Jorge Manzur

Oxidation of 3,5-ditert-butylcatechol catalyzed by copper(II) complexes. A kinetic study

Abstract Copper(II) complexes of the ligands (6-methyl-2,2′-dipridyl)methane (MeDPM) and (6,6′-dimethyl-2,2′-dipyridyl)methane (diMeDPM) were prepared and used as catalysts for the oxidation of 3,5-ditertbutylcatechol to 3,5-ditert-butyl-o-benzoquinone. The rate of reaction was determined in the presence and absence of base (KOH) in methanol. The kinetic data are interpretated, postulating two reactive species towards molecular oxygen: a copper(I) complex and a species described as a ternary copper(II) catecholate complex.

Carbon–hydrogen cleavage versus ring opening in the oxidative addition reactions of furan, thiophene, selenophene and tellurophene with [Os3(CO)10(MeCN)2]

Reactions of the cluster [Os3(CO)10(MeCN)2] with furan, thiophene, selenophene or tellurophene lead to compounds of corresponding stoichiometry, [Os3(CO)10(C4H4E)](E = O, S, Se or Te), but, whereas for E = O or S these are furyl or thienyl hydrido compounds formed by C–H cleavage, the Se and Te clusters are formed by E–C cleavage (X-ray structure for the E = Se cluster).

Ring opening and extrusion of tellurium atoms in the reaction of benzo[b]tellurophene with trinuclear iron, ruthenium and osmium clusters: X-ray crystal structures of [Os2(μ-C8H6Te)(CO)10], [Os4(μ-C8H4)(μ3-Te)(CO11], [Ru(μ-C8H6Te)(CO)6)], [Ru4(μ3-Te)(μ-C8H6)(CO)11] and [Fe2)μ-C8H6Te(CO)6]

Abstract The trinuclear carbonyl clusters [Fe3(CO)12], [Ru3(CO)12], [Os3(CO)12] and [Os3(CO)10(MeCN)2] react with benzo[b]tellurophene under mild conditions, in refluxing tetrahydrofuran, to give compounds containing the open-chain ligands C6H4CHCHTe or the fragments Te and C8H6 as bridging ligands. The following compounds were isolated and characterised: [Os3(μ-C8H6Te)(CO)10] (1), [Os2(μ-C8H6Te)(CO)6] [Os2(μ-C8H6)(CO)6] (3) [Os4μ-C8H6)(μ3-Te(CO)11] (4), which were obtained were obtained from the reaction of [Os3(CO)12] and benzo[b]tellurophene. [Ru3(μ-C8H6)(CO)8)] (5) (X-ray reported previously) [Ru2(μ-C8H6Te)(CO)6] (6), [Ru2(μ-C8H6] (7) and [Ru4(μ3-Te(μ-C8H6)(CO)11] (8) were derived from the reaction of [Ru3(CO)12] and benzo[b]tellurophene; [Fe2(μ-C8H6Te)(CO)6] (9) and [Fe2(μ-C8H6)(CO)6] (10) were obtained from [Fe3(CO)12]. All the compounds were characterised by 1H NMR and IR spectroscopy in solution and 1, 4, 6, 8 and 9 were characterised by X-ray diffraction methods in the solid state. All the clusters were shown to have had a TeC bond broken to give the C6H4CHCHTe as a bridging ligand linking two metal atoms. Cluster 8 was shown by single-crystal X-ray diffraction methods to have had both TeC bonds broken to give a μ3-Te ligand and a C8H6 bridging ligand. This cluster contains a Te-capped triangle of ruthenium atoms and there is a spiked ruthenium atom supporting the bridging C8H6 ligand. In this case the Te atom has been extruded from the heterocycle but remains in the cluster. Crystal data: 1: monoclinic, space group P2 1 /a, a=12.326(7), b=13.821(4), c=13.538(5) A , β=107.01(3)°, Z=4; 4: monoclinic, space group P2 1 /n, a=16.740(2), b=8.684(3), c=18.536(4) A , β=112.87(1)°, Z=4; 6: monoclinic, space group P2 1 /a, a=12.291(3), b=12.098(5), c=22.880(4) A , β=95.24(2)°, Z=8 ; 8: monoclinic, space group P2 1 /n, a=14.376(4), b=11.268(4), c=15.313(4) A , β=96.27(2)°, Z=4 ; 9: monoclinic, space group P2 1 /a, a=12.094(3), b=11.737(3), c=22.632(4)r A , β=96.66(2)°,Z=8 . The structures were solved by direct methods and were refined by full-matrix least-squares to R=0.0309, 0.0364, 0.0348, 0.0220 and 0.0410 for 4073, 3628, 3414, 2005 and 4985 reflections with I>3σ(I), respectively.

Oxidation of 3,5-di-tert-butylcatechol by molecular oxygen catalysed by a copper(I) complex, Cu2(bdpdz)Cl2, bdpdz=3,6-bis-(di-2-pyridilmethyl) pyridazine

Abstract The syntheses, voltammetry and autoxidation of the binuclear copper(I) complex, Cu 2 (bdpdz)Cl 2 , (bdpdz=3,6-bis-(di-2-pyridylmethyl)pyridazine) are reported. The complex catalyses the aerobic oxidation of 3,5-di- tert -butylcatechol, DTBCH 2 , to 3,5-di- tert -butyl- o -benzoquinone. At constant catalyst concentration (5×10 −5 M) the initial rate of oxygen uptake increases with increasing amounts of substrate reaching an asymptotic value. At constant DTBCH 2 (1×10 −3 M) the reaction rate depends linearly on the concentration of catalyst with a rate constant k ′ equal to 8.8×10 −3 s −1 . The relevance of the oxidation of DTBCH 2 by the copper(I)–dioxygen adduct becomes evident from the kinetic data reported in this work.

Magneto-structural characterization of [Cu4(prz)4(CH3OH)2L2″](ClO4)2 (L″H = 1,1-di-(2-pyridyl)-1-methoximethanol, PRZH = pyrazole)

Abstract The title compound [Cu2C19H20N6O7Cl]2 is a copper(II) complex, in which each bicationic moiety is bridged by two pyrazolate ligands. In the centrosymmetric, tetrameric dications pairs of copper atoms, one square planar and one square pyramidal, are bridged by an oxygen from the pyridylmethoxymethanol ligand and a pyrazolate moiety, with one example of five coordination completed by a methanol solvent molecule. These dimers are then bridged by two pyrazoles, to give the tetramer. Two perchlorate counter-anions are bound to the tetrameric unit by hydrogen bonds, which stabilize the crystal structure. The copper(II) complex presents antiferromagnetic behaviour with TM = 190 K. Supposing that the alkoxo oxygen bridge is the main pathway for the superexchange interaction, the experimental magnetic susceptibilities were fitted to the Bleaney-Bowers equation for dimers, yielding a 2J value of −211.2 cm−1.

Synthesis and magnetostructural characterization of dinuclear copper(II) complexes with the diazine ligand, 3,6-bis(di-2-pyridylmethyl)pyridazine

The crystal structures of [Cu2(bdpdz)Br4]·2CH3CN 1, [Cu2(bdpdz)Cl3(H2O)]Cl·3.5H2O 2 and [Cu2(bdpdz)2][ClO4]43 were determined by X-ray analysis, where bdpdz, represents the binucleating ligand 3,6-bis(di-2-pyridylmethyl)pyridazine, formed by the reaction of 3,6-dichloropyridazine and di-2-pyridylmethyllithium. Compounds 1 and 2 consist of discrete binuclear units, in which copper atoms are linked by the diazine bridge and two halide ions. The pyridazine acts as a hexadentate ligand. In complex 2 the two copper(II) ions have a distorted octahedral co-ordination geometry, 4 + 2. Compound 3 also consists of discrete binuclear units, in which the copper centres are linked by two organic ligands. Here bdpdz acts as a pentadentate ligand, with one of the diazine nitrogen atoms not bonded. The two copper(II) ions have a square pyramidal co-ordination geometry, 4 + 1. The magnetic susceptibility was investigated in the temperature range 300–5 K. These measurements reveal an antiferromagnetic interaction for all three compounds (–2J= 98.1 for 1, 79.6 for 2 and 6.4 cm–1 for 3). The lack of a diazine bridge, N–N, for the perchlorate salt 3 substantially reduces the antiferromagnetic interaction.

Ring opening versus phenyl–phosphorus bond cleavage in incorporating a phosphole into triosmium clusters

The five-membered heterocyclic compound 3,4-dimethyl-1-phenylphosphole (Ph[graphic omitted]H) reacts with [Os3(CO)11(MeCN)] or [Os3(CO)10(MeCN)2] to give the simple substitution products [Os3(CO)12–x(PhPC4H2Me2)x](x= 1 or 2) in which the phospholes are co-ordinated as tertiary phosphines through the phosphorus atoms. Thermolysis of these compounds gives decarbonylation compounds containing modified phosphole ligands. Phosphorus–carbon bonds either to the phenyl group or within the five-membered ring have been cleaved. The X-ray structure of the main product [Os3(CO)9(µ3-PhPCHCMeCMeCH)]1 shows that the organic µ3 ligand is a six-electron donor which is co-ordinated differently from the corresponding eight-electron donating ligand derived from 1-phenylphosphole in the cluster [Os3(CO)9(µ3-PhPCHCHCHCH)]. There is evidence for the reversible generation of this alternative from, 3, of the methylated compound 1 by photolysis. A minor product of the thermolysis is the hydrido cluster [Os3(µ-H)(µ-[graphic omitted]H)(µ3-C6H4)(CO)9]2 which contains a five-membered phospholyl ring and an o-phenylene (benzyne) ligand which originated from the phenyl group. The X-ray structure shows that the phospholyl ligand bridges two osmium atoms as a phosphido ligand through the phosphorus atom. The major and minor products, 1 and 2, are both derived by C–P bond cleavage, either in the phosphole ring or to the phenyl substituent respectively.

Electrochemical behavior of copper complexes with substituted polypyridinic ligands: An experimental and theoretical study

Experimental redox potentials of the couples [Cu(R-L ( n ))(CH 3CN)] (2+,+), where L (1) is bis-(pyridine-2-ylmethyl)-benzylamine, L (2) is (pyridine-2-ylethyl)(pyridine-2-ylmethyl)-benzylamine, and R is H, Me, or CF 3, were determined in dichloromethane solution. The compounds exhibited one simple quasi-reversible wave over the measured potential range of -500 to +1200 mV, and the E 1/2 values varied from +200 to +850 mV versus SCE. These experimental values were correlated with redox potentials calculated using density functional theory. The optimized geometries and the predicted redox potentials were obtained using the BP86 functional and a combination of the basis sets LACV3P** (for Cu) and cc-pVTZ(-f) (for light atoms). A distortion analysis of all of the optimized geometries for both oxidation states was performed using the generalized interconversion coordinate phi. A linear relation was obtained between this parameter and the redox potentials. However, the [Cu(CF 3-L (1))(CH 3CN)] (+) complex showed the largest deviation, which was explained by the more-rigid structure of the ligand.

Synthesis, structure and oxidation studies of a dinuclear copper(I)–copper(II) complex: [Cu2(bdpdz)2](ClO4)3

Abstract A dinuclear copper complex containing the ligand 3,6-bis(di-2-pyridylmethyl) pyridazine, bdpdz, [Cu2(bdpdz)2](ClO4)3, was prepared and its structure determined by X-ray analysis. The compound consists of a dinuclear mixed valence copper(I)–copper(II) entity with localised valences, co-ordinated to two bridging ligand molecules. The geometry around the copper(I) centre is distorted tetrahedral, while that of the copper(II) centre is tetragonally distorted octahedral. Oxidation studies reveal that the compound does not exhibit phenolase activity.

DICOPPER(II) COMPLEXES WITH HEXAAZA BINUCLEATING LIGANDS DERIVED FROM ISOPHTHALDEHYDE AND DI(2-PYRIDYL)METHYLAMINE

Abstract New N6 ligands derived from isophthaldehyde and di(2-pyridyl) methylamine were synthesized, in order to probe the corresponding copper complexes as model systems of tyrosinase. Copper(II) complexes of the N6 ligands: α,α′-bis(di (2-pyridyl)methylimino)-m-xylene (m-xylN(DPM)2) and α,α′-bis(di (2-pyridyl) methylamino)-m-xylene (m-xylNH(DPM)2) were obtained. [Cu2(m-xylN-(DPM)2(OCH3)2ClO4]ClO4 (1) and [Cu2(m-xylN(DPM)2) (OH)2ClO4]ClO4 (2) were isolated by the oxidation reaction of the cuprous species with molecular oxygen in methanol and dichloromethane solutions, respectively. Neither of the two dicopper(II) complexes showed insertion of oxygen at the arene ring under the used experimental conditions. [Cu2(m-xylNH(DPM)2Cl4]·2H2O (3) was synthesized by the direct reaction of the reduced organic ligand with cupric chloride. X-ray structures are reported: [Cu2(m-xylN-(DPM2(OCH3)2ClO4]ClO4 (4), monoclinic P2 1 n , a=15.099(4), b=11.974(4), c=19.928(5) A , β=93.95(1)°, Z=4, R=0.049 ; [Cu2(m-xylN(DPM)2) (OH)2ClO4]ClO4 (2), orthorbic P212121, a=14.188(4), b=14.275(3) c=16.763(4) A , Z=4, R=0.062 ; [Cu2(m-xylNH(DPM)2Cl4]·2H2O (3), monoclinic P2 1 c , a=13.353, b=17.030(2) , c=15.547(2) A , β=112.38(1)°, Z=4, R=0.043 . The coordination geometries of the Cu(II) ion in 1 and 2 are best described as tetragonally distorted octahedral, while in 3 it is trigonal bipyramidal. Compounds 1 and 2 are doubly bridged by methoxo and hydroxo groups; the bridging angles for 1 are Cu(1)O(1)Cu(2) = 100.0(2)° and Cu(1)O(2)Cu(2) = 99.0(1)°, and for 2 Cu(2)O(1)Cu(1) = 98.2(4) and Cu(2)O(1)Cu(1) = 96.4(4)°. The methoxo complex 1 is antiferromagnetic (TM = 338 K) while the hydroxo complex 2 and the dicopper (II) complex 3 are paramagnetic.