“…It was therefore decided to turn to model compounds that are not really structural models for the active sites, though all donor atoms are from the chalcogenides that are already binuclear (to avoid generation of the notorious M-O-M core), that are not too reactive (so that they are stable enough to survive several catalytic turnovers and last a reasonable time) and that contain the donor atoms of interest as -ether (-C-X-C-) or -one (-C=X) type function (to avoid redox reactions between ligand and metal; X = S, Se). [20][21][22][23] All used compounds were rather slow catalysts, but they were absolutely stable at catalytic conditions and processed 100 % of the lower concentrated substrate (PPh 3 ; DMSO was added in excess, see the catalytic procedure described above). For all used pairs of complexes, the studies showed that, despite nearly identical structural and electrochemical properties the catalytic activity was always different for sulfur-and selenium-based ligands, though for some complexes the Se compounds were better catalysts and for others it was vice versa.…”