25005-95-2Relevant academic research and scientific papers
Palladium(II) and Platinum(II) Mononuclear Complexes and Tendency to Undergo Dehydrogenation of the Multiple N-Donor Ligand Di-(2-pyridyl)dihydropyrazine
Raciti, Edoardo,Donzello, Maria Pia,Viola, Elisa,Bassetti, Mauro,Pettiti, Ida,Bellucci, Noemi,Rizzoli, Corrado,Ercolani, Claudio
, p. 8893 - 8905 (2020)
The already known di(2-pyridyl)dihydropyrazine (dhdpp) was prepared and isolated also in the form of a bis-hydrated species, i.e., dhdpp·2H2O. As established by X-ray work, a small amount of single crystals of di(2-pyridyl)-pyrazine (dpp) was also obtained from the mother liquors, this testifying the possibility of a dehydrogenation process dhdpp → dpp in the absence of a catalyst. Using dhdpp as a ligand, mononuclear metal derivatives of formula [(dhdpp)MCl2]·xH2O (M = PdII, PtII) were obtained as stable-to-air solids, studied by X-ray powder, IR, UV-visible, and 1H NMR spectra, and proved to exhibit a N2MCl2 coordination site involving one pyridine and one pyrazine N atom ("py-pyz"coordination). An interesting relationship has been established in terms of the observed types of coordination with the analogs of di(2-pyridyl)-pyrazine (dpp) formulated as [(dpp)MCl2]·3H2O, proved also by 1H NMR spectra to exhibit the "py-pyz"mode of coordination. Attempts to isolate from the reaction of dhdpp with Pd(OAc)2 the corresponding mononuclear derivatives were shown to lead, as definitely supported by 1H NMR spectral data and crystallographic work, to the exclusive formation of the corresponding dpp complex [(dpp)Pd(OAc)2]·5H2O ("py-pyz"coordination site), this proving the tendency of dhdpp to generate dpp under different reaction conditions. The promoted conversion of dhdpp into dpp in the complex was examined by sequential NMR analysis and established to be determined by Pd(OAc)2 which plays the role of catalyst. The new salt-like species [(CH3)(dhdpp)PdI2](I)·7H2O, prepared starting from [(dhdpp)PdCl2] in its reaction with CH3I, allowed the separation from the mother liquors of small brown crystals identified on the basis of X-ray analysis as the already known complex of formula [(dpp)PdI2] ("py-py"coordination), this result once again outlining the tendency of dhdpp to be dehydrogenated to dpp.
Ru(ii) water oxidation catalysts with 2,3-bis(2-pyridyl)pyrazine and tris(pyrazolyl)methane ligands: Assembly of photo-active and catalytically active subunits in a dinuclear structure
Bortoluzzi, Marco,Campagna, Sebastiano,De Palo, Alice,Guelfi, Massimo,La Ganga, Giuseppina,Marchetti, Fabio,Nastasi, Francesco,Pampaloni, Guido,Puntoriero, Fausto
, p. 3341 - 3352 (2020/03/19)
Two mononuclear Ru(ii) complexes, i.e. [RuCl(κ3N-terpy)(κ2N-dpp)]PF6 ([1]PF6; terpy = 2,2′:6′,2′′-terpyridine; dpp = 2,3-bis(2′-pyridyl-pyrazine) and [RuCl(κ3N-tpm)(κ2N-dpp)]Cl ([2]Cl; tpm = tris(1-pyrazolyl)methane), and one dinuclear complex, i.e. [Ru2Cl(κ3N-tpm)(μ-κ2N:κ2N-dpp)Ru(κ2N-bpy)2][PF6]3 ([3][PF6]3; bpy = 2,2′-bipyridine), have been synthesized and their water oxidation catalytic properties have been investigated. A combined DFT and experimental (35Cl NMR and conductivity measurements) study aimed to elucidate the nature of [1]+ and [2]+ in aqueous solution has also been performed, indicating that one water molecule is allowed to enter the first coordination sphere of [2]+ in the ground state, replacing one tpm nitrogen. Conversely, in the case of [1]+, water coordination, assumed to be needed for the water oxidation process, presumably occurs following the oxidation of the metal. For all complexes, a catalytic wave has been detected in acetonitrile/water 1 : 1 (v/v) solution in the range 1.4-1.7 V vs. SCE. In all cases, water oxidation (investigated at pH -1, respectively) of the complexes are higher than those of the benchmark [Ru(LLL)(LL)(OH2)]2+-type species (LLL and LL are tridentate and bidentate polypyridine ligands, respectively), which is [Ru(terpy)(bpm)(OH2)]2+.
