4026-05-5Relevant articles and documents
Dinuclear cobalt complexes with a redox active biphenyl bridging ligand [Co2(BP)(tqa)2](PF6)2(H4BP = 4,4′-bis(3-tert-butyl-1,2-catechol), tqa = tris(2-quinolylmethyl)amine): structure and magnetic properties
Kuroda-Sowa, Takayoshi,Maekawa, Masahiko,Mibu, Takuto,Okubo, Takashi,Suenaga, Yusaku,Sugimoto, Kunihisa
, p. 9833 - 9841 (2021/07/28)
The biscatechol, H4BP (4,4′-bis(3-tert-butyl-1,2-catechol)) that can directly connect two redox active catechol moieties was synthesized. Also, tris(2-pyridylmethyl)amine (tpa), bis(2-pyridylmethyl)(2-quinolylmethyl)amine (bpqa), (2-pyridylmethyl)bis(2-quinolyl methyl)amine (pbqa), and tris (2-quinolylmethyl)amine (tqa) were synthesized as terminal ligands of the tetracoordinated tripod. In total, five different dinuclear Co complexes were synthesized from H4BP with various terminal ligands as follows, [Co2(BP)(tpa)2](PF6)2(1), [Co2(BP)(tpa)2](PF6)3(2), [Co2(BP)(bpqa)2](PF6)2(3), [Co2(BP)(pbqa)2](PF6)2(4), and [Co2(BP)(tqa)2](PF6)2(5). After a one-electron oxidation reaction of complex (1), complex (2), was isolated as a mixed valence state lsCoIII-[SQ-Cat]-lsCoIII, with an absorption intensity of about 1370 nm (intervalence charge transfer (IVCT) bands) in CH3CN solution. In addition, an investigation of the magnetic properties of the dinuclear Co complex (3) with SQUID showed that theχMTvalue gradually increased as the temperature increased from 280 to 380 K. Studies in the solid and solution states using electronic spectra, cyclic voltammetry and SQUID for the above complexes provide clear evidence for three different charge distributions: complexes (1) and (3) are CoIII-[Cat-Cat]-CoIII, complex (2) is CoIII-[Sq-Cat]-CoIII, complexes (4) and (5) are CoII-[Sq-Sq]-CoII. Of the five cobalt dinuclear complexes, only complex (3) shows evidence of the temperature dependence of the charge distribution, displaying a thermally induced valence tautomeric transition from the lsCoIII-[Cat-Cat]-lsCoIIIto hsCoII-[Sq-Sq]-hsCoIIin both solid and solution states. However, this valence tautomeric step is incomplete at 380 K, with the?χMT?value of hsCoII-[Sq-Sq]-hsCoII. This suggests that the steric hindrance of the quinolyl rings around the Co ion produces a coordination atmosphere that is weaker than that observed with pyridyl rings, which facilitates a change in the CoIIIions to CoII
Synthesis and use of ortho-(branched alkoxy)-tert-butoxybenzenes
Rast, Slavko,Stephan, Michel,Mohar, Barbara
supporting information, p. 6815 - 6818 (2013/01/15)
A series of sterically hindered o-(branched alkoxy)-tert-butoxybenzenes was efficiently prepared in good yields owing to a new practical and simple preparation of o-tert-butoxyphenol starting from catechol and isobutene. Use of DMF di-tert-butyl acetal reagent instead of isobutene/H2SO 4 (cat.) for O-tert-butylation was very convenient in case of ortho bulky phenols affording the corresponding tert-butyl ethers in high yield and purity. This general route proved to be useful since no reliable access was available to o-di-t-BuO-substituted arenes. Application to the synthesis of congested phosphorus-based compounds is presented.
Alkylation of pyrocatechol in tert-butyl alcohol-sulfuric acid-benzene
Vol'eva,Prokof'eva,Belostotskaya,Komissarova,Gorbunov,Kurkovskaya
body text, p. 1310 - 1312 (2011/12/05)
Alkylation of pyrocatechol with tert-butyl alcohol in benzene in the presence of sulfuric acid gave 3,5-di-tert-butylbenzene-1,2-diol in a higher yield than in analogous reaction with tert-butyl alcohol. This result was rationalized by reduction of inhibitory effect of liberated water, formation of heterogeneous system, and occurrence of the alkylation process in nonpolar organic phase. Intermediate products were identified and found to undergo intra- and intermolecular tert-butyl group transfer with formation of more stable 3,5-di-tert-butylbenzene-1,2-diol. The formation of p-di-tert-butylbenzene indicated participation of benzene in crossalkylation processes. Pleiades Publishing, Ltd., 2011.
