title: Synthesis and properties of para-substituted NCN-pincer palladium and platinum complexes.
abstract: A variety of para-substituted NCN-pincer palladium(II) and platinum(II) complexes [MX(NCN-Z)] (M=Pd(II), Pt(II); X=Cl, Br, I; NCN-Z=[2,6-(CH(2)NMe(2))(2)C(6)H(2)-4-Z](-); Z=NO(2), COOH, SO(3)H, PO(OEt)(2), PO(OH)(OEt), PO(OH)(2), CH(2)OH, SMe, NH(2)) were synthesised by routes involving substitution reactions, either prior to or, notably, after metalation of the ligand. The solubility of the pincer complexes is dominated by the nature of the para substituent Z, which renders several complexes water-soluble. The influence of the para substituent on the electronic properties of the metal centre was studied by (195)Pt NMR spectroscopy and DFT calculations. Both the (195)Pt chemical shift and the calculated natural population charge on platinum correlate linearly with the sigma(p) Hammett substituent constants, and thus the electronic properties of predesigned pincer complexes can be predicted. The sigma(p) value for the para-PtI group itself was determined to be -1.18 in methanol and -0.72 in water/methanol (1/1). Complexes substituted with protic functional groups (CH(2)OH, COOH) exist as dimers in the solid state due to intermolecular hydrogen-bonding interactions.
authors.affiliation: Debye Institute, Department of Metal-Mediated Synthesis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Martijn Q
authors.initials: MQ
authors.lastname: Slagt
authors.forename: Gema
authors.initials: G
authors.lastname: Rodríguez
authors.forename: Michiel M P
authors.initials: MM
authors.lastname: Grutters
authors.forename: Robertus J M
authors.initials: RJ
authors.lastname: Klein Gebbink
authors.forename: Wim
authors.initials: W
authors.lastname: Klopper
authors.forename: Leonardus W
authors.initials: LW
authors.lastname: Jenneskens
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Spek
authors.forename: Gerard
authors.initials: G
authors.lastname: van Koten
mesh_terms: D006841:Hydrocarbons, Aromatic / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D015394:Molecular Structure; D009574:Nitro Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D009944:Organoplatinum Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*
chemical_list: D006841:Hydrocarbons, Aromatic; D008024:Ligands; D009574:Nitro Compounds; D009942:Organometallic Compounds; D009944:Organoplatinum Compounds; D010165:Palladium