Applications of 95Mo NMR spectroscopy. XIII. Relaxation times of molybdenum compounds

Brownlee, Robert T. C.; O'connor, M. J.; Shehan, B. Philip; Wedd, Anthony G.

doi:10.1016/0022-2364(85)90191-x

Cited by 8 publications

(4 citation statements)

References 15 publications

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“…Bennett and co-workers, who recently published 14N data for the mono-to trisubstituted tungsten complexes with one aliphatic ligand, ícrí-butyl isocyanide, and one aromatic ligand, p-tolyl isocyanide, found the same trend for their compounds.5 They claim that the 14N nucleus in an aryl isocyanide complex is [14][15][16][17][18] ppm more shielded than that in an alkyl isocyanide complex. A III) shows that ligands with aliphatic R groups such as methyl, ethyl, «-butyl, or morpholinoethyl isocyanide have chemical shifts equal to those with aromatic R groups.…”

Section: Discussionmentioning

confidence: 94%

“…When two carbonyl groups in Mo(CO)6 are replaced by other monodentate ligands to form Mo(CO)4L2, deshielding of 31 ppm is found for dmpi, 29 ppm for trimethyl phosphite,12,13 300 ppm for triphenylphosphine,12,13 549 ppm for acetonitrile,12 and 805 ppm for pyridine. 17 The largest deshielding of 826 ppm is achieved with a bidentate ligand, 2-phenylazopyridine (2-pap). 18 The Mo(2-pap)3 complex has the most positive chemical shift known to date for a Mo(0) complex, +1502 ppm.…”

Section: Discussionmentioning

confidence: 99%

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Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes

Minelli¹,

Maley²

1989

Inorg. Chem.

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Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes

Minelli¹,

Maley²

1989

Inorg. Chem.

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“…Quadrupolar nuclei generally via the quadrupolar mechanism, i.e., the interaction of the nuclear quadrupole moment with fluctuating electric field gradients at the nucleus. Brownlee et al have measured the 95 Mo spin-lattice relaxation time constant, T 1 , at 4.7 T for a 0.5 M solution of 1 in CDCl 3 at 20 C to be 70.1 ms. 27,65 We investigated the possibility of relaxation in solution by the chemical shift anisotropy (CSA) mechanism, given the relatively small value of C Q ( 95 Mo) and the relatively anisotropic molybdenum CS tensor. If relaxation by CSA were dominant, one would expect an inverse scaling of T 1 ( 95 Mo) with the square of B 0 ,…”

Section: Resultsmentioning

confidence: 99%

A 95Mo and 13C solid-state NMR and relativistic DFT investigation of mesitylenetricarbonylmolybdenum(0) – a typical transition metal piano-stool complex

Bryce

Wasylishen

2002

Phys. Chem. Chem. Phys.

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The chemical shift (CS) and electric field gradient (EFG) tensors in the piano-stool compound mesitylenetricarbonylmolybdenum(0), 1, have been investigated via 95 Mo and 13 C solid-state magic-angle spinning (MAS) NMR as well as relativistic zeroth-order regular approximation density functional theory (ZORA-DFT) calculations. Molybdenum-95 (I ¼ 5/2) MAS NMR spectra acquired at 18.8 T are dominated by the anisotropic chemical shift interaction (O ¼ 775 AE 30 ppm) rather than the 2nd-order quadrupolar interaction (C Q ¼ À0.96 AE 0.15 MHz), an unusual situation for a quadrupolar nucleus. ZORA-DFT calculations of the 95 Mo EFG and CS tensors are in agreement with the experimental data. Mixing of appropriate occupied and virtual d-orbital dominated MOs in the region of the HOMO-LUMO gap are shown to be responsible for the large chemical shift anisotropy. The small, but non-negligible, 95 Mo quadrupolar interaction is discussed in terms of the geometry about Mo. Carbon-13 CPMAS spectra acquired at 4.7 T demonstrate the crystallographic and magnetic nonequivalence of the twelve 13 C nuclei in 1, despite the chemical equivalence of some of these nuclei in isotropic solutions. The principal components of the carbon CS tensors are determined via a Herzfeld-Berger analysis, and indicate that motion of the mesitylene ring is slow compared to a rate which would influence the carbon CS tensors (i.e. tens of ms). ZORA-DFT calculations reproduce the experimental carbon CS tensors accurately. Oxygen-17 EFG and CS tensors for 1 are also calculated and discussed in terms of existing experimental data for related molybdenum carbonyl compounds. This work provides an example of the information available from combined multi-field solid-state multinuclear magnetic resonance and computational investigations of transition metal compounds, in particular the direct study of quadrupolar transition metal nuclei with relatively small magnetic moments.

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“…Thus, less symmetric molecules have shorter relaxation time and, consequently spectra with broader lines are obtained. [22] On the other hand, the broadening of the signals can point to the presence of isomers showing close chemical shifts. Therefore, when IV and V are solubilised, two resonances are observed showing an important chemical shift difference between them ( δ > 100 ppm, entries 4 and 5 in Table 1), due to the partial nitrogen de-coordination of the bidentated N,O- oxazolinylphenolate ligand as shown in 1 H NMR.…”

Section: Resultsmentioning

confidence: 99%

⁹⁵Mo NMR: a useful tool for structural studies in solution

Brito

Teruel

Massou

et al. 2009

Magnetic Reson in Chemistry

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Oxomolybdenum(VI) complexes containing diverse ligands from an electronic and topological point of view have been analysed by means of (95)Mo NMR in solution with the purpose of using this technique as a tool to study their coordination chemistry and reactivity. The relationship between the electronic density on the metal tuned by the electron-donor ability of the coordinated ligands and the (95)Mo chemical shift has been proved for mono- and bimetallic complexes showing a hexa- or hepta-coordination around the metal centre. The different origins of the signal broadening (associated either to the symmetry of the metallic polyhedron or to the presence of isomers or to the ligand de-coordination) have been also considered to rationalise the obtained data.

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Applications of 95Mo NMR spectroscopy. XIII. Relaxation times of molybdenum compounds

Cited by 8 publications

References 15 publications

Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes

Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes

A 95Mo and 13C solid-state NMR and relativistic DFT investigation of mesitylenetricarbonylmolybdenum(0) – a typical transition metal piano-stool complex

⁹⁵Mo NMR: a useful tool for structural studies in solution

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Applications of 95Mo NMR spectroscopy. XIII. Relaxation times of molybdenum compounds

Cited by 8 publications

References 15 publications

Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes

Multinuclear NMR studies of molybdenum and tungsten carbonyl isocyanide complexes

A 95Mo and 13C solid-state NMR and relativistic DFT investigation of mesitylenetricarbonylmolybdenum(0) – a typical transition metal piano-stool complex

95Mo NMR: a useful tool for structural studies in solution

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⁹⁵Mo NMR: a useful tool for structural studies in solution