New products in an old reaction: isomeric products from H2 addition to Vaska’s complex and its analogues

Hasnip, Sarah; Duckett, Simon B.; Sleigh, Christopher J.; Taylor, Diana R.; Barlow, Graham K.; Taylor, Mike

doi:10.1039/a905590h

Cited by 29 publications

(19 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[19] The 31 P NMR spectrum of 1 in CD 2 Cl 2 under H 2 thus shows one singlet at d = 6.1 ppm, whereas in the 1 H NMR spectrum the two hydride signals are at d = À7.5 and À18.9 ppm, showing 2 J-A C H T U N G T R E N N U N G (H,H) = 4.6 Hz, with 2 JA C H T U N G T R E N N U N G (H,P) = 17.8 and 15.2 Hz, respectively, values close to those reported for the related PPh 3 complex. [20] When the 2,6-dimethyl-substituted arylphosphane PPh 2 (2,6-Me 2 C 6 JA C H T U N G T R E N N U N G (P,P) = 349 Hz, typical for iridiumA C H T U N G T R E N N U N G (III) species bearing two trans phosphanes. [21] In the 1 H NMR spectrum the two cyclometalated CH 2 moieties appear as four signals in the d = 2.55-2.04 ppm range for nonequivalent protons coupled with H and P atoms, whereas the singlets at d = 1.85 and 1.76 ppm are for the two methyl groups.…”

Section: Resultsmentioning

confidence: 99%

CH Activation and CC Double Bond Formation Reactions in Iridium ortho‐Methyl Arylphosphane Complexes

Baratta

Ballico

Zotto

et al. 2007

Chemistry A European J

View full text Add to dashboard Cite

The Vaska-type iridium(I) complex [IrCl(CO){PPh(2)(2-MeC(6)H(4))}(2)] (1), characterized by an X-ray diffraction study, was obtained from iridium(III) chloride hydrate and PPh(2)(2,6-MeRC(6)H(3)) with R=H in DMF, whereas for R=Me, activation of two ortho-methyl groups resulted in the biscyclometalated iridium(III) compound [IrCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)] (2). Conversely, for R=Me the iridium(I) compound [IrCl(CO){PPh(2)(2,6-Me(2)C(6)H(3))}(2)] (3) can be obtained by treatment of [IrCl(COE)(2)](2) (COE=cyclooctene) with carbon monoxide and the phosphane in acetonitrile. Compound 3 in CH(2)Cl(2) undergoes intramolecular C-H oxidative addition, affording the cyclometalated hydride iridium(III) species [IrHCl(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}] (4). Treatment of 2 with Na[BAr(f) (4)] (Ar(f)=3,5-C(6)H(3)(CF(3))(2)) gives the fluxional cationic 16-electron complex [Ir(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}(2)][BAr(f) (4)] (5), which reversibly reacts with dihydrogen to afford the delta-agostic complex [IrH(CO){PPh(2)(2,6-CH(2)MeC(6)H(3))}{PPh(2)(2,6-Me(2)C(6)H(3))}][BAr(f)(4)] (6), through cleavage of an Ir-C bond. This species can also be formed by treatment of 4 with Na[BAr(f)(4)] or of 2 with Na[BAr(f)(4)] through C-H oxidative addition of one ortho-methyl group, via a transient 14-electron iridium(I) complex. Heating of the coordinatively unsaturated biscyclometalated species 5 in toluene gives the trans-dihydride iridium(III) complex [IrH(2)(CO){PPh(2)(2,6-MeC(6)H(3)CH=CHC(6)H(3)Me-2,6)PPh(2)}][BAr(f) (4)] (7), containing a trans-stilbene-type terdentate ligand, as result of a dehydrogenative carbon-carbon double bond coupling reaction, possibly through an iridium carbene species.

show abstract

Section: Resultsmentioning

confidence: 99%

CH Activation and CC Double Bond Formation Reactions in Iridium ortho‐Methyl Arylphosphane Complexes

Baratta

Ballico

Zotto

et al. 2007

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Subsequent investigations into the reactivity of IrCl(CO)(PPh 3 ) 2 revealed that, when the initial addition of parahydrogen was conducted at 298 K, a second hydridecontaining product was observed in addition to the usual product, which was only observable because of the enhancement afforded by the parahydrogen methodology [40]. This second product was revealed to be the product of hydrogen addition over the P-Ir-P axis of IrCl(CO)(PPh 3 ) 2 , rather than the usual addition over the Cl-Ir-CO axis, resulting in the formation of a previously unknown isomer of IrCl(H) 2 (CO)(PPh 3 ) 2 containing mutually cis phosphines (Fig.…”

Section: The Detection and Investigation Of Metal Hydride Speciesmentioning

confidence: 97%

Parahydrogen-based NMR methods as a mechanistic probe in inorganic chemistry

Duckett

Wood

2008

Coordination Chemistry Reviews

Self Cite

123

127

View full text Add to dashboard Cite

“…Spin polarization of order unity is attainable but only if H 2 is added to the substrate in a pairwise fashion. PHIP NMR spectroscopy has been employed to study mechanisms of both homogeneous and heterogeneous hydrogenation catalysis 7–10. Recent innovations have broadened the applicability of the technique 11–19.…”

mentioning

confidence: 99%

Shaped Ceria Nanocrystals Catalyze Efficient and Selective Para‐Hydrogen‐Enhanced Polarization

et al. 2015

View full text Add to dashboard Cite

Intense para-hydrogen-enhanced NMR signals are observed in the hydrogenation of propene and propyne over ceria nanocubes, nano-octahedra, and nanorods. The well-defined ceria shapes, synthesized by a hydrothermal method, expose different crystalline facets with various oxygen vacancy densities, which are known to play a role in hydrogenation and oxidation catalysis. While the catalytic activity of the hydrogenation of propene over ceria is strongly facet-dependent, the pairwise selectivity is low (2.4% at 375 °C), which is consistent with stepwise H atom transfer, and it is the same for all three nanocrystal shapes. Selective semi-hydrogenation of propyne over ceria nanocubes yields hyperpolarized propene with a similar pairwise selectivity of (2.7% at 300 °C), indicating product formation predominantly by a non-pairwise addition. Ceria is also shown to be an efficient pairwise replacement catalyst for propene.

show abstract

New products in an old reaction: isomeric products from H2 addition to Vaska’s complex and its analogues

Cited by 29 publications

References 12 publications

CH Activation and CC Double Bond Formation Reactions in Iridium ortho‐Methyl Arylphosphane Complexes

CH Activation and CC Double Bond Formation Reactions in Iridium ortho‐Methyl Arylphosphane Complexes

Parahydrogen-based NMR methods as a mechanistic probe in inorganic chemistry

Shaped Ceria Nanocrystals Catalyze Efficient and Selective Para‐Hydrogen‐Enhanced Polarization

Contact Info

Product

Resources

About