So far, in addition to halogen atoms, other non-metallic atoms can become part of the aromatic heterocycle, and the target ring system is still aromatic.Havlin, Robert; McMahon, Michael; Srinivasan, Ranjani; Le, Hongbiao; Oldfield, Eric researched the compound: Chloro(1,5-cyclooctadiene)copper(I) dimer( cas:32717-95-6 ).COA of Formula: C16H16Cl2Cu2.They published the article 《Solid-State NMR and Density Functional Investigation of Carbon-13 Shielding Tensors in Metal-Olefin Complexes》 about this compound( cas:32717-95-6 ) in Journal of Physical Chemistry A. Keywords: carbon 13 shielding metal olefin complex; NMR carbon 13 shielding olefin complex; density functional NMR carbon 13 shielding. We’ll tell you more about this compound (cas:32717-95-6).
The authors determined the principal elements of the chem. shift tensors for metal-olefin complexes: [Ag(cod)2]BF4 (cod = cis,cis-cycloocta-1,5-diene), [CuCl(cod)]2, PtCl2(cod), [RhCl(cod)]2, and K[PtCl3(C2H4)] using magic-angle sample spinning and a Bayesian probability method to deduce μ, ρ in the Herzfeld-Berger equations. These principal elements also were computed by using d. functional methods with two different types of functionals and partial geometry optimization. The overall slope and R2 values between the theor. and exptl. tensor elements are good, ranging from 1.06 to 1.16 for the slope (vs. the ideal value of 1) and 0.98-0.99 for the goodness of fit parameter R2 (vs. the ideal value of 1). The use of a hybrid functional results in a slightly worse slope, an effect which is largest for the compounds with the largest paramagnetic shifts. There are no particularly good correlations between C-C bond lengths, isotropic/anisotropic shift tensor elements or computed bond orders; however, the correlation between shielding and (Mulliken) charge of ∼-120 ppm/electron is consistent with previous exptl. estimates on olefins and aromatic compounds The orientations of the shielding tensor elements in the cod complexes change in a relatively continuous manner with increases in shielding (from d10 to d8 metals), with δ33 becoming highly rotated (37.5°) from the normal to the C:C bond axis in [RhCl(cod)]2. Overall, these results indicate that d. functional methods now permit the relatively accurate reproduction of metal-ligand shielding patterns in systems whose structures are known, which should facilitate their use in probing metal-ligand geometries in systems whose structures are less certain, such as in metalloproteins.
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Reference:
Quinoxaline – Wikipedia,
Quinoxaline | C8H6N2 | ChemSpider