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Abstract We disclose a novel boron trifluoride induced C–H activation and difluoroboronation at room temperature, thus providing a straightforward gateway to a series of N,O-bidentate organic BF2 complexes. The scope of the method is demonstrated with 24 examples. All the synthesized compounds exhibit fluorescence and some of them have large Stokes shifts. Graphical Abstract

A base-induced synthesis of 2-(4-(2-(phenylthio)ethyl)piperazinyl) acetonitriles by reaction of disulfides, 1-(chloromethyl)-4-aza-1-azonia bicyclo[2.2.2]octane chloride and trimethylsilyl cyanide is reported. The scope of the method is demonstrated with 30 examples. The reaction mechanism research indicates that the three-component reaction would be a SN2 reaction. The products exhibit good activities towards advanced synthesis of aqueous soluble acyl-CoA: cholesterol O-acyltransferase-1 (ACAT-1) inhibitors. Our work is superior as it uses less-odor disulfides as carbon sources and EtOH as solvent in a water and dioxygen insensitive reaction system, followed by a simple purification process.

A simple and efficient method for the synthesis of dialdehyde aniline in good yields (up to 83%) is explored using Cu(OTf)2 as the catalyst, Selectfluor as the radical initiator, and DMSO as both the carbon and oxygen sources. Experimental studies indicate that the reaction is achieved by the formylation of two CAr-H bonds, first at the para-position and then at the ortho-position. A possible mechanism is proposed, including the thermal homolysis of Selectfluor, the Cu(II)-facilitated formylation of the CAr-H bonds, and the hydrolysis of the amide under alkaline conditions in air atmosphere.

A simple and efficient method is explored for the synthesis of 2-hydroxyimino-2-phenylacetonitriles (2) and phthalimides (4), by using nitromethane as nitrogen donors. Both reactions are promoted by Cu(II) system with the participation of dioxygen as an oxidant. The scope of the method has been successfully demonstrated with a total of 51 examples. The flexible and diversified characteristics of reactions are introduced in terms of electronic effect, steric effect, position of substituted groups, and intramolecular charge transfer. Experimental studies suggest that the methyl nitrite could be a precursor in the path to the final products. A possible reaction mechanism is proposed, including the Cu(II)/O2-facilitated transformation of nitromethane to methyl nitrite, the base-induced formation of 2-hydroxyimino-2-phenylacetonitriles, and the base-dioxygen-promoted formation of phthalimides.

A structure similar to the singular feature of the catalytic C-cluster of carbon monoxide dehydrogenase, a sulfide-bridged Ni-Fe locus where substrate is bound and transformed in the reversible reaction, is described. The synthesis and reactivity of [Ni.sup.II][Fe.sup.II] complexes have shown that molecular [Ni.sup.II]-[Fe.sup.II] sites and bridges are attained, which is a necessity in the biomimetic chemistry of C-clusters.

Research has been conducted on terephthalic acid, salicylidene alkylimine, NaOH and inorganic manganese(II) or (III) salt. Results demonstrate that the reaction system consisting of these compounds produses dinuclear manganese complexes.

The planar NNN-pincer complexes [MII(pyN₂Me2)(OH)](MII = Ni, Cu) fix CO₂ in η₁ OCO₂H complexes; results for the copper system are described. MnII, FeII, CoII, and Znn behave differendy, forming [MII(pyN₂Me2)₂]2- with N₄O₂ coordination. Incorporation of the Ni11 pincer into binucleating macrocycle 2 containing a triamino Mn locus connected by two 13-biphenylene groups affords proximal NiII and MII sites for investigation of the synthesis, structure, and reactivity of Ni--X--M bridge units. This ligand structure is taken as a reference for variations in Mn atoms and binding sites and bridges X = OH⁻ and CN⁻ to produce additional members of the macrocyclic family with improved properties. Macrocycle 2 with a 22-membered ring is shown to bind MII = Mn, Fe, and Cu with hydroxo bridges. Introduction of the 4-Bu'O group (macrocycle 3) improves the solubility of neutral complexes such as those with NiII--OH--CuII and NiII--CN--FeII bridges. Syntheses of macrocycle 5 with a 7-Me-[l2]aneSN3 and macrocycle 6 with a l,8-Me₂-[l4]aneN₄ MII binding site are described together with hydoxo-bridged Ni/Cu and cyano-bridged Ni/Fe complexes. This work was motivated by the presence of a Ni...(HO)--Fe bridge grouping in a reactive state of carbon monoxide dehydrogenase. Attempted decrease in Ni--(OH)--M distances (3.70--3.87 Å) to smaller values observed in the enzyme by use of macrocycle 4 having 1,2-biphenylene connectors led to a mononuclear octahedral NiII complex. Bridge structural units are summarized, and the structures of 14 macrocyclic complexes including 8 with bridges are described. [ABSTRACT FROM AUTHOR]

Carbon dioxide may react with free or metal-bound hydroxide to afford products containing bicarbonate or carbonate, often captured as ligands bridging two or three metal sites. We report the kinetics and probable mechanism of an extremely rapid fixation reaction mediated by a planar nickel complex [NiII(NNN)(OH)]1- containing a tridentate 2,6-pyridinedicarboxamidate pincer ligand and a terminal hydroxide ligand. The minimal generalized reaction is M-OH + CO2 → M-OCO2H; with variant M, previous rate constants are ≲10³ M-1 s-1 in aqueous solution. For the present bimolecular reaction, the (extrapolated) rate constant is 9.5 × 105 M-1 s-1 in N, N'-dimethylformamide at 298 K, a value within the range of kcat/KM≈105-108 M-1 s-1 for carbonic anhydrase, the most efficient catalyst of CO2 fixation reactions. The enthalpy profile of the fixation reaction was calculated by density functional theory. The initial event is the formation of a weak precursor complex between the Ni-OH group and CO2, followed by insertion of a CO2 oxygen atom into the Ni-OH bond to generate a four center Ni(η²-OCO2H) transition state similar to that at the zinc site in carbonic anhydrase. Thereafter, the Ni-OH bond detaches to afford the Ni(η¹-OCO2H) fragment, after which the molecule passes through a second, lower energy transition state as the bicarbonate ligand rearranges to a conformation very similar to that in the crystalline product. Theoretical values of metric parameters and activation enthalpy are in good agreement with experimental values [ΔH‡ = 3.2(5) kcal/mol]. [ABSTRACT FROM AUTHOR]

A singular feature of the catalytic C-cluster of carbon monoxide dehydrogenase is a sulfide-bridged Ni⋯Fe locus where substrate is bound and transformed in the reversible reaction CO + H2O ⇌ CO2 + 2H+ + 2e-. A similar structure has been sought in this work. Mononuclear planar NiII complexes [Ni(pyN2Me2)L]1- (pyN2Me2 = bis(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate(2-)) derived from a NNN pincer ligand have been prepared including L = OH- (1) and CN- (7). Complex 1 reacts with ethyl formate and CO2 to form unidentate L = HCO2 (5) and HCO3 (6) products. A binucleating macrocycle was prepared which specifically binds NiII at a NNN pincer site and five-coordinate FeII at a triamine site. The NiII macrocyle forms hydroxo (14) and cyanide complexes (15) analogous to 1 and 7. Reaction of 14 with FeCI2 alone and with ethyl formate and 15 with FeCI2 affords molecules with the NiII-L-FeII bridge unit in which L = μ2:η1-OH (17) and μ2:η1-HCO2- (18) and -CN- (19). All bridges are nonlinear (17, 140.0°; 18, M-O-C 135.9° (Ni), 120.2° (Fe); 19, Ni-C-N 170.3°, Fe-N-C 141 .8°) with NiII⋯FeII separations of 3.7-4.8 Å. The NiIIFeII complexes, lacking appropriate Ni-Fe-S cluster structures, are not site analogues, but their synthesis and reactivity provide the first demonstration that molecular NiII⋯FeII sites and bridges can be attained, a necessity in the biomimetic chemistry of C-clusters. [ABSTRACT FROM AUTHOR]

Pyridine-2,6-dimethanethiolate and pyridine-2,6-dithiocarboxylate form sparingly soluble Ni[supII] pincer complexes formulated as [Ni(pdmt)][sub2] and Ni(pdtc)][sub2], respectively, with Ni-(μ[sub2]-S)-Ni bridges. In acetonitrile reaction systems, the latter undergoes the facile bridge cleavage reactions [Ni(pdtc)][sub2] + 2L[sup0,-]→2[Ni(pdtc)L][sup0,-] with an extensive set of nucleophiles to afford planar mononuclear products with L[sup-] = halide, CN, Me[sub3]SiO[sup-], RS[sup-] and L[sup0] = Et[sub3]P and a N-heterocyclic carbene. [Ni(pdmt)][sub2] is considerably less reactive toward bridge disruption. Cleavage products support several reactions of interest leading to other mononuclear species and to di and trinuclear complexes. [Ni(pdtc)(OSiMe[sub3])][sup1-] deprotonates acetonitrile and acetone to form [Ni(pdtc)(CH[sub2]R)][sup1-] (R=CN, COMe). Reaction of [Ni(pdtc)SEt][sup1-] with Fe[supII] yields the thiolate-bridged dimer ([Ni(pdtc)][sub2](SEt))[sup1-]. Refluxing an acetonitrile solution of [Ni(pctd)SH][sup1-] in air results in trinuclear [Ni(pdtc)][sub3]S][sup2-] containing the rare unsupported Ni[sub3](μ[sub3]-S) bridge core. Reaction of [Ni(pdtc)CN][sup1-] with [Fe(Me[sub6]tren)(OTf)][sup1+] forms the complex [Ni(pdtc)CNFe(Me[sub6]tren)][sup1+], the only example of a single Ni—CN— Fe bridge within a molecule. Structures of the various types of reaction products are presented. This work demonstrates the potential utility of bridge cleavage of polynuclear Ni[supII] thiolates, an extensive family of compounds to produce mononuclear products. [ABSTRACT FROM AUTHOR]

Aggregation of tetranuclear Mn4O2 building blocks with alkali ion was studied. Several Mn(iii) complexes containing [Mn4O2(AcO)7(pyz)2]− (pyz = pyrazinate) anion(s) were obtained from an assembly system containing Mn(ii), MnO4−, HOAc and Hpyz (Napyz or Kpyz). These [Mn4O2]8+ complexes have monomeric (1 and 2), dimeric (4 and 5) and one-dimensional chain (3) structures of which alkali metal ion connects the Mn ions of adjacent [Mn4O2]8+ units through µ1,1- and µ1,3-carboxylate bridges. Complexes 2 or 3 were converted into [Mn12O12(AcO)16(H2O)4] in EtOH solution in the presence of HOAc. However, in MeOH solution, a coordination polymer [Mn2(HCOO)4(H2O)4]n was obtained accompanying the oxidation of MeOH to become HCHO and HCOOH. Tracing the 1H NMR spectra of 2 or 3 in CD3OD, the disappearance of the resonance signals in 3 h indicated the decomposition of the [Mn4O2]8+ cores. Complex 2 exhibits its proton NMR signals in CDCl3 which are similar to those of its pic analogue but accompany downfield shift to various extents for all the corresponding signals. Variable-temperature magnetic susceptibilities of complexes 2–5 in the range 5–300 K were recorded and were fitted for an Mn4O2 butterfly core, giving the fitting parameters Jbb = −2.67 to −3.76 cm−1 and Jwb = −1.16 to −3.14 cm−1. Small J values indicate weak antiferromagnetic coupling interactions of the Mn(iii) sites and the spin ground states are considered as ST = 0 based on the Jbb/Jwb ratio ≈1 for these complexes. The ESR spectra were recorded for complex 2 in dual-mode at liquid-helium temperatures and no obvious signal could be found. The addition of p-cresol gives rise to the reduction of the [Mn4O2]8+, resulting in observable signals. [ABSTRACT FROM AUTHOR]

The water-oxidizing complex (WOC) within photosystem II (PSII) can be reconstituted with synthetic manganese complexes by a process called photoactivation; however, the key factors affecting the efficiency of synthetic manganese complexes in reconstitution of electron transport and oxygen evolution activity in manganese-depleted PSII remain unclear. In the present study, four complexes with different manganese coordination environments were used to reconstitute the WOC, and an interesting relationship was found between the coordination environment of the manganese atom in the complexes and their efficiency in restoring electron transport and oxygen evolution. If Mn(II) is coordinated to nitrogen atoms within the ligand, it can restore significant rates of electron transport and oxygen evolution; however, if the manganese atom is coordinated only to oxygen atoms instead of nitrogen atoms, it has no capability to restore electron transport and oxygen evolution. So, our results demonstrate that the capability of manganese complexes to reconstitute the WOC is mainly determined by the coordination between nitrogen atoms from ligands and the manganese atom. It is suggested from our results that the ligation between the nitrogen atom and the manganese atom within the manganese complex facilitates the photoligation of the manganese atom to histidyl residues on the apo-protein in manganese-depleted PSII during photoactivation. [ABSTRACT FROM AUTHOR]

A reaction system consisting of terephthalic acid, NaOH, inorganic Mn(II) or Mn(III) salt, and salicylidene alkylimine resulted in dinuclear manganese complexes (salpn)[sub 2]Mn[sub 2](µ-phth)(CH[sub 3]OH)[sub 2] (1, salpn = N,N'-l,3-propylenebis(salicylideneiminato); phth = terephthalate dianion), (salen)[sub 2]Mn[sub 2](µ-phth)(CH[sub 3]OH)[sub 2] (2, salen = N,N'-ethylenebis(salicylideneiminato)), (salen)[sub 2]Mn[sub 2](µ-phth)(CH[sub 3]OH)(H[sub 2]O) (3), and (salen)[sub 2]Mn[sub 2](µ-phth) (4), while the absence of NaOH in the reaction led to a mononuclear Mn complex (salph)Mn(CH[sub 3]OH)(NO[sub 3]) (5, salph = N,N'-1,2-phenylenebis(salicylideneiminato)). In addition, a trinuclear mixed metal complex H{Mn[sub 2]Na(salpn)[sub 2](µ-OAc)[sub 2](H[sub 2]O)[sub 2]}(OAc)[sub 2] (6) was obtained from the reaction system by using maleic acid instead of terephthalic acid. Five-coordinate Mn ions were found in 4 giving rise to an intermolecular interaction and constructing a one-dimensional linear structure. Antiferromagnetic exchange interactions were observed for 1-3, and a total ferromagnetic exchange of 4 was considered to stem from intermolecular magnetic coupling. ¹H NMR signals of phenolate ring and alkylene (or phenylene) backbone of the diamine are similar to those reported in the literature, and the phth protons are at -2.3 to -10.1 ppm. Studies on structure, bond valence sum analysis, and magnetic properties indicate the oxidation states of the Mn ions in 6 to be +3, which are also indicated by ESR spectra in dual mode. Ferromagnetic exchange interaction between the Mn(III) sites was observed with J = 1.74 cm[sup -1]. A quasireversible redox pair at -0.29V/0.12V has been assigned to the redox of Mn[sub 2](III)/Mn(III)Mn(II), implying the intactness of the complex backbone in solution. [ABSTRACT FROM AUTHOR]

The structure of [Ag([18]aneS4O2)](PF6)2·CH2Cl2 shows a highly unusual and unexpected boat conformation for the macrocycle with square-planar S4-coordination at the formal Ag(ii) centre and the two ether O-centres lying on the same side of the S4 plane; the SOMO in [Ag([18]aneS4O2)]2+ possesses 22.7% Ag 4dxy character, as determined by multi-frequency EPR spectroscopy and supported by DFT calculations. [ABSTRACT FROM AUTHOR]

Discusses the crystal structure of catena-Poly[[[(1, 10-phenanthroline-κ²N,N')manganese(II)]-u-L-tartrato-κ[s up 4]O¹,O²:O[sup 3],O[sup 4]] hexahydrate]. Hydrogen-bonding geometry; Distortion of the octahedral coordination environment.