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Palladium Complexes with the Tridentate Dianionic Ligand Pyridine-2,6-dicarboxylate, dipic. Crystal Structure of
Pablo Espinet1, Jesús A. Miguel, Santiago García-Granda
1Departamento de Química Física y Analítica and Instituto Universitario de Química Organometálica "Enrique Moles"-Unidad asociada del CSIC, Universidad de Oviedo, 33071 Oviedo, Spain.
Abstract:
The reactions of [Pd(acac)(2)] or [Pd(OAc)(2)](3) with pyridine-2,6-dicarboxylic acid (H(2)dipic) in acetonitrile afford [Pd(dipic)(NCMe)] in high yield. This complex has been used as starting material in the preparation of a variety of neutral an anionic complexes. The dipicolinate anion behaves as a tridentate ligand in all cases, but two modes of coordination are found, depending on the ligand: as a pincer ligand O,N,O-bonded to the same palladium, giving mononuclear complexes, and as an O,N-chelate N,O'-bridging ligand in dinuclear complexes. An X-ray determination of the structure of a dimer, [Pd(dipic)(PBu(3))](2) (monoclinic, space group P2(1)/n, a = 18.144(4) Å, b = 13.191(2) Å, c = 19.571(3) Å, beta = 113.45(2) degrees, Z = 4, R = 0.050, R(w) = 0.054) shows that the ligand is coordinated to one palladium in a eta(2)-N,O chelate fashion and one oxygen atom of the other carboxylate group makes a bridge to the other palladium atom, in a novel bonding mode for the dipic ligand.