Structure and stability of various (C2H5Ge)+ ions. An ab initio molecular orbital study

Various (C2,Hs,Ge)+ stable isomers have been identified on the corresponding SCF 3-21G* potential energy surface. Twelve distinct structures have been characterized, and their relative stability has been evaluated at the correlated MP2 and QCISD(T) post-SCF levels of theory, with double-{quality basis sets. Several analogies do exist with the previously described (C3,Hs)+ species, although significant differences can be pointed out. Distinct stable species have been found in correspondence of allyl-like, 2-propenyl-like, and 1 -propenyl-like (C2,Hs,Ge)+ structures (ions 1,2,6,7-9, and 1&12), and the mechanisms of stereomutation of the allyl-like ions, via transition structures 3-5, have been examined. Whereas the allyl cation is by far the most stable among the (C~,HS)i+so mers, the germylene-like species 10, which contains low-coordinated germanium atoms, has been computed as the most stable among the (C2,Hs,Ge)+ investigated ions.