Bis-alkene Complexes of Stannylium and Germylium Ions

Bis-alkene complexes of triorgano-substituted cations of stannylium and germylium ions were synthesized by alkyl fragmentation reactions and were characterized by NMR spectroscopy and for the tin compound also by X-ray structure analysis of the corresponding perfluorinated tetraarylborate. According to experimental results and quantum mechanical computations, the central group 14 element adopts in these pentacoordinated cations a distorted trigonal-bipyramidal coordination geometry with the two CC double bonds occupying the apical positions. This geometrical arrangement places seven carbon atoms at a distance less than the sum of the van der Waals radii around the central atom. Quantum mechanical computations at the MP2/6-311G(d,p) (C,H) SDD (Sn, Ge, Si) level reveal substantial interaction energies between the group 14 element and the CC double bond and electron density distributions that are typical for noncovalent π-donor interactions.