T1 Spin decoupling effects on the lineshapes of NMR spin—spin multiplets

Polak, M.

doi:10.1016/0009-2614(74)89126-8

Cited by 11 publications

(6 citation statements)

References 15 publications

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“…It is noteworthy that no 31 P− 1 H coupling is visible (recall the large ∼35 Hz splitting for the hydride triplet of 2j + ). Such apparent decoupling, known as T 1 spin decoupling, was quantitatively described nearly 35 years ago, but relatively few unambiguous examples have since appeared in the literature. The hydride resonance of 2j + / 2i can be described as the A subsystem of an AX 2 system, where X 2 are in close proximity to a metal.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, Electrochemistry, and Reactivity of Half-Sandwich Ruthenium Complexes Bearing Metallocene-Based Bisphosphines

Shaw¹,

Norton²,

Buccella³

et al. 2009

Organometallics

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The bimetallic complexes CpRu(P-P)X [Cp=η 5 -C 5 H 5 ; X=Cl, H; P-P=dppf (1,1 0 -bis(diphenylphosphino)ferrocene), dppr (1,1 0 -bis(diphenylphosphino)ruthenocene), dppo (1,1 0 -bis(diphenylphosphino)-osmocene), dippf (1,1 0 -bis(diisopropylphosphino)ferrocene), dcpf (1,1 0 -bis(dicyclohexylphosphino)ferrocene)], Cp*Ru(P-P)X [Cp*=η 5 -C 5 Me 5 ; X=Cl, H; P-P=dppf, dippf, dppomf (1,1 0 -bis(diphenylphosphino) octamethylferrocene), dppc (1,1 0 -bis(diphenylphosphino)cobaltocene)], [Cp*Ru(P-P)X] + (X=H, CCPh; P-P=dppc + ), and [Cp*Ru(P-P)L] 2+ (L= CH 3 CN, t-BuCN; P-P= dppc + ) have been synthesized. Most of the chloride and hydride complexes have been studied by cyclic voltammetry. The X-ray structures of [Cp*Ru(dppc)CH 3 CN][PF 6 ] 2 and [Cp*Ru(dppc)CCPh][PF 6 ] have been determined. Protonation of [Cp*Ru(dppc)CCPh] + gives the vinylidene complex [Cp*Ru(dppc)CCHPh] 2+ . The Co(III/II) potential of the dppc + ligand undergoes a cathodic shift upon coordination in [Cp*Ru-(dppc)H] + and an anodic shift upon coordination in [Cp*Ru(dppc)CH 3 CN] 2+ . The 1 H NMR spectrum of Cp*Ru(dppc)H is consistent with its formulation as a Co(II)/Ru(II) complex. As gauged by their reactivity toward iminium cations, the hydride complexes are poor hydride donors; proton and electron transfer are dominant. CpRu(dippf)H and CpRu(dcpf)H deprotonate iminium cations with acidic R-hydrogens. Cp*Ru(dppc)H is oxidized by the N-(benzylidene)pyrrolidinium cation, giving [Cp*Ru-(dppc)H] + and the vicinal diamine 1,2-bis(N-pyrrolidino)-1,2-diphenylethane. Most of the hydride complexes give trans-dihydride cations upon protonation; an exception is [Cp*Ru(dppc)H] + , which forms a dihydrogen complex [Cp*Ru(dppc)(H 2 )] 2+ with surprising kinetic stability. This dihydrogen complex is more acidic and less thermodynamically stable than its dihydride isomer. The H 2 ligand in [Cp*Ru(dppc)-(H 2 )] 2+ is readily replaced by nitriles; the reaction with t-BuCN occurs by a dissociative mechanism.

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Section: Resultsmentioning

confidence: 99%

Synthesis, Electrochemistry, and Reactivity of Half-Sandwich Ruthenium Complexes Bearing Metallocene-Based Bisphosphines

Shaw¹,

Norton²,

Buccella³

et al. 2009

Organometallics

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“…7 Hz for such a group. However, the signal is somewhat broad, and a short Tt of the coupled CH could induce an apparent reduction of the splitting on the methyl group (Navon & Polak, 1974). The complete identification of methyl resonances was achieved also for PSTI II, whose spectrum is shown in Figure 4B.…”

Section: Resultsmentioning

confidence: 81%

pH and temperature effects on the molecular conformation of the porcine pancreatic secretory trypsin inhibitor as detected by proton nuclear magnetic resonance

Marco¹,

Menegatti²,

Guarneri³

1982

Biochemistry

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1H NMR spectra of the porcine pancreatic secretory trypsin inhibitor (PSTI) have been recorded vs. pH and temperature. Of the two tyrosines, one titrates with a pK of 11.25, while the resonances from the other are pH insensitive in the investigated range 4.8 less than or equal to pH less than or equal to 12. This is consistent with PSTI having one Tyr solvent exposed (Tyr-20) and the other buried (Tyr-31). The resonances from the lysyl epsilon-CH2 protons titrate with a pK of 10.95. The titration is accompanied by a pronounced line broadening, which starts near pH 8.5. Between pH 11.5 and pH 12 the epsilon-CH2 resonances recover their low pH line width. Titration curves for the lysines and Tyr-20 reflect single proton ionization equilibria, suggesting that these residues do not interact among themselves. On the basis of double resonance experiments, combined with analysis of chemical shifts, spin-spin couplings, and line widths, all methyl resonances are identified and followed as functions of pH and temperature. The gamma-CH3 doublet from the N-terminal Thr-1 is assigned by comparison between spectra of forms I and II of the inhibitor, the latter lacking the first four residues of form I. The beta-CH3 resonance from Ala-7 is also assigned. Proton resonance parameters of methyl groups are shown to afford useful NMR probes for the characterization of local nonbonded interactions, microenvironments, and mobilities.

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“…As a further check a 4.5-atm 02 broadened spectrum of the aliphatic residue of p-diethoxybenzene is compared in Figure 1 with a spectrum computed as described before. 16 The agreement seems satisfactory. Accordingly, the apparent reduction of J is fully explained.…”

Section: Resultsmentioning

confidence: 85%

Nuclear magnetic resonance studies of the interaction of molecular oxygen with organic compounds

Polak¹

1974

J. Phys. Chem.

Self Cite

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Proton nmr line broadenings and chemical shifts due to dissolved molecular oxygen were measured for various organic compounds. After corrections for the extra broadening in spin-spin multiplets, due to 7\ spin decoupling effects, the observed oxygen-induced broadening was similar for all compounds studied. It was concluded that there was no complex formation between the oxygen and the organic molecules. Small oxygen-induced chemical shifts could be observed and some possibilities for their origin were discussed.

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T1 Spin decoupling effects on the lineshapes of NMR spin—spin multiplets

Cited by 11 publications

References 15 publications

Synthesis, Electrochemistry, and Reactivity of Half-Sandwich Ruthenium Complexes Bearing Metallocene-Based Bisphosphines

Synthesis, Electrochemistry, and Reactivity of Half-Sandwich Ruthenium Complexes Bearing Metallocene-Based Bisphosphines

pH and temperature effects on the molecular conformation of the porcine pancreatic secretory trypsin inhibitor as detected by proton nuclear magnetic resonance

Nuclear magnetic resonance studies of the interaction of molecular oxygen with organic compounds

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