Chromium tricarbonyl complexes of 1,2-and 1,4-dihydronaphthalene. Synthesis and metal-induced thermal isomerizations involving endo-hydrogen atomsстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Reaction of 1,4-dihydronaphthalene with (NH3)3Cr(CO)3 for 2 h in dioxane at 100˚С or with Py3Cr(CO)3 for 1h at –30˚С in ether in the presence of BF3.Et2O gives mixture of (6-dihydronaphthalene)chromium tricarbonyl complexes 1 и 2 with the yields 45 и 50% and the ratios [1/2] = 63:37 and 55:45, correspondingly. Complexes 1 and 2 were separated chromatographically.
Thermal reversible rearrangement of chromium tricarbonyl complexes of 1,2- and 1,4-dihydronaphthalene 1 2 proceeds in different solvents at 130oC and was experimentally investigated in deuterated species by means of 2D NMR spectroscopy. Analysis of 2D NMR spectra shows that isomerization proceeds via metal induced 1,5-endo-hydrogen shifts. Isomerization mechanism was examined with the use of quantum chemistry calculations in the frame of density function theory (DFT). Process goes with highest activation barrier 33.2 kcal/mol via number of agostic and hydride intermediates and transition states in which chromium metal atom stereospecifically activates only endo-hydrogen atoms.