Intramolecular Nonbonded Interactions Between Divalent Selenium Centers with Donor and Acceptor Substituents

Abstract

Abstract To investigate the intramolecular van der Waals interactions between two divalent selenium centers in the solid state and in solution, we have prepared methyl 2‐(methylselenyl)benzyl selenide ( 1 ), ethynyl 2‐(methylselenyl)benzyl selenide ( 2 ), and 2‐(methylselenyl)benzyl selenocyanate ( 3 ). By means of NMR spectroscopic studies we have determined the 77 Se NMR chemical shifts of the signals of the Se centers of 1 – 3 and their long‐range 4 J Se,Se coupling constants. These results, and the X‐ray structural studies of single crystals of 3 and 11 , a quasi‐dimer of 2 , point to an Se ··· Se van der Waals interaction and short Se ··· H distances in 1 – 3 . These measurements were supported by quantum chemical calculations on 1 – 3 at the MP2/6‐311+g(d)//B98/6‐311+g(d) level of theory, which showed a preference for the endo X and endo H conformations of 1 – 3 . This finding was confirmed by calculations of the 77 Se NMR chemical shifts of 1 – 3 by GIAO‐B98 and GIAO‐PBE calculations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)