211487-76-2Relevant academic research and scientific papers
On the question of mixed-valent states in ligand-bridged dinuclear organoplatinum compounds [RkPt(μ-L)PtRk]n, k = 2 or 4
Klein, Axel,Hasenzahl, Steffen,Kaim, Wolfgang,Fiedler, Jan
, p. 3532 - 3538 (1998)
Symmetrically dinuclear complexes between the bis-bidentate bridging ligands μ-L (μ-L = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) or 2,5-bis(1-phenyliminoethyl)pyrazine (bpip)) and the organoplatinum fragments PtMeS2 (Mes = mesityl), PtMe2, or PtMe4 were synthesized as deeply colored compounds. Low-energy charge-transfer transitions from metal d orbitale (Pt11) or metal-carbon σ bond combinations (PtIV) to low-lying π* orbitals of the π acceptor ligands are responsible for long-wavelength absorption maxima λmax(CT) > 700 nm. UV/Vis and EPR spectroelectrochemical results for reversible reduction processes indicate the formation of [PtIV]2(μ-L.-) and [PtII]2(μ-L.-) species, however, the latter exhibit a significant metal contribution according to a PtII/PtI formulation. Cyclic voltammetry reveals that the remarkable system [Mes2Pt(μ-bptz)PtMes2]n forms an enormously stabilized radical anion (n = 1-) with ΔE1/2 = 1250 V and Kc = 1021.2 and a PtIII/PtII mixed-valent state (n = 1+) with ΔE1/2 = 80 mV and Kc = 23. This small Kc value is attributed to the predominantly dσ orbital character of the redox orbitals on the Pt(II) centers.
