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Abstract : Three cyclic thioesters of the formula ' $$-\hbox {SCH}_{2}\hbox {CH}_{2}\hbox {SCO}(\hbox {CH}_{2})_{\mathrm{n}}-$$ ' ( $$\mathbf{L}_{\mathbf{1}}, \hbox {n} = 0; \mathbf{L}_{\mathbf{2}}, = 1, \mathbf{L}_{\mathbf{3}}, \hbox {n} = 2$$ ) and their reactions with $$\hbox {Fe}_{3}(\hbox {CO})_{12}$$ are reported. All the reactions produced a known diiron complex, [ $$\hbox {Fe}_{2}(\upmu \hbox {-}\hbox {S}_{2}\hbox {C}_{2}\hbox {H}_{4})(\hbox {CO})_{6}$$ ] ( 1), which suggested that in the reactions, cleavage of C-S bond to generate ' $$\hbox {SCH}_{2}\hbox {CH}_{2}\hbox {S}$$ ' fragment is a common pathway for all the three ligands. In the case of ligand $$\mathbf{L}_{\mathbf{2}}$$ , a new complex 2, [ $$\hbox {Fe}_{2}\{\upmu \hbox {-}\hbox {SC}_{2}\hbox {H}_{4}(\hbox {SCH}_{2})\hbox {-}\upkappa \}(\hbox {CO})_{6}$$ ] was isolated and structurally characterized. In the reaction of ligand $$\mathbf{L}_{\mathbf{3}}$$ , an unknown iron carbonyl product was isolated in addition to complex 1. Although its precise structure was not established due to its instability and low yield, its infrared spectrum and decomposing into complex 1 implied that the product may be a cluster with higher nuclearity. The experimental observations suggested that with the increase of the ring size of the cyclic thioester ligands, further bond cleavages were involved in the reaction in addition to that leading to complex 1. GRAPHICAL ABSTRACT: SYNOPSIS Reaction of cyclic thioester ligands with triiron dodecacarbonyl leads to scission of C-S (C) bond which is initiated by the coordination of the S atom to the Fe atom. The larger the ring size of the ligand, the more diverse are the bond cleavages. [ABSTRACT FROM AUTHOR]

Four copper(ii) complexes with multidentate ligands, 1 ([CuL1Cl2]), 2 ([Cu(HL2)Cl2]), 3 ([Cu2(L2)2](ClO4)2) and 4 ([CuL3(HOCH3)ClO4]) {L1 = N,N-bis((pyridin-2-yl)methyl) prop-2-yn-1-amine, HL2 = 2-((((1-methyl-1H-imidazol-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenol and HL3 = 2-((((1-methyl-1H-imidazol-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)-2-t-butyl-phenol} are reported. The complexes were characterized by UV–vis spectroscopy, elemental analysis and electrochemical analysis. Complexes 1 and 3 were further characterized by X-ray single crystal diffraction analysis. The catalytic performances of these complexes were evaluated in the direct hydroxylation of benzene to phenol with hydrogen peroxide as an oxidant in aqueous acetonitrile media. Under optimized reaction conditions, complex 4 with the most negative reduction potential exhibited the highest conversion without considering the dinuclear complex 3. A correlation between the catalytic efficiency and the reduction potentials of these complexes was observed, that is the more negative the reduction potential, the higher the benzene conversion. A radical mechanism for the catalysis was confirmed by the fact that addition of radical scavengers such as TEMPO into the reaction mixture could severely suppress the catalysis. [ABSTRACT FROM AUTHOR]

Two multidentate ligands 2,2′-(1,1′-(pyridine-2,6-diylbis(methylene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene)bis((pyridin-2-ylmethyl)azanediyl)bis(methylene)diphenol ( H 2 L I ) and N , N ′-((1,1′-(pyridine-2,6-diylbis(methylene))bis(1H-1,2,3-triazole-4,1-diyl))bis(methylene))bis(1-(pyridin-2-yl)- N -(pyridin-2-ylmethyl)methanamine) ( L II ) containing triazolyl, phenolate and pyridinyl groups were prepared by click reaction between diazide and terminal alkynes in the presence of catalyst CuI. Both ligands were reacted with Cu 2+ and Fe 3+ salts to give three dinuclear complexes [ L I Cu 2 ](BPh 4 ) 2 ·2DMF ( 1 ), [ L II (DMF) 2 Cu 2 ](ClO 4 ) 4 ·H 2 O ( 2 ) and [ L II (FeCl 2 ) 2 ](PF 6 ) 2 ( 3 ). All complexes were characterized by IR, UV–Vis spectra and element analysis. X-ray analysis revealed that the Cu 2+ centers in complexes 1 and 2 adopted the distorted trigonal bipyramidal geometry, and the Fe 3+ center in complex 3 chose an octahedral geometry. In addition, the electrochemistry of complexes 1 – 3 was investigated. [ABSTRACT FROM AUTHOR]

Metallacyclic complex [(Me2N)3Ta(η2-CH2SiMe2NSiMe3)] ( 3) undergoes CH activation in its reaction with H3SiPh to afford a Ta/μ-alkylidene/hydride complex, [(Me2N)2{(Me3Si)2N}Ta(μ-H)2(μ-C-η2-CHSiMe2NSiMe3)Ta(NMe2)2] ( 4). Deuterium-labeling studies with [D3]SiPh show H-D exchange between the Ta DTa unit and all methyl groups in [(Me2N)2{(Me3Si)2N}Ta(μ-D)2(μ-C-η2-CHSiMe2NSiMe3)Ta(NMe2)2] ([D2]- 4) to give the partially deuterated complex [D n]- 4. In addition, 4 undergoes β-H abstraction between a hydride and an NMe2 ligand and forms a new complex [(Me2N){(Me3Si)2N}Ta(μ-H)(μ-N-η2-C,N-CH2NMe)(μ-C-η2-C,N-CHSiMe2NSiMe3)Ta(NMe2)2] ( 5) with a cyclometalated, η2-imine ligand. These results indicate that there are two simultaneous processes in [D n]- 4: 1) H-D exchange through σ-bond metathesis, and 2) HD elimination through β-H abstraction (to give [D n]- 5). Both 4 and 5 have been characterized by single-crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

Abstract: Treatment of the pentadentate macrocyclic ligand 4-(pyridin-2-ylmethyl)-1,7-dithia-4,10-diazacyclododecane, L, and the hexadentate macrocyclic ligand 4,10-bis(pyridin-2-ylmethyl)-1,7-dithia-4,10-diazacyclododecane, L′, with one equivalent of a M2+ metal salt (M=Co, Ni, Cu) in methanol yielded six mononuclear complexes, [CoL(MeCN)](ClO4)2 (1), [NiL(H2O)]Cl2 (2), [CuL(MeCN)](ClO4)2 (3) and [ML′](ClO4)2 (4–6). Their solid state crystal structures were determined using X-ray single crystal diffraction analysis. In complexes 1–3, the metal centres exhibit a slightly distorted octahedral geometry, resulting from the coordination of three nitrogen and two sulfur donating atoms in the ligand L and one solvent molecule (MeCN for complexes 1 and 3, water for complex 2) whereas in complexes 4–6, the coordination around the metal centres was satisfied by four nitrogen and two sulfur atoms from the ligand L′. The electronic spectra and electrochemistry of these complexes are reported. [Copyright &y& Elsevier]

Abstract: A novel hexadentate ligand, N-(pyridin-2-ylmethyl)-N,N′-(bis-(2-(pyridin-2-ylmethylthio))ethyethanamine) (L), containing “N4S2” donor-set was synthesized. Its reaction with one equivalent of divalent metal perchlorate salts, M(ClO4)2·6H2O (M=Zn, Cu, and Co), in methanol yielded three mononuclear complexes [ML](ClO4)2 (M=Zn, 1; Cu, 2; Co, 3) in octahedral geometry. The complexes were fully characterized and their structures were determined using X-ray single crystal diffraction analysis. UV–Vis spectra of the complexes revealed that metal-to-ligand charge transfer (MLCT) transition bands showed readily red-shift in the trend of Zn(II), Co(II), and Cu(II) complexes. Upon the divalent metal binding, the ligand-based reduction process shifted positively which, otherwise, is not observable in the electrochemical window. [Copyright &y& Elsevier]

Abstract: Reaction of chlorotrisulfidomolybdate [PPh4][MoClS3] (1) with one equivalent of tridentate ligand PyCH2NHC2H4SNa (PyNSNa) in THF generated both a mononuclear and a dinuclear complexes, [PPh4][(PyNS)MoO(η 2-S2)2] (2) and [PPh4][(PyNS)Mo(O)(μ-S)2Mo(S)(η 2-S2)]·0.5MeCN (3·0.5MeCN). These two complexes were separated mechanically and fully characterized using IR, UV/Vis spectra, 1H NMR spectra and X-ray single crystal diffraction analysis. In both complexes, one terminal sulfido ligand was substituted by one oxo group. In complex 3, two types of intermolecular hydrogen bonding in its solid state led to a 1-D structure in which each unit was a dimmer formed via hydrogen bonding. [Copyright &y& Elsevier]

Five tetradentate ligands, L 1 – 5 , bearing the moiety of bis(pyridin-2-ylmethyl)amine ( 1 ) and their complexes with Mn(II) were prepared. All the compounds and metal complexes were appropriately characterized. The five manganese(II) complexes ( 3a–e ) are of the formula, [Mn(II) L x Cl 2 ] (x = 1-5), as suggested by the crystal structure of complexes 3b and 3c . All the ligands except for L 3 possess two iodobenzene groups via an ether linkage (except for L 1 ) with various lengths. By using oxone as an oxidant, the catalytic activity of these complexes on the oxidation of ethylbenzene to acetophenone in acetonitrile/water at room temperature was studied. Our results showed that the pendant iodophenyl groups play a synergetic role with the metal center in the catalysis, and complex 3b possesses the most appropriate length of the linkage between the iodobenzene group and the metal center. EPR and FTIR data suggest that the metal center of the active species should be Mn(IV) after the oxidation of oxone under the reaction conditions. A catalytic mechanism was also proposed based on the experimental observations. [ABSTRACT FROM AUTHOR]

Abstract: Two Hg(II) complexes [HgL′(ClO4)2] (1) and [HgL(ClO4)]ClO4 (2) derived from the macrocyclic ligands, 4-(pyridin-2-ylmethyl)-1,7-dithia-4,10-diazacyclododecane (L′) and 7-(pyridin-2-ylmethyl)-1,4,10-trithia-7,13-diazacyclopentadecane (L), have been crystallographically characterised. Ligand L and its Hg(II) complex were isolated unexpectedly, and a possible formation pathway of the ligand is proposed. By including weakly bound O atoms from the perchlorate ions, the Hg atoms in both complexes are seven-coordinate and possess capped trigonal prismatic geometries. These uncommon structures for Hg(II) complexes were achieved mainly by the relatively large size of the metal ion and the steric effect from the macrocycles. In both complexes, strong hydrogen bonding between the amine hydrogen atom and a perchlorate ion was observed. For complex 1, the interaction is N(3)–H(15)···O(8) at 2.08(12)Å where O(8) is of the same anion as one of the coordinated O atoms; in complex 2, a similar hydrogen bond, N(7)–H(7)···O(32), with a distance of 2.25Å, is formed to the coordinated anion, but the second anion remains discrete. [ABSTRACT FROM AUTHOR]