Bifunktionelle Cp∩N-Komplexe: ungewöhnliche Strukturen und elektronische Kommunikation in hochgradig präorganisierten Zweikernkomplexen

Abstract

Professor Lutz F. Tietze zum 60. Geburtstag gewidmetKomplexen von Cyclopentadienyl(Cp)-Liganden mit funktionellen Amino-oder Amidoseitenarmen wird in der Organometallchemie derzeit gro˚e Aufmerksamkeit geschenkt. [1, 2] W‰hrend der mit der Cp-Einheit verbundene Donorsubstituent in Systemen vom Typ A meistens die Aufgabe einer hemilabilen Chelatfunktion¸bernimmt, berichteten wir k¸rz-lich¸ber ein neues Konzept, bei dem ein Pyrazolat-Heterocyclus in bimetallischen Verbindungen vom Typ B zwei Cp-Einheiten verkn¸pft und somit zum einen als intramolekularer N-Donor, zum anderen als Br¸cke zwischen den beiden Metallionen fungiert. [3] Diese Strategie der formalen Ver-kn¸pfung zweier N-Donor-Ligandenkompartimente¸ber eine verbr¸ckende Pyrazolatgruppe wurde bereits erfolgreich beim Studium kooperativer Effekte in biomimetischen Koor-stand mit 60 mL Petrolether aufgenommen und durch eine Fritte mit Kieselgur filtriert. Aus der eingeengten Lˆsung wachsen bei À 28 8C 0.7 g (52 %) rote Kristalle von 2. Schmp. 95 ± 96 8C. Elementaranalyse (%): ber.

Electronic Coupling in a Highly Preorganized Bimetallic Complex Comprising Pyrazolate‐Bridged CpMn(CO)2 Moieties

“…Single crystals of K + 1 − ⋅0.9 THF obtained from THF/light petroleum were analyzed by Xray crystallography. As discussed previously,14 the crystals contain four independent (but similar) dimanganese( I ) units of the anticipated constitution per asymmetric unit—one of them is depicted in Figure 2.…”

“…We have recently reported a novel type of dinuclear [{CpMn(CO) 2 } 2 L] array, where L is a N,N′‐bridging pyrazolate that is covalently linked to the Cp spectator ligands at the manganese and spans the two Mn ions, thus giving a highly preorganized chelate arrangement in 1 − 14 15 since it can be described as a bimetallic version B in which the donor substituent tethered to the Cp moiety additionally serves a bridge function 16.…”

“…In the present context, the rigid chelate arrangement in 1 − was anticipated to preclude dissociation of its CpMn(CO) 2 L moieties, thus allowing a detailed investigation by various analytical methods of the electronic structure of the dimanganese system in its different oxidation states. Some aspects of the structural and electronic properties of 1 − have already been communicated 14…”

Redox Site Confinement in Highly Unsymmetric Dimanganese Complexes

“…Thus, our investigations on the neutral complexes 3 and 5 as well as on their monocations 3 + and 5 + were carried out with the hybrid B3LYP 22 and pure BP86 23 functionals and the all-electron basis sets with and without polarization functions. Both functionals are commonly used for the investigation of transition-metal compounds, also comprising the cases of open-shell mixed-valent species. 15b, All computations employed the unrestricted Kohn−Sham formalism. The basis sets used are of valence triple-ζ quality: 6-311G or 6-311G* for the main group elements 24 and Wachter's (14s9p5d)/[9s5p3d] or (14s9p5d1f)/[9s5p1d1f] (α f = 0.96) for the Mn atoms .…”

“…In the case of pyrazolate-based homobimetallic complexes, the two metal ions spanned by the heterocycle are in the same oxidation state in most cases. , It should be noted though that the pyrazolate bridge provides significant electronic coupling, and mutual metal oxidative deactivation upon oxidative addition to one of the two metals as well as fast electron transfer in mixed-valence species has been reported. , We studied in detail the dimanganese complex 1 - , which was shown to undergo two sequential one-electron metal-centered oxidations with fast intramolecular thermal electron transfer ( k ET ≈ 2.6 × 10 10 s -1 at 298 K) in the mixed-valent Mn I Mn II species, having a formal low-spin d 5 d 6 electronic configuration . In a further elaboration, the multifunctional system HL Mn , with both a CpMn(CO) 2 subunit and a {N 4 } donor compartment tethered to the central pyrazole, has been developed.…”