Hydrogen Bonds around M(μ‐O)₂M Rhombs: Stabilizing a {Co^III(μ‐O)₂Co^III} Complex at Room Temperature

Abstract

cysteine-containing dipeptides in high yield and without significant loss of chirality at the C2-exomethine carbon atom. Finally, the application of this method to one-pot tandem dehydrocyclizations afforded a thiazole±thiazoline product in good overall yield and with excellent stereocontrol. Experimental SectionGeneral procedure for synthesis of thiazolines: Trifluoromethanesulfonic anhydride (50 mL, 0.3 mmol) was added slowly to a solution of triphenylphosphane oxide (167 mg, 0.6 mmol) in dry CH 2 Cl 2 (2 mL) at 0 8C. The reaction mixture was stirred for 10 min at 0 8C and then adjusted to the desired reaction temperature, followed by addition of the fully protected cysteine N-amide (0.2 mmol). The reaction progress was monitored by TLC. The reaction mixture was quenched with 10 % aqueous NaHCO 3 solution. The aqueous layer was extracted with CH 2 Cl 2 , and the combined organic layers were dried over Na 2 SO 4 , filtered, and concentrated. The resultant crude product was purified by flash chromatography with EtOAc/hexanes. More details and characterization data of the products can be found in the Supporting Information.

A New Domain of Reactivity for High‐Valent Dinuclear [M(μ‐O)2M′] Complexes in Oxidation Reactions

“…In contrast, a nearly planar Ni 2 O 2 structure ( φ =179.8°; Table S2) is predicted by DFT for 3 , which may explain the strong antiferromagnetism leading to an S= 0 ground state. Similar diminution of antiferromagnetic couplings due to a folded Co 2 O 2 core have been observed earlier ,. Moreover, the Co–Co separation of 2.6715 Å (DFT: 2.66 Å) in 4 is significantly shorter than the DFT calculated Ni–Ni separation of 2.77 Å (Table S9) for 3 .…”

Enhancement of C−H Oxidizing Ability in Co–O2 Complexes through an Isolated Heterobimetallic Oxo Intermediate

“…The structure of 2 features distorted square‐planar geometries at each cobalt atom, with Co−O bond lengths similar to those in reported bis(μ‐oxo)dicobalt(III) complexes (1.769(1)–1.832(5) Å),, including two diketiminate Co III 2 (μ‐O) 2 complexes (Figure ) . The Co−Co distance of 2.7389(4) Å is within error of the longest previously reported distance in a bis(μ‐oxo)dicobalt complex …”

Oxygen activation by mononuclear Mn, Co, and Ni centers in biology and synthetic complexes

“…58,59 Other structurally characterized [Co2(μ-O)2] 2+ complexes derived from reaction with O2 have featured bidentate β-diketiminato, 60 guanidinato, 61 or monodeprotonated ureayl ligands. 62 Hikichi et al have shown that dicobalt(III) bis(μ-oxo) intermediates are potent oxidants capable of hydroxylating the isopropyl substituents of the Tp ligand. 59,63,64 Mononuclear peroxocobalt(III) complexes have been prepared by one of two routes: (1) direct reaction of Co(I) centers with O2 or 2 (12;Fig.…”