title: Hydroxy- and mercaptopyridine pincer platinum and palladium complexes generated by silver-free halide abstraction.
abstract: A silver-free route has been employed for the synthesis of a number of Pd and Pt complexes supported by an NCN "pincer" ligand (NCN = [2,6-(Me2NCH2)2C6H3]-) via halide abstraction. This was achieved by the use of o-, m-, and p-hydroxypyridines or o- and p-mercaptopyridines in basic ethanol solutions. The acidic OH or SH protons are removed to generate the formally anionic ligands. X-ray crystal structure determination of these complexes shows that the bonding of the substituted pyridine ligands occurs exclusively through the pyridine N for hydroxypyridines and exclusively through the thiol S in mercaptopyridines. In the hydroxypyridine case, the ortho and para isomers tautomerize to generate pyridone structures with a covalent M-N bond, whereas the m-hydroxypyridine complex, which is unable to tautomerize, is found to still be bound through the pyridine N but in a zwitterionic structure. The mercaptopyridine complexes are the first reported examples of pincer-ligated Pd and Pt thiolate species. The pyridine ligands can be quantitatively exchanged for chloride by reaction with excess NH4Cl, a potentially useful chemical switch for ligation/decomplexation of this ligand type.
authors.affiliation: Debye Institute, Organic Chemistry and Catalysis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
authors.forename: Alexey V
authors.initials: AV
authors.lastname: Chuchuryukin
authors.forename: Preston A
authors.initials: PA
authors.lastname: Chase
authors.forename: Allison M
authors.initials: AM
authors.lastname: Mills
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Spek
authors.forename: Gerard P M
authors.initials: GP
authors.lastname: van Klink
authors.forename: Gerard
authors.initials: G
authors.lastname: van Koten
mesh_terms: D015392:Chemistry, Inorganic / Q000379:methods*; D018360:Crystallography, X-Ray; D008024:Ligands; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry; D010984:Platinum / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry / Q000378:metabolism; D012834:Silver / Q000737:chemistry
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D012834:Silver; D010984:Platinum; D010165:Palladium; C029347:2-thiopyridine