The use of bidentate ligands in the directed Pauson-Khand reaction was investigated. Substrates with a three-carbon linkage between the two heteroatoms gave better results than substrates containing two-carbon tethers. Higher yields and better regioselectivities were observed with thioamines and bisthioethere compared to diamines. Overall, only a few bidentate substrates showed marked improvementa over previous results obtained with ...