64741-28-2Relevant articles and documents
Ligand self-assembling through complementary hydrogen-bonding in the coordination sphere of a transition metal center: The 6- diphenylphosphanylpyridin-2(1H)-one system
Gellrich, Urs,Huang, Jing,Seiche, Wolfgang,Keller, Manfred,Meuwly, Markus,Breit, Bernhard
, p. 964 - 975 (2011/04/16)
Motivated by previous findings which had shown that transition metal catalysts based on the 6-diphenylphosphanylpyridone ligand (6-DPPon, 2) display properties as a self-assembling bidentate ligand-metal complex, we have performed a thorough study on the bonding situation of this ligand, alone and in the coordination sphere of a late transition metal. Thus, combining a number of spectroscopic methods (UV-vis, IR, NMR, X-ray), we gained insights into the unique structural characteristics of 2. These experimental studies were corroborated by DFT calculations, which were in all cases in good agreement with the experimental results. The free ligand 2 prefers to exist as the pyridone tautomer 2A and dimerizes to the pyridone-pyridone dimer 4A in solution as well as in the crystal state. The corresponding hydroxypyridine tautomer 2B is energetically slightly disfavored (ca. 0.9 kcal/mol within the up-conformer relevant for metal coordination); hence, hydrogen bond formation within the complex may easily compensate this small energy penalty. Coordination properties of 2 were studied in the coordination sphere of a platinum(II) center. As a model complex, [Cl2Pt(6-DPPon)2] (II) was prepared and investigated. All experimental and theoretical methods used prove the existence of a hydrogenbonding interligand network in solution as well as in the crystal state of 11 between one 6-DPPon ligand existing as the pyridone tautomer 2A and the other ligand occupying the complementary hydroxypyridine form 2B. Dynamic proton NMR allowed to determine the barrier for interligand hydrogen bond breaking and, in combination with theory, enabled us to determine the enthalpic stabilization through hydrogen-bonding to contribute 14-15 kcal/mol.
Hydrogen bonding as a construction element for bidentate donor ligands in homogeneous catalysis: Regioselective hydroformylation of terminal alkenes
Breit, Bernhard,Seiche, Wolfgang
, p. 6608 - 6609 (2007/10/03)
A new concept for the construction of bidentate ligands for homogeneous metal complex catalysis is described. The concept relies on the self-assembly of monodentate ligands through hydrogen bonding. As a prototype of such systems, 6-diphenylphosphanyl-2-pyridone (6-DPPon) was shown to form a chelate in the coordination sphere of a transition metal center through unusual pyridone/hydroxypyridine hydrogen bonding (X-ray). This hydrogen bonding stays intact in a catalytic reaction as proven upon highly regioselective hydroformylation of terminal alkenes. Regioselectivities and reactivities observed rank the 6-DPPon/rhodium system among the most active and regioselective catalysts for n-selective hydroformylation of terminal alkenes. Copyright
Synthesis, solid-state structures, and aggregation motifs of phosphines and phosphine oxides bearing one 2-pyridone ring
Akazome,Suzuki,Shimizu,Henmi,Ogura
, p. 6917 - 6921 (2007/10/03)
Three phosphines and their corresponding oxides bearing one 2-pyridone ring and two benzene rings were synthesized. Their single-crystal X-ray analyses exhibited three kinds of molecular aggregation: bimolecular aggregates, chiral one-dimensional structures, and achiral one-dimensional structures. In the bimolecular aggregate of (2-oxo-1,2-dihydro-x-pyridyl)diphenylphosphines (x = 3: 2a and 6: 2c), cyclic dimers that are derived from two 2-pyridone rings are observed. In contrast, (2-oxo-1,2-dihydro-5-pyridyl)diphenylphosphine (2b) molecules form a chiral one-dimensional chain via intermolecular hydrogen bonding. In the case of phosphine oxides, their oxygen always acts as a hydrogen acceptor of the hydrogen bonding. Thus, (2-oxo-1,2-dihydro-x-pyridyl)diphenylphosphine oxides (x = 3: 3a and 5: 3b) form hydrogen bonds intermolecularly between the oxygen atom on the phosphoryl group and the hydrogen atom on nitrogen to construct a chiral or an achiral one-dimensional chain. Interestingly, (2-oxo-1,2-dihydro-6-pyridyl)diphenylphosphine oxide (3c) exists as a 2-hydroxypyridine form (enol form) in a crystalline state, and intermolecular hydrogen bonds between the phosphoryl oxygen and the hydroxy proton construct an achiral one-dimensional chain.
