Crystal structure of diaqua[tris(2-aminoethyl)amine]cobalt(III) tris(trifluoromethanesulfonate), [Co(tren)(OH2)2](CF3SO3)3

Düpre, Y.; Bartscherer, Erik; Sander, Jürgen; Hüch, Volker; Hegetschweiler, K.

doi:10.1515/ncrs-1999-0354

Cited by 4 publications

(3 citation statements)

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“…The differentiation between H E /H F or H A /H D is based on the different 1 H− 1 H coupling constants of 13 Hz (geminal), and 13, 6, 5, and 0 Hz (vicinal). These values correspond well to the torsional H−C−C−H angles of 162°, 44°, 41°, and 77°, respectively, observed in the X-ray structure . The pH-dependence of the 1 H NMR signals shown in Figure e exhibits only two resonances with a monotonic shift toward lower frequency upon deprotonation.…”

Section: Resultssupporting

confidence: 78%

Spin−Orbit-Induced Anomalous pH-Dependence in ¹H NMR Spectra of Co^III Amine Complexes: A Diagnostic Tool for Structure Elucidation

et al. 2004

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The pH-dependent (1)H NMR characteristics of a series of Co(III)-(polyamin)-aqua and Co(III)-(polyamin)-(polyalcohol) complexes, [Co(tach)(ino-kappa(3)-O(1,3,5))](3+) (1(3+)), [Co(tach)(ino-kappa(3)-Omicron(1,2,6))](3+) (2(3+)), [Co(tach)(taci-kappa-Nu(1)-kappa(2)-O(2,6))](3+) (3(3+)), [Co(ditame)(H(2)O)](3+) (4(3+)), and [Co(tren)(H(2)O)(2)](3+) (5(3+)), were studied in D(2)O by means of titration experiments (tach = all-cis-cyclohexane-1,3,5-triamine, ino = cis-inositol, taci = 1,3,5-triamino-1,3,5-trideoxy-cis-inositol, tren = tris(2-aminoethyl)amine, ditame = 2,2,6,6-tetrakis-(aminomethyl)-4-aza-heptane). A characteristic shift was observed for H(-C) hydrogen atoms in the alpha-position of a coordinated amino group upon deprotonation of a coordinated oxygen donor. For a cis-H-C-N-Co-O-H arrangement, deprotonation of the oxygen donor resulted in an additional shielding (shift to lower frequency) of the H(-C) proton, whereas for a trans-H-C-N-Co-O-H arrangement, deprotonation resulted in a deshielding (shift to higher frequency). The effect appears to be of rather general nature: it is observed for primary (1(3+)-5(3+)), secondary (4(3+)), and tertiary (5(3+)) amino groups, and for the deprotonation of an alcohol (1(3+)-3(3+)) or a water (4(3+), 5(3+)) ligand. Spin-orbit-corrected density functional calculations show that the high-frequency deprotonation shift for the trans-position is largely caused by a differential cobalt-centered spin-orbit effect on the hydrogen nuclear shielding. This effect is conformation dependent due to a Karplus-type behavior of the spin-orbit-induced Fermi-contact shift and thus only significant for an approximately antiperiplanar H-C-N-Co arrangement. The differential spin-orbit contribution to the deprotonation shift in the trans-position arises from the much larger spin-orbit shift for the protonated than for the deprotonated state. This is in turn due to a trans-effect of the deprotonated (hydroxo or alkoxo) ligand, which weakens the trans Co-N bond and thereby interrupts the Fermi-contact mechanism for transfer of the spin-orbit-induced spin polarization to the hydrogen nucleus in question. The unexpectedly large long-range spin-orbit effects found here for 3d metal complexes are traced back to small energy denominators in the perturbation theoretical expressions of the spin-orbit shifts.

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Section: Resultssupporting

confidence: 78%

Spin−Orbit-Induced Anomalous pH-Dependence in ¹H NMR Spectra of Co^III Amine Complexes: A Diagnostic Tool for Structure Elucidation

et al. 2004

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“…Unfortunately, a direct comparison of the molecular structure of 1[Rh(H 2 O) 2 ] 3+ and 1[Co(H 2 O) 2 ] 3+ is not possible. A crystal structure of the triflate salt of 1[Co(H 2 O) 2 ] 3+ has been published, but the corresponding structure of 1[Rh(H 2 O) 2 ] 3+ is not known. While our efforts to obtain a crystal structure of this complex were not successful, we could grow single crystals of the corresponding chloro complex [Rh(tren)Cl 2 ] 2 [ZnCl 4 ].…”

Section: Resultsmentioning

confidence: 99%

Characteristic Spin−Orbit Induced ¹H(CH₂) Chemical Shifts upon Deprotonation of Group 9 Polyamine Aqua and Alcohol Complexes

et al. 2009

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The recently observed nonintuitive pH dependence of methylene (1)H chemical shifts in cobalt(III) polyamine complexes upon deprotonation of coordinated aqua or (poly)alcohol coligands (J. Am. Chem. Soc. 2004, 126, 6728) was attributed to differential spin-orbit effects on the (1)H shifts transmitted over three bonds from the cobalt low-spin d(6) center. These remarkably large spin-orbit effects due to the comparably light Co center have now been examined closely by comparative computations for homologous Rh and Ir complexes, as well as by NMR titrations for a Rh complex. While larger spin-orbit effects (proportional to Z(2)) would have been expected for the heavier metal centers, the characteristic (1)H deshieldings upon deprotonation of [Rh(tren)(OH(2))(2)](3+) [tren = tris(2-aminoethyl)-amine] turn out to be smaller than for the Co homologous Co complex. Systematic computational studies ranging from smaller models to the full complexes confirm these results and extend them to the Ir homologues. Closer analysis indicates that the spin-orbit shift contributions do not follow the expected Z(2) behavior but are modulated dramatically by increasing energy denominators in the perturbation expressions. This is related to the increasing ligand-field splitting from 3d to 4d to 5d system, leading to almost identical differential spin-orbit shifts for the Co and Rh complexes and to only moderately larger effects for the Ir complex (by a factor of about two). Moreover, the differential nonspin-orbit deprotonation shifts cancel the spin-orbit induced contributions largely in the Rh complex, leading to the experimentally observed inverted behavior. The full multidentate polyamine complexes studied experimentally exhibit different three- and four-bond Fermi-contact pathways for transmission of the spin-orbit (1)H shifts. The novel four-bond pathways have different conformational dependencies than the Karplus-like three-bond pathways established previously. Both types of contributions are of similar magnitude. The (1)H NMR deprotonation shift patterns of [Ir(tren)(OH(2))(2)](3+) have been predicted computationally.

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“…30 Bis(amino acidate)cobalt(III) complexes can be obtained by air oxidation of dmso solutions containing cobalt(II), bipy and the free amino acid. 31 The structures have 33 The Co^N bonds trans to nitrogen are longer than those trans to the other ligands. Cobalt(III) complexes of a new tetrapodal ligand (3) have been synthesised; this ligand restricts rearrangements in dissociative substitution reactions and limits the lifetime of intermediates.…”

Section: Nitrogen Donorsmentioning

confidence: 99%

14 Iron, cobalt and nickel

Cotton¹

2000

Annu. Rep. Prog. Chem., Sect. A

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Crystal structure of diaqua[tris(2-aminoethyl)amine]cobalt(III) tris(trifluoromethanesulfonate), [Co(tren)(OH2)2](CF3SO3)3

Cited by 4 publications

References 2 publications

Spin−Orbit-Induced Anomalous pH-Dependence in ¹H NMR Spectra of Co^III Amine Complexes: A Diagnostic Tool for Structure Elucidation

Spin−Orbit-Induced Anomalous pH-Dependence in ¹H NMR Spectra of Co^III Amine Complexes: A Diagnostic Tool for Structure Elucidation

Characteristic Spin−Orbit Induced ¹H(CH₂) Chemical Shifts upon Deprotonation of Group 9 Polyamine Aqua and Alcohol Complexes

14 Iron, cobalt and nickel

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Crystal structure of diaqua[tris(2-aminoethyl)amine]cobalt(III) tris(trifluoromethanesulfonate), [Co(tren)(OH2)2](CF3SO3)3

Cited by 4 publications

References 2 publications

Spin−Orbit-Induced Anomalous pH-Dependence in 1H NMR Spectra of CoIII Amine Complexes: A Diagnostic Tool for Structure Elucidation

Spin−Orbit-Induced Anomalous pH-Dependence in 1H NMR Spectra of CoIII Amine Complexes: A Diagnostic Tool for Structure Elucidation

Characteristic Spin−Orbit Induced 1H(CH2) Chemical Shifts upon Deprotonation of Group 9 Polyamine Aqua and Alcohol Complexes

14 Iron, cobalt and nickel

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Spin−Orbit-Induced Anomalous pH-Dependence in ¹H NMR Spectra of Co^III Amine Complexes: A Diagnostic Tool for Structure Elucidation

Spin−Orbit-Induced Anomalous pH-Dependence in ¹H NMR Spectra of Co^III Amine Complexes: A Diagnostic Tool for Structure Elucidation

Characteristic Spin−Orbit Induced ¹H(CH₂) Chemical Shifts upon Deprotonation of Group 9 Polyamine Aqua and Alcohol Complexes