Tetradentate selenium ligand as a building block for homodinuclear complexes of Pd(ii) and Ru(ii) having seven membered rings or bis-pincer coordination mode: high catalytic activity of Pd-complexes for Heck reaction
coordination mode. The geometry around Pd in 1 or 2 is close to square planar whereas in 3, Ru has pseudo-octahedral half sandwich “Piano–Stool” geometry. The Pd–Se bond distances are in the ranges 2.4004(9)–2.4627(14) Å and follow the order 1 > 2, whereas Ru–Se bondlengths are between 2.4945(16) and 2.5157(17) Å. The 1 and 2 have been found efficient catalysts for Heck reaction of aryl halides with styrene