Experimental and quantum chemical investigation of the stereochemical dependence of spin coupling constants in symmetrical strained alkenes

The C-13-C-13, C-13-H-1 and H-1-H-1 spin coupling constants in some straine d symmetrical alkenes were measured using a new gradient selected method. T he olefinic (1)J(C,C) spin coupling constants were calculated using ab init io and DFT quantum chemical calculations for model compounds. The calculate d and experimental data are: in good agreement. The olefinic (1)J(C,C) spin coupling constants do not reflect the high distortion of the double bond i n silacycloheptene 2. This is attributed to the fact that the Fermi contact contribution to the coupling constants is transmitted via the sp(2)-type s igma-orbital, whereas the pi-type MO with a nodal plane at the position of the nuclei does not contribute to the C-13-C-13 coupling. Copyright (C) 200 0 John Wiley & Sons, Ltd.