Interaction of palladium(II) acetate with substituted pyridines, including a cyclometallation reaction and the structure of [Pd{meso-[(py)PhMeC]2C5H3N}(O2CMe)][O2CMe]·3H2O

Abstract

The reactivity of meso- and rac- diastereoisomers of 2,6-bis[1-phenyl-1-(pyridin-2-yl)ethyl]pyridine {[(py)PhMeC]₂C₅H₃N}, 2,6-bis[1,1-bis(pyridin-2-yl)ethyl]pyridine {[(py)₂MeC]₂C₅H₃N}, and the pyridin-2-yl methanes (py)_nPh_3–nCH (n= 1–3), (py)_nCH_4–n(n= 2 or 3), and (py)₃PhC toward palladium(II) acetate in refluxing glacial acetic acid and at ambient temperature in organic solvents has been investigated. The nitrogen donor ligands form co-ordination derivatives in organic solvents. All except α-phenyl-α-(pyridin-2-yl)toluene[(py)Ph₂CH] form identical complexes in glacial acetic acid, with (py)Ph₂CH undergoing cyclometallation to form [{Pd[(py)PhHCC₆H₄](µ-O₂CMe)}₂]. meso-[(py)PhMeC]₂C₅H₃N, which binds as a tripodal tridentate ligand to methylmercury(II), has been shown by a single crystal X-ray study to act as a planar tridentate ligand to palladium(II) in [Pd{meso-[(py)PhMeC]₂C₅H₃N}(O₂CMe)][O₂CMe]·3H₂O with square-planar co-ordination being completed by a unidentate acetate group [monoclinic, space group P2₁/c, a= 11.795(5), b= 23.10(1), c= 12.313(5)Å, β= 95.64(3)°, Z= 4; R= 0.051 for 3 657 ‘observed’ reflections]. Syntheses of the new ligand [(py)₂MeC]₂C₅H₃N, with five pyridine donor groups, and α,α,α-tris(pyridin-2-yl)toluene [(py)₃PhC] are described.