Coordination shifts in carbon-13 spectra of olefin and arene metal complexes

Enol radical cations in solution. Part 12. Synthesis and electrochemical investigations of a stable enol linked to a ferrocene redox centre †

“…ether. Drying (Na 2 SO 4 ), removal of the solvent in vacuo and column chromatography (cyclohexane-dichloromethane, 3 : 1) of the remaining crude product yielded the desired pure benzofuran 4 as an orange solid (9.0 mg, 19 The dimesityl ketone was characterised on the basis of its spectral data such as 1 H NMR, 21 13 C NMR, 22 MS and IR. 23 General procedure for the one-electron oxidation of the enol 3 or the enolate 6 with various amounts of Fephen Under nitrogen, enol 3 and the appropriate amount of Fephen were weighed in two different flasks and CH 3 CN (each 3.0 cm 3 ) was added.…”

A 13C‐NMR. Study of naphthalene chromium complexes. Correlation with reactivity: Nucleophilic aromatic substitution reactions

“…Coordination of an arene to a transition metal causes large shifts to lower frequencies of the ring C-resonances in respect to the free arene [15]. The increase in shielding has been variously attributed to metal ligand bond anisotropy [ 16-181, changes in ring C-hybridization [19] and changes in electron density in the 0- [20] [21] and n- [22- interpretation of these shifts is not yet available [26] [27], however, a thorough study of the factors that influence the coordination shift concludes that changes in n-electron density and, particularly, metal to arene n*-backbonding play a dominant role in the observed shielding of coordinated arenes [23]. These conclusions receive support from the results of molecular orbital calculations [25] [28-301 and a He (I) photoelectron study [3 11.…”

Dichlorobis(pyridine)zinc(II) – a redetermination

“…1,3,3,5-TETRA METHY L -6-( 1 ', 2'-N A P H TH O) -BICYCLO[3,2,1 ] O CTENE sky, Kowalski & Avery, 1974;Thoennes, Wilkins & Trahanovsky, 1974). For example, the C(19) methyl proton n.m.r, shift data are, respectively, 6.=-0.38 and 3n=-0.08 [3(TMS)=0.00] for C20H24 and C23H24OaCr, indicating markedly increased proton shielding in the former.…”