction of ci.~-p-Os(Cl)~L with HI, (1 atm) and NaBPh4 (1 mol) in THF or by the reaction of trans-OsH(C1)L with NaBPh4 and H2. The iron and ruthenium complexes were made by a reaction of HBF4 with complexes t r a n~-M ( H )~L that have inequivalent trans hydrides. The ruthenium complex was also prepared starting from isomers of t r a n s -R U H ( C~) L .~T~~ H-H distance in the rapidly spinning dihydrogen ligand has been calculated from Tl(min) data to be 0. [Traduit par la rtdaction]

show abstract

Stereochemical control of the exchange of hydrogen atoms between hydride and dihydrogen ligands in the complexes [M(.eta.2-H2)(H)(meso- or rac-tetraphos-1)]+, M = Fe, Os

Cited by 46 publications

References 3 publications

Ketone Asymmetric Hydrogenation Catalyzed by P-NH-P′ Pincer Iron Catalysts: An Experimental and Computational Study

Ketone Asymmetric Hydrogenation Catalyzed by P-NH-P′ Pincer Iron Catalysts: An Experimental and Computational Study

Synthesis of Monomeric Fe(II) and Ru(II) Complexes of Tetradentate Phosphines

New dihydrogen complexes: the synthesis and spectroscopic properties of iron(II), ruthenium(II), and osmium(II) complexes containing the meso-tetraphos-1 ligand

Contact Info

Product

Resources

About