title: Pyrazole and Pyrazolate as Ligands in the Synthesis and Stabilization of New Palladium(II) and (III) Compounds.
abstract: The versatility of pyrazole/pyrazolate as ligands has allowed the synthesis and the structural characterization of four different types of new orthometalated palladium compounds, for which DFT calculations have been performed in order to investigate their relative stabilities. [Pd2{μ-(C6H4)PPh2}2{μ-(R,R'2pz)}2] (R = R' = H, 2a; R = Br, R' = H, 2b; R = CH3, R' = H, 2c; R = H, R' = CH3, 2d; R = Br, R' = CH3, 2e) compounds with exo-bidentate pyrazolatos are the first paddlewheel dinuclear palladium(II) compounds with pyrazolato bridging ligands described and characterized in the literature. In the process of the synthesis of 2a, a new tetranuclear intermediate compound, [Pd4{μ-(C6H4)PPh2}4(μ-pz)2(μ-OH)2] (3a), has been isolated and structurally characterized. Compounds of the general formula [Pd2{μ-(C6H4)PPh2}2Br2(R,R'2pzH)2] (R = R' = H, 4a; R = Br; R' = H, 4b; R = CH3; R' = H, 4c; R = H; R' = CH3, 4d; R = Br; R' = CH3, 4e) with pyrazoles as monodentate ligands have also been obtained, in which, according to the QTAIM analysis, additional Br···HNpz weak interactions stabilize their structure. The tetranuclear Pd2Ag2 compounds, [Pd2{μ-(C6H4)PPh2}2{μ-(R,R'2pz-Ag-R,R'2pz)}2] (R = R' = H, 5a; R = Br; R' = H, 5b; R = CH3, R' = H, 5c), showed a distorted tetrahedron disposition of the metal atoms. The QTAIM analysis revealed an enhanced stability because of additional metal-metal interactions. New palladium(III) compounds, [Pd2{μ-(C6H4)PPh2}2{μ-(R,R'2pz)}2Cl2] (R = R' = H, 6a; R = Br, R' = H, 6b) were also synthesized by oxidation of compounds 2 with PhICl2. DFT calculations highlighted their greater stability compared to that of similar compounds with N,N-donor ligands, such as formamidinatos and triazenidos.
authors.affiliation: Departament de Química Inorgànica, Universitat de València , Dr. Moliner 50, 46100-Burjassot, València, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Estevan
authors.affiliation: Department of Chemistry, University of Eastern Finland , Joensuu Campus, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Pipsa
authors.initials: P
authors.lastname: Hirva
authors.affiliation: Department of Chemistry, University of Eastern Finland , Joensuu Campus, P.O. Box 111, FI-80101 Joensuu, Finland.
authors.forename: Albert
authors.initials: A
authors.lastname: Ofori
authors.affiliation: Departament de Química Inorgànica, Universitat de València , Dr. Moliner 50, 46100-Burjassot, València, Spain.
authors.forename: Mercedes
authors.initials: M
authors.lastname: Sanaú
authors.affiliation: Departament de Química Inorgànica, Universitat de València , Dr. Moliner 50, 46100-Burjassot, València, Spain.
authors.forename: Tanja
authors.initials: T
authors.lastname: Špec
authors.affiliation: Departament de Química Inorgànica, Universitat de València , Dr. Moliner 50, 46100-Burjassot, València, Spain.
authors.forename: MaAngeles
authors.initials: M
authors.lastname: Úbeda