Stereochemical behavior of 77Se‐1H spin‐spin coupling constants in pyrazolyl‐1,3‐diselenanes and 1,2‐diselenolane

Conformational study of five derivatives of 2-(pyrazol-4-yl)-1,3-diselenane together with related 1,2-diselenolane in respect to the stereochemical trends of geminal and vicinal (77)Se-(1)H spin-spin coupling constants has been carried out by means of high-level theoretical calculations in combination with experiment. The marked dihedral angle dependences for both types of couplings accounted for the lone pair effect in the case of geminal coupling constants and the Karplus-type relationship for vicinal couplings have been established, which is of major importance for the stereochemical analysis of saturated selenium containing heterocycles.