title: Novel saccharinate-bridged palladium complexes for efficient C-O bond activation displaying promising luminescence properties.
abstract: The synthesis of mono- and dinuclear cyclometallated palladium(II) complexes with deprotonated saccharinate ligands displaying different coordination modes is described. The new compounds were prepared by direct reaction between saccharine and the corresponding hydroxo-complexes [{Pd(μ-OH)(C^N)}(2)] (C^N = 2-(2-pyridyl)phenyl (Phpy) I; = 7,8-benzoquinolyl (Bzq) II), showing a general formula [{Pd(μ-sac)(C^N)}(2)] with saccharinate 1 displaying a bridging -NCO-coordination mode. Bridge splitting with neutral ligands (L = pyridine (py) 2, quinoline (quinol) 3 or acridine (acrid) 4) yielded new mononuclear derivatives with saccharinate acting as an N-monodentated ligand. Structural characterization by X-ray diffraction of complexes I1, I2 and II2 confirmed the proposed formulae. All complexes emit in the solution and solid state at room temperature. Emission features between 640-680 nm in the solid state for complexes I1 and II1 are significantly red-shifted if compared to the emission in solution. These broad emissions are consistent with the simultaneous presence of (3)ππ* and (3)MMLCT transitions indicating the existence of a strong intramolecular Pd-Pd ground state interaction. The dimeric complexes have also shown to catalyze Suzuki-Miyaura cross-coupling of coumaryl tosylate and aryl boronic acids under phosphine-free conditions. Initial studies suggest the involvement of palladium nanoparticles, which has been further investigated using mercury-drop test and poisoning experiments.
authors.affiliation: Departamento de Química Inorgánica, Universidad de Murcia, Spain.
authors.forename: M Dolores
authors.initials: MD
authors.lastname: Santana
authors.forename: Rocío
authors.initials: R
authors.lastname: García-Bueno
authors.forename: Gabriel
authors.initials: G
authors.lastname: García
authors.forename: Gregorio
authors.initials: G
authors.lastname: Sánchez
authors.forename: Joaquín
authors.initials: J
authors.lastname: García
authors.forename: Anant R
authors.initials: AR
authors.lastname: Kapdi
authors.forename: Minal
authors.initials: M
authors.lastname: Naik
authors.forename: Suhas
authors.initials: S
authors.lastname: Pednekar
authors.forename: José
authors.initials: J
authors.lastname: Pérez
authors.forename: Luis
authors.initials: L
authors.lastname: García
authors.forename: Eduardo
authors.initials: E
authors.lastname: Pérez
authors.forename: J Luis
authors.initials: JL
authors.lastname: Serrano
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D008024:Ligands; D049408:Luminescent Agents / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009942:Organometallic Compounds / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry
chemical_list: D008024:Ligands; D049408:Luminescent Agents; D009942:Organometallic Compounds; D011725:Pyridines; D010165:Palladium; D002244:Carbon; C023666:pyridine; D010100:Oxygen