Michael U. Triller

Catalytic oxidation of 3,5-Di-tert-butylcatechol by a series of mononuclear manganese complexes: synthesis, structure, and kinetic investigation.

The manganese compounds [Mn(bpia)(OAc)(OCH 3 )](PF 6 ) (1), [Mn(bipa)(OAc)(OCH 3 )](PF 6 ) (2), [Mn(bpia)(Cl) 2 ](ClO 4 ) (3), [Mn(bipa)(Cl) 2 ](ClO 4 ) (4), [Mn(Hmimppa)(Cl) 2 ].CH 3 OH (5), and [Mn(mimppa)(TCC)].2CHCl 3 (6) (bpia= bis-(picolyl)(N-methylimidazole-2-yl)amine; bipa = bis(N-methylimidazole-2-yl)(picolyl)amine; Hmimppa = ((1-meth-ylimidazole-2-yl)methyl)((2-pyridyl)methyl)(2-hydroxyphenyl)amine; TCC = tetrachlorocatechol) were synthesized and characterized by various techniques such as X-ray crystallography, mass spectrometry, IR, EPR, and UV/vis spectroscopy, cyclic voltammetry, and elemental analysis. 1 and 2 crystallize in the triclinic space group P1 (No. 2), 4 and 6 crystallize in the monoclinic space group P2 1 /n (No. 14), and 5 crystallizes in the orthorhombic space group Pna2 1 . Complexes 1-4 are structurally related to the proposed active site of the manganese-dependent extradiol-cleaving catechol dioxygenase exhibiting an N 4 O 2 donor set (1 and 2) or N 4 Cl 2 donor set (3 and 4). Cyclic voltammetric data show that the substitution of oxygen donor atoms with chloride causes a shift of redox potentials to more positive values. These compounds show high catalytic activity regarding the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone exhibiting saturation kinetics at high substrate concentrations. The turnover numbers k c a t = (86 ′ 7) h - 1 (1), k c a t = (101 ′ 4) h - 1 (2), k c a t = (230 ′ 4) h - 1 (3), and k c a t = (130 ′ 4) h - 1 (4) were determined from the double reciprocal Lineweaver-Burk plot. Compounds 5 and 6 can be regarded as structural and electronic Mn analogues for substituted forms of Fe-containing intradiol-cleaving catechol dioxygenases. To our knowledge 5 is the first mononuclear Mn(II) compound featuring an N 3 OCl 2 donor set.

Reactions of Polyfluoroarenes with MenE‐MMe3 Reagents (MenE = Me2As, Me2P, Me2N, and MeS; M = Si, Sn): Synthesis of Polyfluoroaryl MenE Compounds

Trimethylsilyldimethylarsane Me3SiAsMe2 was used as a reagent for the substitution of fluorine in polyfluoroarenes C6F5X (X = F, H, Cl) and C5NF5 by the Me2As group. The reactions occur between 50 — 180 °C, either in benzene or without solvent, to give as a rule 4-X-1-(dimethylarsano)tetrafluorobenzenes XC6F4AsMe2, (1—3) and 4-dimethylarsano-tetrafluoropyridine C5NF4AsMe2 (4), respectively, in yields between 43 and 94 %. In the case of C6F6, also double substitution is observed affording 1, 4-bis(dimethylarsano)tetrafluorobenzene 5 in addition to the monosubstituted derivative. The time and temperature dependencies of the reactions increase in the sequence: C6F6< C6F5H < C6F5Cl < C5NF5. The arsanes 1 and 4 were transformed to the potentially valuable bidentate ligands 1-(dimethylarsano)-4-(dimethylphosphano)tetrafluorobenzene 6 and 4-(dimethylarsano)-2-(dimethylphosphano)trifluoropyridine 8 by reaction with trimethylsilyl-dimethylphosphane Me3SiPMe2. 6reacts with oxygen to yield the corresponding phosphane oxide 7. Trimethylsilyl-dimethylamine Me3SiNMe2 also was successfully tested as a reagent for the dimethylamination of polyfluoroarenes C6F5X [X = F, H, Cl, CF3, P(S)Me2], 1-P(S)Me2-4-H-C6F4 and 4-X-C5NF4 [X = F, PMe2, P(S)Me2]. Sulfuration of the new Me2P derivatives 8 and 20 leads to the corresponding thiophosphanes 9 and 21 (Schemes 2 and 3). Furthermore, the recently reported very efficient one-pot synthesis of Me2P substituted polyfluoroarenes (e.g. XC6F4PMe2 with X = F, Me2PC6F4) was extended to the preparation of Me2As and MeS derivatives of pentafluoropyridine using a mixture of Me3SnH, As2Me4 (or S2Me2) and C5NF5 as precursors for the one-pot reaction. The expected products 4-(dimethylarsano)tetrafluoropyridine 4 and 4-(methylthio)tetrafluoropyridine 22, respectively, were obtained in 84 and 82 % isolated yields. The novel compounds were characterized by spectroscopic (NMR, MS) and analytical data. Compounds 5, 7, 9 and 21 could be isolated in form of single crystals and their structures have been studied by X-ray diffraction. Reaktionen von Polyfluorarenen mit MenE—MMe3-Reagenzien (MenE = Me2As, Me2P, Me2N, MeS; M = Si, Sn): Synthese von MenE-substituierten Polyfluorarenen Trimethylsilyl-dimethylarsan Me3SiAsMe2 wurde bei Polyfluorarenen C6F5X (X = F, H, Cl) und Perfluorpyridin C5NF5 als Reagenz fur die Substitution von Fluor durch die Me2As-Gruppe eingesetzt. Die Reaktionen wurden in Benzol oder ohne Losungsmittel bei Temperaturen zwischen 50 und 180 °C durchgefuhrt und liefern in der Regel die 4-X-1-(Dimethylarsano)tetrafluorbenzole XC6F4AsMe2 (1 — 3) bzw. 4-Dimethylarsanotetrafluorpyridin C5NF4AsMe2 (4) in Ausbeuten von 43 — 94 %. Im Fall von C6F6 wird auch Zweifachsubstitution zum 1, 4-Bis(dimethylarsano)tetrafluorbenzol 5 beobachtet. Die Reaktivitat, gemessen am Zeitbedarf und an der Temperaturabhangigkeit der Reaktionen, wird von der Art des Polyfluorarens bestimmt und nimmt in der Reihe C6F6 < C6F5H < C6F5Cl < C5NF5 zu. Die Arsane 1 und 4 wurden mit Trimethylsilyl-dimethylphosphan Me3SiPMe2 zu den heterosubstituierten Derivaten 1-(Dimethylarsano)-4-(dimethylphosphano)tetrafluorbenzol 6 bzw. 4-(Dimethylarsano)-2-(dimethylphosphano)-trifluorpyridine 8 umgesetzt, die als potenzielle zweizahnige Liganden von Interesse sind. 6 reagiert mit Sauerstoff zum entsprechenden Phosphanoxid 7. Trimethylsilyl-dimethylamin Me3SiNMe2 wurde als Reagenz fur die Dimethylaminierung der Polyfluorarene C6F5X [X = F, H, Cl, CF3, P(S)Me2], 1-P(S)Me2-4-HC6F4 and 4-X-C5NF4 [X = F, PMe2, P(S)Me2] ebenfalls untersucht. Durch Sulfurierung der Me2P-Derivate 8 und 20 werden die Thiophosphane 9 und 21 erhalten (Schemata 2 und 3). Auserdem wurde die vor kurzem entwickelte Eintopf-Synthese fur Me2P substituierte Polyfluorarene (z. B. XC6F4PMe2 mit X = F, Me2PC6F4) auf die Darstellung von Me2As- und MeS-Derivaten des Pentafluorpyridins ausgedehnt: Als Edukte fur die Eintopf-Reaktionen wurden Me3SnH, As2Me4 (oder S2Me2) und C5NF5 verwendet. Die erwarteten Produkte 4-(Dimethylarsano)tetrafluorpyridin 4 bzw. 4-(Methylthio)tetrafluorpyridin 22 wurden in 84- bzw. 82- %iger Ausbeute isoliert. Die neuen Verbindungen wurden durch spektroskopische (NMR, MS) und analytische Daten charakterisiert. Die Vertreter 5, 7, 9 und 21 konnten in Form von Einkristallen isoliert werden; ihre Strukturen wurden durch Rontgenbeugung aufgeklart.

A Tetranuclear Manganese Cluster with a Star‐Shaped Mn4O6 Core Motif: Directed Synthesis using a Mononuclear Precursor Complex

The tetranuclear manganese(II) complex [Mn4(ppi)6](BPh4)2 (2) (Hppi = 2-pyridylmethyl-2-hydroxy phenylimine) is prepared by using the precursor complex [Mn(ppi)2]·H2O (1). Based on UV/Vis- and IR-spectroscopy data in combination with mass spectrometry it has been concluded that 1 is a mononuclear neutral MnII complex, in which two ppi ligands chelate the manganese atom. Compound 2 crystallizes in the triclinic space group P1¯ (no. 2), with a = 17.500(3), b = 17.955(4), c = 19.101(4) A, α = 113.79(3)°, β = 111.33(3)°, γ = 93.91(3)°, V = 4950(2) A3 and Z = 2. In the tetranuclear [Mn4(ppi)6]2+ complex cation Mn(1), Mn(2), and Mn(3) are equivalently coordinated by two deprotonated Hppi ligands leading to a N4O2 donor set. The environment of the central Mn(4) is formed by coordination of three [Mn(ppi)2] fragments resulting in a phenoxo bridged star-shaped Mn4O6 core motif. The average distance of directly adjacent manganese ions is 3.310 A, whereas the average distance of Mn(1), Mn(2), and Mn(3) among each other is 5.732 A.

Cover Picture: Angew. Chem. Int. Ed. 14/2002

The cover picture shows a polyhedral representation of a polyoxovanadate core {V6O13(OMe)6}2−, which is linked to two vanadyl moieties. These are coordinated through the N2O2 donor set of organic ligands, which additionally stabilize the hexavanadate through two hydrogen bonds. This compound can be considered as “bridging the gap” between polyoxometalates and classic coordination compounds. Fittingly, in the background, is Mungsten railway bridge near Wuppertal, Germany, which links the towns of Remscheid and Solingen. The bridge, which was built in 1897, at a height of 107 m, an arch width of 170 m, and a total length of 500 m was considered an engineering masterpiece of its time in Europe. More about the successful linkage of two important classes of compounds is reported in the communication by M. Piepenbrink, M. U. Triller, N. H. J. Gorman, and B. Krebs on pp. 2523 ff.