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Catalytic oxidation of tricyclic endo-norbornene-fused tetrahydrofuran with the bimetallic nanocluster Cu/Au-PVP in the presence of H2O2 or t-BuOOH as the oxidant leads to C–H bond oxidation adjacent to the ether function to give 4-oxa-tricyclo[5.2.1.0]-8,9-exo-epoxydecane, however, oxidation with Pd/Au-PVP takes place at the C=C double bond to give the same epoxide and the oxidative three-bond forming dimeric product, dodecahydro-1,4:6,9-dimethanodibenzofurano[2,3-b:7,8-b′]bisoxolane. Formation of the latter product suggests the involvement of a reactive Pd–C intermediate. Similarly, oxidative C–C bond-forming reactions are observed in cycloaddition reactions of N2-Boc-1,2,3,4-tetrahydro-γ-carbolines and 2,3-dihydroxybenzoic acid with Cu/Au-PVP (2–5 mol%) and H2O2 at 25 °C, providing two-bond-forming [4+2] cycloadducts. Under similar reaction conditions, Pd/Au-PVP did not produce the corresponding cycloadduct, indicating a need for complexation between Cu and the carboxylic acid group of 2,3-dihydroxybenzoic acid and the allylic amine function of the γ-carbolines during the cyclization reaction. The reported intermolecular coupling reactions using Pd/Au-PVP or Cu/Au-PVP nanocluster catalysts under oxidative conditions at 25 °C are unprecedented.

 

While alkylperoxomanganese(iii) (MnIII–OOR) intermediates are proposed in the catalytic cycles of several manganese-dependent enzymes, their characterization has proven to be a challenge due to their inherent thermal instability. Fundamental understanding of the structural and electronic properties of these important intermediates is limited to a series of complexes with thiolate-containing N4S− ligands. These well-characterized complexes are metastable yet unreactive in the direct oxidation of organic substrates. Because the stability and reactivity of MnIII –OOR complexes are likely to be highly dependent on their local coordination environment, we have generated two new MnIII–OOR complexes using a new amide-containing N5− ligand. Using the 2-(bis((6-methylpyridin-2-yl)methyl)amino)- N-(quinolin-8-yl)acetamide (H6Medpaq) ligand, we generated the [MnIII(OO)tBu)(6Medpaq)]OTf and [MnIII(OOCm)(6Medpaq)]OTf complexes through reaction of their MnII or MnIII precursors with t BuOOH and CmOOH, respectively. Both of the new Mn III–OOR complexes are stable at room-temperature (t1/2 = 5 and 8 days, respectively, at 298 K in CH3CN) and capable of reacting directly with phosphine substrates. The stability of these MnIII–OOR adducts render them amenable for detailed characterization, including by X-ray crystallography for [MnIII (OOCm)(6Medpaq)]OTf. Thermal decomposition studies support a decay pathway of the MnIII–OOR complexes by O–O bond homolysis. In contrast, direct reaction of [MnIII(OOCm)(6Medpaq)] + with PPh3 provided evidence of heterolytic cleavage of the O–O bond. These studies reveal that both the stability and chemical reactivity of MnIII–OOR complexes can be tuned by the local coordination sphere. 

Manganese ([Mn(CO) 3 ]) and rhenium tricarbonyl ([Re(CO) 3 ]) complexes represent a workhorse family of compounds with applications in a variety of fields. Here, the coordination, structural, and electrochemical properties of a family of mono- and bimetallic [Mn(CO) 3 ] and [Re(CO) 3 ] complexes are explored. In particular, a novel heterobimetallic complex featuring both [Mn(CO) 3 ] and [Re(CO) 3 ] units supported by 2,2′-bipyrimidine (bpm) has been synthesized, structurally characterized, and compared to the analogous monomeric and homobimetallic complexes. To enable a comprehensive structural analysis for the series of complexes, we have carried out new single crystal X-ray diffraction studies of seven compounds: Re(CO) 3 Cl(bpm), anti -[{Re(CO 3 )Cl} 2 (bpm)], Mn(CO) 3 Br(bpz) (bpz = 2,2′-bipyrazine), Mn(CO) 3 Br(bpm), syn - and anti -[{Mn(CO 3 )Br} 2 (bpm)], and syn -[Mn(CO 3 )Br(bpm)Re(CO) 3 Br]. Electrochemical studies reveal that the bimetallic complexes are reduced at much more positive potentials (Δ E ≥ 380 mV) compared to their monometallic analogues. This redox behavior is consistent with introduction of the second tricarbonyl unit which inductively withdraws electron density from the bridging, redox-active bpm ligand, resulting in more positive reduction potentials. [Re(CO 3 )Cl] 2 (bpm) was reduced with cobaltocene; the electron paramagnetic resonance spectrum of the product exhibits an isotropic signal (near g = 2) characteristic of a ligand-centered bpm radical. Our findings highlight the facile synthesis as well as the structural characteristics and unique electrochemical behavior of this family of complexes. 

Structurally elusive inositol hexakisphosphates have been trapped in host–guest sandwiches between two picolinamide macrocycles that remain intact in solution, aided by hydrogen bonds and electrostatic interactions. This first report of macrocyclic complexes of inositol hexakisphosphates provides structural insight to significant biosources of phosphorus that impact the global phosphorus cycle.