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Alkylcyclopentanes
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
Both preparative routes take advantage of the extraordinarily high acidity of simple cyclopentadienes. The very low pKa of cyclopentadiene (pKa = 18) compared to that of other simple hydrocarbons (pKa = 30 or greater) arises from the aromaticity of the cyclic six-electron periphery of the cyclopentadienide anion, Equation 17.2.
Reactivity of a β-diketiminate ytterbium(II) hydride with cyclopentadiene derivatives
Published in Journal of Coordination Chemistry, 2022
Georgia M. Richardson, Jesse Howarth, Matthew J. Evans, Alison J. Edwards, Scott A. Cameron, Mathew David Anker
We have demonstrated that the β-diketiminate ytterbium(II) hydride [(BDIDipp)Yb(H)]2 can react with a range of substituted cyclopentadienes to provide mononuclear heteroleptic ytterbium(II) cyclopentadienyls with extrusion of hydrogen gas. The tetramethyl- and pentamethyl-cyclopentadienyl, indenyl and fluorenyl compounds were structurally characterized by single crystal X-ray diffraction, with solid state data confirming the retention of the oxidation state on the ytterbium(II) center. Each cyclopentadienide complex contains close interactions between the cyclopentadienyl ligand and the ytterbium center. For the pentamethylcyclopentadienyl derivative, an Yb···η3-H2C agostic interaction was characterized using single crystal neutron diffraction, along with an additional Yb···H interaction. In solution, each cyclopentadienide complex was structurally elucidated, with broad signals observed for the sterically congested indenyl and fluorenyl derivatives. The results from this contribution provide a means to install a cyclopentadienyl ligand into a lanthanide(II) complex from the corresponding cyclopentadiene reagents.
Field-cycling long-lived-state NMR of 15N2 spin pairs
Published in Molecular Physics, 2018
Stuart J. Elliott, Pavel Kadeřávek, Lynda J. Brown, Mohamed Sabba, Stefan Glöggler, Daniel J. O'Leary, Richard C. D. Brown, Fabien Ferrage, Malcolm H. Levitt
In this paper we present a 15N labelled molecular structure (Figure 1) exhibiting a long-lived state lifetime exceeding 40 minutes in solution. This system (15N-I) is constructed by a Diels-Alder reaction of (S)-4-(1-phenylethyl)-3H-1,2,4-triazole-3,5(4H)-dione-1,2-15N and a fully deuterated cyclopentadiene. Although the spin-lattice and long-lived state relaxation times are relatively short at high field, impressive relaxation times are unveiled at low field. The decay of the long-lived state is biexponential, with the slowly relaxing component having a time constant ∼21 times longer than . Experiments at low field make use of a dedicated two-field NMR spectrometer which allows fast transfer of a sample shuttle between two magnetic field centres operating at different magnetic fields (14.1 T and 0.33 T), and with radiofrequency irradiation at low magnetic field. The dipolar relaxation mechanisms of the long-lived state are discussed.
A TDDFT study of some dinuclear compounds containing CpM(CO)3 or CpM(CO)2 groups
Published in Molecular Physics, 2020
Metal carbonyls containing metal–metal bonds and cyclopentadiene as a ligand (Cp hereafter) are known so far. Their electronic spectroscopy and photochemistry had been studied during the seventies [1–4]. Some of them have interesting properties. For instance, the photolysis of with single metal–metal bonds leads to heterodinuclear compounds, or also different compounds with loss of carbonyls [4,5]. Other compounds, such as Cp(CO)2M≡M(CO)2Cp (M=Cr, Mo, W), are supposed to have a triple bond, and their reaction with small molecules can lead to the addition of this molecules to the triple bond [6–8].