Barriers to rotation of the cyclopentadienyl ligand: spin-lattice relaxation time measurements and atom–atom potential calculations on cyclopentadienyl manganese and rhenium tricarbonyl and vanadium tetracarbonyl complexes

Gilson, D. F. R.; Gomez, G.; Butler, Ian S.; Fitzpatrick, Paul J.

doi:10.1139/v83-137

Cited by 30 publications

(15 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The barrier to rotation in solid 157 was studied by both quasi-elastic neutron scattering (QENS) 671 and spin-lattice relaxation NMR measurements. 672 QENS gave a value of 4.0 kcal mol -1 , which would appear to be high for this relatively unhindered molecule, and NMR T 1 measurements provided a more likely value of 1.7 kcal mol -1 (∆G q ). A larger than expected value was also obtained for 158 (4.9 kcal mol -1 ) 673 using mechanical spectroscopy.…”

Section: Piano-stool (Half-sandwich) Transition Metal Complexes and Rmentioning

confidence: 86%

“…A larger than expected value was also obtained for 158 (4.9 kcal mol -1 ) 673 using mechanical spectroscopy. 674 Similarly, Gilson et al 672 measured the barriers to rotation in 159 and 160 by spin-lattice relaxation NMR and found similar values (∆G q ) of 1.71 and 1.70 kcal mol -1 , respectively. Earlier, they had measured the barrier in 161 and found it to be a seemingly high 2.3 kcal mol -1 , which is the upper limit measured for ferrocene.…”

Section: Piano-stool (Half-sandwich) Transition Metal Complexes and Rmentioning

confidence: 91%

See 1 more Smart Citation

Artificial Molecular Rotors

et al. 2005

View full text Add to dashboard Cite

Section: Piano-stool (Half-sandwich) Transition Metal Complexes and Rmentioning

confidence: 86%

Section: Piano-stool (Half-sandwich) Transition Metal Complexes and Rmentioning

confidence: 91%

Artificial Molecular Rotors

et al. 2005

View full text Add to dashboard Cite

“…[5] Linewidth, second moment and spin-lattice relaxation times have been extensively used for the evaluation of rotational barriers. [39][40][41][42] The greater molecular symmetry involved in Cp and arene systems π-bonded to the metal permits the ring to undergo jumps between equivalent potential energy minima. One may envisage that when the ligand shape is regular and symmetric, smaller barrier between complementary geometries are expected.…”

Section: -Arenementioning

confidence: 99%

Solid‐State NMR Investigation of Ligand Mobility and Reactivity in Transition Metal Complexes

Chierotti

Gobetto

2009

Eur J Inorg Chem

View full text Add to dashboard Cite

Solid-state NMR spectroscopy represents a powerful tool to access information on chemical structure, dynamics and reactivity at molecular level on solid compounds and materials. Transition metal complexes represent an unrestricted source of examples for solid-state dynamics and reactivity due to the presence of highly mobile groups, very reactive ligands and the possibility of expanding the coordination sphere. The key question of the influence of the mobility on the reactivity of a system is the occasion for presenting several selected examples of solid-state dynamics and reactivity of transition metal complexes. Although only few unambiguous examples

show abstract

“…the cyclobutadienyl ring in ( Q~-C~H~) F~( C O )~I~ and the cyclopentadienyl ring in various derivatives such as (qS-CSHs)Mn(C0)3. [17][18][19] The principal approaches have been to study the temperature dependence of the proton spin-lattice relaxation times and to perform nonbonded atom-atom potential calculations. The calculations have provided useful information on the origin and magnitude of the various contributions to the rotational b a r r i e r~, l~,~~ which are directly dependent on the packing and the sites occupied by the molecules in the unit cell.…”

Section: Introductionmentioning

confidence: 99%

Spectral study of tris(.beta.-dionato)cobalt(III) chelates. Structure-redox potential relations

Tsiamis¹,

Cambanis²,

Hadjikostas³

1987

Inorg. Chem.

View full text Add to dashboard Cite

intensity of the main line) and is lost in the base line. If a hidden higher binding energy peak were comparable in intensity to that of the lower binding energy peak, then the Ru 3d512 intensity derived from the deconvoluted spectrum shown in Figure 1 would be anomalously low compared with that of other complexes while the C 1s line intensity would be anomalously high. Furthermore, the large Ru 3d splitting required to hide the high-binding-energy Ru 3d peak under the C 1s line ought to be observable even in the Ru 2p3/2 spectrum of the complex. We examined these possibilities by comparing Ru 3d5/2/C1 2p and Ru 2p312/CI 2p intensity ratios recorded for 7 with those of all the other ruthenium chloride complexes. The Ru 3d5/?/C1 2p and Ru 2~~,~/ C l 2p intensity ratios for 7 are both within 20% (albeit on the low side of all but one) of all other measured ratios. The Ru 2p3p line width for 7 is normal. Given experimental errors, we find then that at least 80% of the Ru 3d512 intensity expected from two ruthenium centers in 7 is accounted for in the deconvoluted spectrum. Consequently, the metal XP spectrum of 7 is consistent with that of a strongly delocalized class I11 complex. For such a complex a large portion of the total metal core level photoemission intensity resides in a single, low-binding-energy line. From the quality of the spectrum we estimate, using eq 2, that the electron exchange parameter a for 7 must be greater than 0.9. ConclusionsThe diruthenium complexes examined have provided the opportunity to systematically assess the effects of ligand coordination environment, metal oxidation state, and metal-metal interaction on the metal XP spectra. One complex is of particular interest in this series; the symmetric, mixed-valence [Ru(II),Ru(III)] complex [As(p-tol)3]2C1RuC13RuC1[As(p-tol)3]2. Depending onthe strength of the metal-metal interaction, the metal XP spectrum from this complex could give any results along the continuum from two equally intense metal lines separated by 1 eV or more, to unequal intensities from the two lines with the lower binding energy line "stealing" intensity from the higher binding energy line, to a single, narrow metal line (indistinguishable metal centers). The spectrum observed is a function of the extent of unpaired electron delocalization during photoemission. It was found that, to the degree of resolution possible, this complex gives a metal spectrum in which at least 80% of the metal signal is present in a single, low-binding-energy final state. This experimental result reflects more extensive unpaired electron delocalization in this complex compared with that in the Creutz-Taube complex [(NH3)5Ru(pz)Ru(NH3)5]5+, which gives two well-separated metal lines of equal intensity. We estimate the value of a in 7 is greater than 0.9, whereas in the Creutz-Taube complex it is less than 0.10. This work, combined with Hush's theory, suggests that very unusual metal XP spectra ought to be obtained from class I11 mixed-valence complexes having metal-metal spacings between 3.5 an...

show abstract

Barriers to rotation of the cyclopentadienyl ligand: spin-lattice relaxation time measurements and atom–atom potential calculations on cyclopentadienyl manganese and rhenium tricarbonyl and vanadium tetracarbonyl complexes

Cited by 30 publications

References 11 publications

Artificial Molecular Rotors

Artificial Molecular Rotors

Solid‐State NMR Investigation of Ligand Mobility and Reactivity in Transition Metal Complexes

Spectral study of tris(.beta.-dionato)cobalt(III) chelates. Structure-redox potential relations

Contact Info

Product

Resources

About