Although similar to carbon monoxide,the chemistry of homoleptic nitrogen monoxide complexes is fundamentally unexplored compared to their carbonyl analogues.H erein we report the synthesis of the first truly homoleptic transitionmetal nitrosyl cation as the salt of the weakly coordinating anions (WCAs) [Al(OR F ) 4 ] À and [F{Al(OR F ) 3 } 2 ] À (R F = C-(CF 3 ) 3 ). These salts are easily accessible in good yields,p hase pure,a nd were fully characterized by IR/Raman, NMR and UV/Vis spectroscopya sw ell as single-crystal and powder Xray diffraction. They may serve as unprecedented simple model systems for theoretical and experimental studies of nitrosyl complexes. Angewandte Chemie Communications 9587Angew.C hem. Int.E d. 2019, 58,9 586 -9589
Trotz der ¾hnlichkeit zu Kohlenmonoxid ist die Chemie von homoleptischen Stickstoffmonoxidkomplexen im Unterschied zu ihren Carbonylanaloga bislang grundlegend unerforscht. Hier beschreiben wir die Synthese des ersten echten homoleptischen Übergangsmetallnitrosylkomplexes als Salz der schwachk oordinierenden Anionen (WCAs) [Al(OR F ) 4 ] À und [F{Al(OR F ) 3 } 2 ] À (R F = C(CF 3 ) 3 ). Diese Salze sind in guten Ausbeuten phasenrein zugänglichu nd wurden vollständig durch IR/Raman-, NMR-und UV/Vis-Spektroskopie sowiem ittels Einkristallstrukturanalyse und Pulverdiffraktometrie charakterisiert. Sie kçnnten als bisher beispiellose Modellsysteme fürtheoretische und experimentelle Studien zu Nitrosylkomplexen fungieren.ImLaufe der letzten Jahrzehnte waren Übergangsmetallnitrosylkomplexe hauptsächlich wegen der wichtigen Rolle von NO in biochemischen Prozessen im Fokus. [1,2] Nahezu 4000 Kristallstrukturen von Übergangsmetallnitrosylkomplexen mit mindestens einem NO-Liganden sind in der CCSD (Stand 05/2019) hinterlegt. Obwohl -o der gerade weil -s ie so vielzählig sind, fällt auf,d ass bis heute nur ein einziger homoleptischer und vollständig charakterisierter Nitrosylkomplex publiziert wurde:d as anionische [Fe(NO) 4 ] À (Tabelle 1). [3] Dies ist gerade im Vergleich mit der sehr gut untersuchten Chemie der artverwandten Carbonylkomplexe verwunderlich, da dort seit langer Zeit zahlreiche Beispiele von anionischen, neutralen oder kationischen homoleptischen Kom-Angewandte Chemie
The triruthenium oxo clusters [Ru3(OAc)6O(L)3]+ and [Ru3(OAc)6O(L)2(CO)] possess unique electronic characteristics that vary based on the ligands L. Here we report an investigation of the structural, electrochemical, and optical properties of clusters with imidazole, benzimidazole, and 4‐phenylpyridine ligands. The complexes [Ru3(OAc)6O(L)3]+ [1+: L = imidazole (im); 2+: L = benzimidazole (benzim); 3+: L = 4‐phenylpyridine (4PP)] and [Ru3(OAc)6O(L)2(CO)] (1‐CO and 3‐CO) were synthesized by reaction of either [Ru3(OAc)6O(MeOH)3]+ or [Ru3(OAc)6O(MeOH)2(CO)], respectively, with the corresponding heterocycle. We further discovered that [3]OAc could be reduced to the mixed‐valence neutral state 3 by refluxing the complex under nitrogen in methanol. Single‐crystal X‐ray structure analysis of hexa‐μ2‐acetato‐μ3‐oxido‐tris(1H‐imidazole)triruthenium hexafluorophosphate acetonitrile hemisolvate, [Ru3(C2H3O2)6O(C3H4N2)3]PF6·0.5CH3CN, [1]PF6, hexa‐μ2‐acetato‐carbonylbis(1H‐imidazole)‐μ3‐oxido‐triruthenium methanol monosolvate, [Ru3(C2H3O2)6O(C3H4N2)(CO)]·CH3OH, 1‐CO, hexa‐μ2‐acetato‐μ3‐oxido‐tris(4‐phenylpyridine)triruthenium pentahydrate, [Ru3(C2H3O2)6O(C11H9N)3]·5H2O, 3, and hexa‐μ2‐acetato‐carbonyl‐μ3‐oxido‐bis(4‐phenylpyridine)triruthenium methanol monosolvate, [Ru3(C2H3O2)6O(C11H9N)2(CO)]·CH3OH, 3‐CO, show the expected triruthenium μ3‐oxo core and N‐coordination of the ligands. Cyclic voltammetry revealed quasi‐reversible and irreversible redox couples in [1]PF6, 1‐CO, and [2]PF6, while [3]PF6 and 3‐CO exhibit reversible redox couples. The optical properties of these richly colored species were investigated using UV–Vis spectroscopy.
The discorhabdin natural products are a large subset of pyrroloiminoquinone alkaloids with a myriad of biological activities. Despite garnering much synthetic attention, few members have thus far been completed, with none featuring a bridging carbon–nitrogen bond that is found in numerous discorhabdins, including discorhabdin V. Here we report the first total synthesis and full stereochemical assignment of (+)-discorhabdin V in 13 linear steps. To access the pyrroloiminoquinone we developed a convergent N-alkylation/oxidative aminocyclization/bromination cascade that joins two key components, which are both made on multigram scale. An intramolecular Heck reaction then forms the quaternary carbon center in an intermediate containing the carbon–nitrogen bridge, and a reductive N,O-acetal cyclization sequence introduces the final piperidine ring. Furthermore, we have established the relative stereochemistry of (+)-discorhabdin V through experimental NOESY data and DP4 NMR probability calculations. The absolute configuration of the natural product has also been determined via circular dichroism and the use of an amino acid-derived chiral starting material. Our work represents the first report of a total synthesis of a nitrogen-bridged discorhabdin and paves the way for future biological evaluation of such compounds.
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