Primary vinylic and acetylenic germanes and stannanes, synthesized by a chemoselective reduction of the corresponding trichloro derivatives, were investigated by ab initio quantum chemical methods and photoelectron spectroscopy. In particular, the PE spectra display very well-resolved bands which show the increasing destabilizing effect of 14 group heteroatom cl-substitution of double or triple carbon-carbon bonds. (C) 1998 Elsevier Science S.A. All rights reserved.