219837-63-5Relevant academic research and scientific papers
Synthesis and Characterization of Palladium(II) Complexes with New Polydentate Nitrogen Ligands. Dynamic Behavior Involving Pd-N Bond Rupture. X-ray Molecular Structure of [{Pd(η3-C4H7)} 2(Me-BPzTO)](4-MeC6H4SO3) [Me-BPzTO = 4,6-Bis(4-methylpyrazol-1-yl)-1,3,5-triazin-2-olate]
Torre, Felipe Gómez-De La,De La Hoz, Antonio,Jalón, Félix A.,Manzano, Blanca R.,Otero, Antonio,Rodríguez, Ana M.,Rodríguez-Pérez, M. Carmen,Echevarría, Aurea,Elguero, José
, p. 6606 - 6614 (1998)
The ligands 2,4,6-tris(4-methylpyrazol-1-yl)-1,3,5-triazine (Me-TPzT), 2,4,6-tris(4-bromopyrazol-1-yl)-1,3,5-triazine (Br-TPzT), and 2-methoxy-4,6-bis(4-methylpyrazol-1-yl)-1,3,5-triazine (Me-BPzTOMe) have been synthesized and their reactions with some palladium derivatives explored. The palladium fragment [Pd(η3-2-Me-C3H4)(S)2] +, S = acetone, reacts in acetone with Me-TPzT or Br-TPzT in a 3:1 molar ratio to generate new complexes in which two allylpalladium fragments are present and the TPzT ligands have been partially hydrolyzed: [{Pd(η3-C4H7)}2(X-BPzTO)]A, X-BPzTO = 4,6-bis[4-methyl(or bromo)pyrazol-1-yl]-1,3,5-triazin-2-olate (X = Me, A = BF4, 1; A = PF6, 2; A = CF3SO3, 3; A = p-MeC6H4SO3, 4; X = Br, A = CF3SO3, 5). When the ligand Me-BPzTOMe is made to react with only 1 equiv of the palladium solvate, compound 6, [Pd(η3-2-Me-C3H4)(Me-BPzTOMe)]CF 3SO3, is isolated. Reaction of 6 with another 1 equiv of the palladium derivative leads to 3. The intermediate 7, [{Pd(η3-2-Me-C3H4)} 2(Me-BPzTOMe)]CF3SO3, has been isolated as an almost pure compound. The reaction of Me-BPzTOMe with 1 equiv of [Pd(C6F5)2(cod)] (cod = 1,5-cyclooctadiene) leads to the complex [Pd((C6F5)2(Me-BPzTOMe)], 8. Attention has been focused on the dynamic behavior, related with metallotropic phenomena, of the new complexes. 1H NMR variable-temperature studies of complexes 1, 6, and 8 have been carried out. For 8, only one static species is observed, while, for 1 and 6, two isomers are detected at low temperature. Different ΔGC? activation energies at the coalescence temperature have been determined and are ascribed to processes implying Pd-N bond ruptures. For 6, two different barriers are detected, corresponding to Pd-N(triazine) or Pd-N(pyrazole) bond ruptures. From the ΔGC? data, it is concluded that the main driving force of the hydrolysis process is the formation of a better coordinating ligand. The molecular structure of 4 has been determined by X-ray diffraction. The meso isomer, in which the two C-Me axes of the allylic groups are oriented in the same direction, is found in the solid state.
