Charakterisierung eines Oxo(porphyrinato)‐mangan(IV)‐Komplexes mit Röntgenabsorptionsspektroskopie

Abstract

ZUSCHRIFTENcher als das klassische 1-Boraallyl-Kation 12: der sehr starke Elektronenmangel am C+-Zentrum in 11" fiihrt zur Ubertragung eines Hydrid-Ions, also zu einer Umlagerung, dem Extremfall[61 einer agostischen Wechselwirkung" 61.Die rnit 3u,, 10, und 11, bzw. 10, und 11, isoelektronischen Dikationen 13, bzw. 13, rnit planar-tetrakoordinierten C-Atomen sind 14.4 bzw. 14.6 kcal mol-' energiereicher als das planare Allen-Dikati~n["~. Die Realisierung von Anti-van't-Hoff/Le-Bel-Geometrie erfordert also elektropositive Elemente: aui3er Metallen ist auch Bor geeignet. 3828-3836. Verbindungen des Typs I werden in der Literatur nicht explizit denen mit planar-tetrakoordinierten C-Atomen zugeordiiet. Ihre C-H-8-agostische Wechselwirkung entspricht aber den C-E-P-agostischen Wechselwirkungen in 2: Die 8-C-M-Abstindeals Kriterium fur die vierte Koordination des 8-C-Atomssind in 1 nur wenig linger als die in 2.

Spin Transition in a Manganese(III) Porphyrin Cation Radical, Its Transformation to a Dichloromanganese(IV) Porphyrin, and Chlorination of Hydrocarbons by the Latter

“…This effect, which cannot be explained by simple ligand field considerations, could also be responsible for the small differences between the high- and low-spin states in the present case. Unfortunately, we were not successful in obtaining X-ray data for complex 3 , which could aid in the understanding of its interesting magnetic properties. , …”

“…The bond length between the metal and the pyrrole nitrogens is most distinctive for differentiation between high-spin (Fe−N ≥ 2.06 Å) and intermediate- or low-spin (Fe−N ≤ 2.00 Å) iron(III) porphyrins. 37a,40a This is however not expected in the present case, since the d x 2 - y 2 orbital is not occupied in both high- and low-spin Mn(III). It is well documented that the metal−nitrogen bond lengths are very similar (Mn−N ∼ 2.00 Å) in 5- and 6-coordinated Mn(III) porphyrins 40a,b in a Mn(III) porphyrin cation radical 15 and even in Mn(IV) porphyrins 40c…”

Water as an Oxygen Source: Synthesis, Characterization, and Reactivity Studies of a Mononuclear Nonheme Manganese(IV) Oxo Complex

“…This bond length is similar to that found in [Mn IV (H 3 buea)(O)] − (1.706 Å; determined by DFT calculations)7b and those found in Mn IV or Mn V oxo porphyrins (ca. 1.68 Å; determined by EXAFS analysis),4b, 19 in which the MnO bond has a double‐bond character.…”