15823-71-9

The gas-phase reactions of ammonia with M(EN-(py)2) 2+, M(en)(phen)2+, and M(phen)22+, where M is Mn-(II), Fe(II), Co(II), Ni(II), Cu(II), or Zn(II), EN-(py) 2 is l,6-bis(2- pyridyl)-2,5-triazahexane, en is ethylene-diamine, and phen is 1,10-phenanthroline, have been studied in a quadrupole ion trap mass spectrometer. The trends in reactivity as a function of the metal are noticeably different for each complex despite the similarity of the ligand donor groups. These results indicate that coordination geometry and electronic structure have a significant impact on the gas-phase reactivity of four-coordinate metal complex ions. Specifically, for M(EN-(py) 2)2+ the equilibrium constants for the reactions with ammonia follow the trend Mn ≈ Fe ≈ Co > Zn ? Cu > Ni. The trend for the equilibrium constants of the M(en)(phen)2+ complexes is Mn ≈ Co ? Ni > Cu > Zn, and for the M(phen)22+ complexes, the trend is Ni > Mn ≈ Fe > Co > Cu > Zn. The most notable changes in reaction equilibrium constants occur for the Ni and Zn complexes, which increase and decrease, respectively, as the ligands are changed from EN-(py)2 to (en)(phen) to (phen)2. Molecular orbital stabilization energy (MOSE) and density functional theory (DFT) calculations are used to explain the experimental trends. Calculations indicate that the changes in reactivity observed for the Ni complexes are a result of different complex geometries; Ni(EN-(py)2)2+ is a low-spin square-planar complex, and Ni(phen)22+ is a high- spin tetrahedral complex. The decreased reactivity of the Zn complexes is due to the formation of a less distorted tetrahedral complex upon going from Zn(EN-(py)2)2+ to Zn(phen)22+. In addition, calculations show that the reactivities of the Mn, Fe, and Co complexes are consistent with slightly distorted tetrahedral structures, and the reactivities of the Cu complexes indicate that the complexes of this metal are close to square planar.

The mechanism of the Ullmann-type reaction between potassium thioacetate (KSAc) and iodobenzene (PhI) catalyzed by CuI associated with 1,10-phenanthroline (phen) as a ligand was explored experimentally and computationally. The study on C-S bond formation was investigated by UV-visible spectrophotometry, cyclic voltammetry, mass spectrometry, and products assessment from radical probes. The results indicate that under experimental conditions the catalytically active species is [Cu(phen)(SAc)] regardless of the copper source. An examination of the aryl halide activation mechanism using radical probes was undertaken. No evidence of the presence of radical species was found during the reaction process, which is consistent with an oxidative addition cross-coupling pathway. The different reaction pathways leading to the experimentally observed reaction products were studied by DFT calculation. The oxidative addition-reductive elimination mechanism via an unstable CuIII intermediate is energetically more feasible than other possible mechanisms such as single electron transfer, halogen atom transfer, and σ-bond methatesis.

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Investigations of the reaction of the bis(1,10-phenanthroline)copper(I) ion, Cu(phen)2+, with hydrogen peroxide in the presence of a scavenger (RH=methanol, ethanol, 2-propanol, or formate ion) and of the reactions initiated by radiation-produced hydroxyl free radical, OH., in similar systems in the absence of H2O2 show OH. is not formed by the Cu(phen)2+ + H2O2 reaction.The observed kinetics and stoichiometry of this reaction are interpreted in terms of a mechanism involving an intermediate, possibly a Cu-H2O2 complex, formed by reaction of Cu(phen)2+ with H2O2.The rate constant for the reaction of this intermediate with RH is smaller, by a factor of at least 1E4, than that for the reaction of OH. with RH.

By using the technique of pulse radiolysis to generate O2-, it is demonstrated that copper 1,10-phenanthroline ((op)2Cu2+) is capable to catalytically dismutating O2- with a turnover rate constant kcat. = (5.1 +/- 0.9)*108 M-1 s-1.The rate constants of the reduction of (op)2Cu2+ and of the oxidation of (op)2Cu+ by O2- have been determined to be (1.93 +/- 0.07)*109 and (2.95 +/- 0.3)*108 M-1 s-1, respectively.The kinetic results of the oxidation of (op)2Cu+ by molecular oxygen in aqueous solution are interpreted by a mechanism that proceeds via a superoxide intermediate, and the rate constant k-10 = (5.0 +/- 0.3)*104 M-1 s-1 has been determined.The rate constant of the oxidation of (op)2Cu+ by H2O2 was measured to be k22 = (937 +/- 20) M-1 s-1.

CuII precursors ligated to phenanthrolines are reduced in situ by alcohols or amines in the presence of a base (Cs2CO3) to generate CuI species which are active catalysts in C-N and C-O cross-coupling reactions. The conversion CuII → CuI has been evidenced and monitored by UV-vis and NMR spectroscopy.

Using the high-pressure pulse radiolysis technique, we have shown that the oxidation of (phen)2CuI (phen = 1,10-phenanthroline) by molecular oxygen proceeds via a transient in which a copper-oxygen bond is formed, i. e., via CuI-O2 a

It was established that complex compounds of copper(I) are capable of highly selective catalysis of the oxidation of alcohols to aldehydes by molecular oxygen in anhydrous alkaline media. It was found that n-propanol and benzyl alcohol are oxidized to propionaldehyde and benzaldehyde, respectively, in the presence of phenanthroline complexes of univalent copper and alkali at exceptionally high rates. It was shown that the formation of aldehydes occurs in the interaction of alcoholate ions, coordinated in the sphere of the Cu(I) complexes, with molecular oxygen.

The kinetics of the Co(acac)3 and Co(EDTA)- oxidations of Cu(PhCn)2+ have been investigated in both aqueous and micellar sodium dodecyl sulfate solution. Rate data indicate that the bis-chelated form of Cu(I) is the only reducing species in aqueous solution. The reaction rate is first order in both oxidant and reductant and reaches a limiting value at high phenanthroline concentrations. The following rate parameters have been obtained at pH 6 (cacodylate, μ = 0.25 M, excess phenanthroline): for Co(acac)3, k2 = 756 ± 2 M-1 s-1, ΔH? = 8.0 ± 0.5 kcal/mol, ΔS? = -19 ± 1 eu; for Co(EDTA)-, k2 = 448 ± 1 M-1 s-1, ΔH? = 7.5 ± 0.5 kcal/mol, ΔS? = -21 ± 1 eu. In 0.1 M SDS solution both the mono- and bis(phenanthroline) forms of Cu(I) are reducing species. The latter complex binds strongly to SDS micelles, resulting in 39- and 272-fold rate inhibitions for the Co(acac)3 and Co(EDTA)- oxidations, respectively. Barriers to electron transfer arising from strong micellar association of the reductant are calculated for both oxidations.

The proton-ligand formation constants of HL, formation constants of the binary complexes + and , and formation constants of the ternary complexes +, where A = 2,2'-bipyridyl, 1,10-phenanthroline, 2-(2'-pyridyl)benzimidazole, or 2-(2'-pyridyl)imidazole, and L = salicylamide ion, salicylanilide ion, 5-bromosalicylamide ion, or 5-bromosalicylanilide ion have been determined in dioxan-water (1 : 1, v/v) solutions, and 0.2 moldm-3 Na, at 30 deg C.The mixed-ligand stability constants KCuAL', for the reaction 2+ + L- +, have been calculated by three methods, namely, graphical linear plot, computer calculations considering complete formation of 2+ prior to the formation of +, and also considering all possible species to be present in solution.The values so obtained are very similar and the concentration plot confirms that the major species present in the solution are only 2+ and +.The value of Δ log K = log KCuAL' - logCuL is positive, except when A is 2-(2'-pyridyl)imidazoline.The majority of the mixed-ligand complexes have been synthesized and characterized.Electronic spectra confirm that there is no significant interaction between the two ligands through the metal d? orbitals in the mixed-ligand complexes.The greater stability of the ternary complexes may be due to a lowering of repulsion between metal d? electrons and the ligand electrons in these compounds.