1-cyclohepta-2,4,6-trienyl-selanes - a Se-77 NMR study: Indirect nuclear Se-77-C-13 spin-spin coupling constants and application of density functional theory (DFT) calculations

摘要

1-Cyclohepta-2,4,6-trienyl-selanes Se(C7H7)(2) (2c), R-Se-C7H7 with R = Bu, Bu-t, Ph, 4-F-C6H4 (12a,b,c,d) were prepared by the reaction of the corresponding silanes, Si(SeMe3)(2) and R-Se-SiMe3, respectively, with tropylium bromide C7H7Br. In spite of the low stability of the selanes even in dilute solutions and at low temperature, they could be characterised by their H-1, C-13 and Se-77 NMR parameters. Coupling constants (1)J(Se-77,C-13) were measured and calculated by DFT methods at the B3LYP/6-311+G(d,p) level of theory. The comparison of experimental and calculated coupling constants (1)J(Se-77, C-13) included numerous selenium carbon compounds with largely different Se-C bonds, revealing a satisfactory agreement. Both the spin-dipole (SD) and the paramagnetic spin-orbital (PSO) terms contributed significantly to the spin-spin coupling interaction, in addition to the Fermi contact (FC) term. Copyright (C) 2006 John Wiley & Sons, Ltd.