Mechanistic Elucidation of the Stepwise Formation of a Tetranuclear Manganese Pinned Butterfly Cluster via N–N Bond Cleavage, Hydrogen Atom Transfer, and Cluster Rearrangement

Abstract

A mechanistic pathway for the formation of the structurally characterized manganese-amide-hydrazide pinned butterfly complex, Mn4(μ3-PhN-NPh-κ(3)N,N')2(μ-PhN-NPh-κ(2)-N,N')(μ-NHPh)2L4 (L = THF, py), is proposed and supported by the use of labeling studies, kinetic measurements, kinetic competition experiments, kinetic isotope effects, and hydrogen atom transfer reagent substitution, and via the isolation and characterization of intermediates using X-ray diffraction and electron paramagnetic resonance spectroscopy. The data support a formation mechanism whereby bis[bis(trimethylsilyl)amido]manganese(II) (Mn(NR2)2, where R = SiMe3) reacts with N,N'-diphenylhydrazine (PhNHNHPh) via initial proton transfer, followed by reductive N-N bond cleavage to form a long-lived Mn(IV) imido multinuclear complex. Coordinating solvents activate this cluster for abstraction of hydrogen atoms from an additional equivalent of PhNHNHPh resulting in a Mn(II)phenylamido dimer, Mn2(μ-NHPh)2(NR2)2L2. This dimeric complex further assembles in fast steps with two additional equivalents of PhNHNHPh replacing the terminal silylamido ligands with η(1)-hydrazine ligands to give a dimeric Mn2(μ-NHPh)2(PhN-NHPh)2L4 intermediate, and finally, the addition of two additional equivalents of Mn(NR2)2 and PhNHNHPh gives the pinned butterfly cluster.

Protic Ruthenium Tris(pyrazol-3-ylmethyl)amine Complexes Featuring a Hydrogen-Bonding Network in the Second Coordination Sphere

“…The addition of a slight excess of 1,2-diphenylhydrazine to 2 afforded the aniline complex [RuCl­(PhNH 2 )­(LH 3 )]Cl ( 5 ), as shown in Scheme . The concurrent formation of equimolar amounts of free aniline and azobenzene per 5 was confirmed by the 1 H NMR spectrum Figure c depicts the crystal structure of 5 .…”

Synthesis and Characterization of Bioinspired [Mo2Fe2]–Hydride Cluster Complexes and Their Application in the Catalytic Silylation of N2

“…GC/GC-MS analyses were acquired on aS himadzu GCMS-2010SE. Cp*Mo(PMe 3 )(H) 5 (1), [11] Fe{N-(SiMe 3 ) 2 } 2 , [12] Mn{N(SiMe 3 ) 2 } 2 , [27] HSTip, [28] and HSBtp [29] were prepared according to literature procedures. All other chemicals were purchased from common commercial sources and used without further purification.…”

Structure of a pentamanganese(II)–phenoxide cluster with a central five-coordinate oxide: MnII 5(μ-OPh)6(μ3-OPh)2(μ5-O)(Py)6·Py (Py is pyridine)

“…Crystals of (I) were isolated during experiments to generate phenolic versions of amide/hydrazide manganese cluster compounds (Hamilton et al, 2014). The crystals were isolated from a reaction mixture of Mn[N(SiMe 3 ) 2 ] 2 (175 mg, 0.520 mmol), phenol (25 mg, 0.27 mmol) and N,N 0 -diphenylhydrazine (72 mg, 39 mmol) in pyridine (4 ml).…”