RPA MNDO ANALYSIS OF THE DIHEDRAL ANGLE DEPENDENCE OF VICINAL J(SNSN)AND J(SNC) NMR COUPLING-CONSTANTS

Vicinal J(SnCCSn) and J(SnCCC) spin-spin coupling constants are calcul ated within the RPA MNDO method for different dihedral angles, theta, determined by the intervening bonds, in model compounds. For both type s of couplings, calculated values closely follow Karplus-like dependen ces. Results are discussed in terms of experimental values, and the ef fects of substituents attached to the coupled atoms are briefly analyz ed for the theta = 0 degrees and theta = 180 degrees conformations. Th ese last values were also calculated using the RPA AM1 method. Results indicate that the RPA MNDO and RPA AM1 approaches show interesting po tential for studying the structural dependences of (3)J(SnSn) and (3)J (SnC) couplings in tin-containing compounds.