The review is focused on five-coordinate Pd(II)- and Pt(II)-alkene com
plexes with a trigonal bipyramidal arrangement of the ligands. Synthet
ic methods are extensively described and the characterization procedur
es of 243 compounds are listed. Stereochemical and reactivity aspects
are reported. A chart with the X-ray structural parameters of 19 compl
exes and a list of 76 references are included.