The nature of reduced and excited states of .pi.-electron-deficient complexes between tricarbonylhalorhenium and diimine ligands

Reversible radical complex formation of an organometallic diplatinum(IV) compound

“…Previous studies of tetrazine complexes [11] showed generally very large differences of >1.0 V between the first and second reduction while the (irreversible) oxidation of the PtMe 3 X group must involve the halide or carbanionic ligands. The reduction potential compares with about À0.15 V vs. [FeCp 2 ] +/ for the related, similarly neutral [(l-bptz){fac-ReBr(CO) 3 } 2 ], bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine, believed to be studied as the anti isomer [12]. In both cases it is remarkable that the first reduction step does not appreciably labilize the bromide ligands which would constitute excellent leaving groups.…”

“…While odd electron platinum species like Pt III are typically characterized by extremely shifted g factors [14] or even by EPR silence [15] the tetrazines exhibit the distinct localization of an added electron on the four nitrogen atoms, leading to typically resolved spectra [11,12]. For symmetrically dinuclear bis-chelate complexes of bptz or bmptz radical anions two EPR hyperfine coupling constants from two pairs of 14 N (tetrazine) nuclei (I = 1) are thus expected, additional coupling with the 195 Pt nuclei (I = 1/2, 33.8% natural abundance) is usually detectable [16,17] because of the large isotropic hyperfine constant a = 1227.84 mT [18].…”

“…close to 2.004, suggests that the heavy Pt and Br atoms with their very large spin-orbit coupling constants do not appreciably contribute to the singly occupied molecular orbital. However, the hyperfine interaction does not only involve two pairs of 14 N (tetrazine) nuclei with typical [11,12] coupling constants of 0.37 and 0.74 mT, it also requires the inclusion of 195 Pt coupling (2.35 mT, 2 Pt nuclei) and interaction with the 79,81 Br isotopes (0.55 mT, 2 Br) with their nuclear spin of I = 3/2 [18]. The chelate situation with the binding to two equivalent spin bearing tetrazine nitrogen atoms Table 1 Selected bond distances and angles for anti-[(l-bmptz){fac-PtBrMe 3 } 2 ] (for numbering see (Fig.…”

Metallorganische 5d6-Übergangsmetallkomplexe von zwei 1-Methyl-(2-alkylthiomethyl)-1H-benzimidazol-Liganden: Strukturen und elektrochemische OxidationProfessor Joachim Strähle zum 65. Geburtstag gewidmet

“…In beiden Verbindungen ist das Rhenium-Zentralatom annähernd oktaedrisch konfiguriert, wobei die CarbonylColiganden wie erwartet und schwingungsspektroskopisch ebenfalls bestätigt facial [10,11,24,25] angeordnet sind. Die Kohlenstoffatome in trans-Stellung zum Thioether-Schwefelatom weisen einen etwas längeren Abstand zum Rhenium-Zentralatom auf.…”

“…Die Tricarbonylchlororhenium(I)-Fragmente sind elektronenreich, stabilisieren jedoch auch Radikalanion-Liganden [10,11]; in Verbindung mit ungesättigten Chelatliganden vom Typ des 2,2'-Bipyridins sind sie befähigt, die photochemische oder elektrochemische Reduktion von CO 2 zu katalysieren [12,13]. Eine reversible Oxidation derartiger Komplexe wurde nur selten beschrieben [11]; wir berichten über entsprechende Untersuchungen bei den vorliegenden Verbindungen.…”