Synthesis of Tetranuclear, Four-Coordinate Manganese Clusters with “Pinned Butterfly” Geometry Formed by Metal-Mediated N−N Bond Cleavage in Diphenylhydrazine

Abstract

The preparation of four-coordinate tetramanganese-amide-hydrazide clusters is described. Reaction of Mn(NR(2))(2) (R = SiMe(3)) with N,N'-diphenylhydrazine resulted in the formation of a black intermediary mixture that converted to a four-coordinate tetranuclear "pinned butterfly" cluster, Mn(4)(μ(3)-N(2)Ph(2))(2)(μ-N(2)Ph(2))(μ-NHPh)(2)(THF)(4). This compound was isolated in ~90% yield and identified by single-crystal X-ray diffraction analysis. In pyridine, the THF ligands were replaced, giving the pyridyl complex Mn(4)(μ(3)-N(2)Ph(2))(2)(μ-N(2)Ph(2))(μ-NHPh)(2)(py)(4). Charge counting considerations indicate that the clusters had gained two protons and two electrons in addition to the formative fragments. Isolation of the black mixture was achieved by extraction techniques from a reaction with a decreased loading of hydrazine run at low temperatures with decreased solvent polarity. The black mixture was characterized by FT-IR, UV-vis, and (1)H NMR spectroscopy. In addition, an isolable, colorless dimer, Mn(2)(μ-NHPh)(2)(NR(2))(2)(THF)(2), was present in the mixture and identified by single-crystal X-ray diffraction. These intermediates are discussed in light of possible mechanisms for formation of the tetranuclear cluster.

Control of cerium oxidation state through metal complex secondary structures

“…Zdilla and coworkers recently reported a Li + heterobimetallic diphenylhydrazido complex that effectively stabilized high valent Mn( iv ) cations despite the reducing character of the ligand and the oxidizing character of Mn( iv ) (see Scheme 1 ). 38 – 40 Intrigued by these results and the relative scarcity of electrochemical properties reported for anionic nitrogen donors at cerium, 41 we hypothesized that 1,2-diphenyl hydrazido ligands would similarly form cerium complexes with secondary structures governed by alkali metal cations.…”

A DFT/B3LYP study of the mechanisms of the O2 formation reaction catalyzed by the [(terpy)(H2O)MnIII(O)2MnIV(OH2)(terpy)](NO3)3 complex: A paradigm for photosystem II

“…Although many complexes have been considered as structural models for the OEC [7][8][9][10][11][12][13][14][15][16], only a few act also as functional models [17][18][19][20][21][22][23][24][25][26]. evolution reaction catalyzed by the terpy complex [6].…”

Synthesis, and characterization of low- and high-spin manganese(II) complexes of polyfunctional adipoyldihydrazone: Effect of coordination of N-donor ligands on stereo-redox chemistry

“…The lower oxidation state species of manganese(II) are commonly 6-coordinate. Coordination number four with a distorted square-planar or tetrahedral geometry is known for the high-spin Mn(II) [12,13] but uncommon for low-spin manganese(II). We report herein, a lowspin Mn(II) complex with square-planar geometry and provide examples of high-spin Mn(II) complexes with octahedral geometry.…”