Stoichiometry and products of transmetalation of dimeric copper(I) complexes L2Cu2X2 (L is an N,N,N′,N′-tetraalkylethylenediamine; X = Cl or Br) by M(NS)2 reagents in aprotic solvents

Dimeric copper(I) complexes L₂Cu₂X₂ react with 1 and 2 mol of M(NS)₂ reagents in aprotic solvents to give quantitative yields of products LMX₂ and (NS)M(X,X)M(NS), respectively. Here, L = N,N,N′N′-tetraethylethylenediamine, X = Cl or Br, M = Co, Ni, Cu and Ns = S-methylisopropylidenehydrazinecarbodithioate. Dimers (NS)Cu(X,X)Cu(NS) are oxidatively unstable. LCoCl₂ crystallizes in the monoclinic space group P2₁/c (C_2h⁵): a = 7.345(1), b = 11.801(1), c = 17.478(2) Å, β = 104.98(1)°, Z = 4. The electronic spectra of LMX₂ and (NS)M(X,X)M(NS) complexes are discussed.     

The reaction of amines with N,N′-ethylenebis(salicylideneiminato)(nitrato)-iron(III) and related complexes

The title compound, Fe(salen)NO₃, was reacted with imidazole, 1-methylimidazole, piperidine, and morpholine in either chloroform or dichloromethane solution. The reactions were monitored with proton NMR and electronic spectra and conductance measurements. The imidazole bases appeared to react with the complex in a 2:1 fashion with displacement of the nitrate, producing a high-spin iron(III) complex. The secondary amines promoted hydrolysis with any trace water present to form [Fe(salen)]₂O. The chloro complex, Fe(salen)Cl, did not react with the imidazole bases, but did form the μ-oxo complex when a large excess of piperidine was present. The N,N′-phenylenebis-(salicylideneimine) complex, Fe-(salphen)NO₃, was found to precipitate from an imidazole (im) chloroform solution as the high-spin complex, Fe(salphen)NO₃·2im.     

Formation of the Si-B bond: insertion reactions of silylenes into B-X(X = F,Cl, Br,O, and N) bonds

The insertion reactions of the silylene H₂Si with H₂BXH_n-1 (X?=?F, Cl, Br, O, N; n?=?1, 1, 1, 2, 3) have been studied by DFT and MP2 methods. The calculations show that the insertions occur in a concerted manner, forming H₂Si(BH₂)(XH_n-1). The essences of H₂Si insertions with H₂BXH_n-1 are the transfers of the σ electrons on the Si atom to the positive BH₂ group and the electrons of X into the empty p orbital on the Si atom in H₂Si. The order of reactivity in vacuum shows the barrier heights increase for the same-family element X from up to down and the same-row element X from right to left in the periodic table. The energies relating to the B-X bond in H₂BXH_n-1, and the bond energies of Si-X and Si-B in H₂Si(BH₂)(XH_n-1) may determine the preference of insertions of H₂Si into B-X bonds for the same-column element X or for the same-row element X. The insertion reactions in vacuum are similar to those in solvents, acetone, ether, and THF. The barriers in vacuum are lower than those in solvents and the larger polarities of solvents make the insertions more difficult to take place. Both in vacuum and in solvents, the silylene insertions are thermodynamically exothermic.

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Graphical Abstract The insertion process of H₂Si and H₂BXH_n-1(X?=?F, Cl, Br, O, and N; n?=?1, 1 , 1, 2, 3).

     

A new reaction mode of germanium-silicon bond formation: insertion reactions of H2GeLiF with SiH3X (X = F, Cl, Br)

A combined density functional and ab initio quantum chemical study of the insertion reactions of the germylenoid H₂GeLiF with SiH₃X (X?=?F, Cl, Br) was carried out. The geometries of all the stationary points of the reactions were optimized using the DFT B3LYP method and then the QCISD method was used to calculate the single-point energies. The theoretical calculations indicated that along the potential energy surface, there were one precursor complex (Q), one transition state (TS), and one intermediate (IM) which connected the reactants and the products. The calculated barrier heights relative to the respective precursors are 102.26 (X?=?F), 95.28 (X?=?Cl), and 84.42 (X?=?Br) kJ mol^-1 for the three different insertion reactions, respectively, indicating the insertion reactions should occur easily according to the following order: SiH₃-Br?>?SiH₃-Cl?>?SiH₃-F under the same situation. The solvent effects on the insertion reactions were also calculated and it was found that the larger the dielectric constant, the easier the insertion reactions. The elucidations of the mechanism of these insertion reactions provided a new reaction model of germanium-silicon bond formation.     

Dioxo-, oxothio- and dithio-tungsten(VI) and tungsten(V) complexes of the ligand N,N′-Dimethyl-N,N′-bis(2-mercaptophenyl)ethylenediamine

Synthesis of complexes cis,cis-W^VOXL (X=Cl, NCS), cis,trans-W^VOXL (X=Cl, OPh, SPh) and cis,trans-W^VIE₂L (E₂=O₂, OS, S₂) of the title ligand LH₂ are reported. cis,cis-W^VOCIL crystallises in space group P2₁/c with a=13.6541(9) Å, b=7.1555(11) Å, c=18.198(2) Å, β=95.294(6)°, V=1770.4(3) ų and Z=4 while the cis,trans isomer crystallises in space group P2₁/n with a=10.361(3) Å, b=14.141(4) Å, c=12.213(5) Å, β=102.56(3)°, V=1747(2) ų and Z=4. cis,trans-W^VIS₂L crystallises in space group P2₁/n with a=10.645(2) Å, b=13.929(2) Å, c=12.189(2) Å, β=103.14(2)°, V=1760(1) ų and Z=4. A short CH₃···Cl distance of 3.067(7) Å and an acute OWCl angle of 94.1(2)° are seen in cis,cis-W^VOClL, which converts to the cis,trans form on heating in MeCN. The latter isomer features a CH₃···Cl distance of 3.38(2) Å and an OWCl angle of 105.1(8)°. Electrochemical and EPR data are reported. In particular, cis,trans-W^VIE₂L may be reduced to [W^VE₂L]^–. EPR properties of these anions and those of complexes W^VOXL are discussed in the context of W^V centres in tungsten enzymes.     

Synthesis and spectroscopic studies of platinum(II) complexes of N,N′-dicyclohexylethylenediamine

The platinum(II) complexes of the formula [Pt(DCHEDA)X₂], where DCHEDA is N,N′-dicyclohexylethylenediamine and X⁻ is CL⁻, Br⁻, I⁻, 0.5C₂O₄²⁻ (oxalate), 0.5C₃H₂O₄²⁻ (malonate), 0.5C₉H₄O₆²⁻ (4-carboxyphthalate), 0.5S₂O₃²⁻ or 0.5SO₄²⁻, have been synthesized and characterized by UVVis, IR, and ¹H NMR spectral techniques. All the above complexes are non-electrolytes in DMF/H₂O, except the sulphate complex which becomes a 1:1 electrolyte after incubation for 24 h at 28 °C. The halide complexes were also studied by X-ray photoelectron spectroscopy and these data suggest that there is π-bonding from platinum to halide in these complexes. The oxalate, malonate and sulphate bind in their complexes as bidentate ligands to platinum through two oxygen atoms whereas the thiosulphate in its complex binds as a bidentate ligand to platinum through one oxygen atom and one sulphur atom.     

Copper(II) complexes with 2,2′-biimidazole. Preparation and crystal structure determination of a complex of stoichiometry Cu1.5Cl3(H2bim)2 (H2bim=2,2′-biimidazole)

By reacting 2,2′-biimidazole and copper(II) chloride in aqueous HCl we obtained the complex CuCl₂(H₂bim) as the main product and a compound with stoichiometry Cu_1.5Cl₃(H₂bim)₂ as a byproduct. The structure of the latter compound has been determined by X-ray analysis: monoclinic, a= 794.0(3), b=3146.8(6), c=722.9(4) pm, β= 114.2(1)°, space group P21/c. The compound actually contains two species, namely [Cu(H₂bim)₂]Cl₂ and [CuCl₂(H₂bim)] in a 1:2 molar ratio.     

The oxidation of N,N′-bis(4-aminophenyl)-N,N′-dimethylethylenediamine (BED) by rat liver

We have examined the oxidation of N,N′-bis(4-aminophenyl)-N,N′-dimethylethylenediamine (BED) by tissue homogenates and fractions of liver homogenates. We find that this agent both gives osmiophilic deposits in tissue blocks and readily increases the uptake of oxygen by hepatic homogenates. The highest activity was in the mitochondrial and, next, in the microsomal fractions. Kinetic evidence indicates that the former represents two enzymatic activities while the latter is only a single site. The activity was greatest in the outer membrane of the mitochondria, in agreement with electron micrographic studies and in the rough microsomal fraction. Further, it was very sensitive to both formaldehyde and detergents. The activity was not well associated with either monamine oxidase (benzylamine substrate) or xanthine oxidase activities. Activity was observed in a large number of tissues.     

The reactions of organosulfur transfer reagents with Fe2(CO)9 and the synthesis of the Fe2(CO)6 derivative of α-lipoic acid

Treatment of Fe₂(CO)₉ with sulfur-transfer reagents of the types ImideSSImide and RSSImide where H-imide = phthalimide, succinimide, benzimidazole, morpholine and piperazine, and R  CH₂Ph and CMe₃ leads to cleavage of both the sulfursulfur bond and the sulfurnitrogen bond to give Fe₃(CO)₉S₂ in varying yields, some Fe₂(CO)₆S₂ plus low yields of the appropriate dimers of the type Fe₂(CO)₆(SR)(SR′), where R = R′ = phthal imido, CH₂Ph, CMe₃ and R = CH₂Ph, CMe₃, R′ = phthalimido. The naturally occurring cyclic disulfide D,L-α-lipoic acid, its methyl ester and amide react with Fe₂(CO)₉ to give Fe₂(CO)₆ derivatives wherein the sulfursufur bond has been broken.     

Theoretical potential scans and vibrational spectra of vinyl selenonyl halides CH2=CH–SeO2X (X is F, Cl and Br)

The structure and conformational stability of vinyl selenonyl fluoride, chloride and bromide CH₂=CH–SeO₂X (X is F, Cl and Br) were investigated using density functional B3LYP/6-311+G** and ab initio MP2/6-311+G** calculations. From the calculations the molecules were predicted to exist only in the non-planar gauche conformation with the vinyl C=C group almost eclipsing one of the selenonyl Se=O bonds as a result of conjugation between the two moieties. Single-minimum potential scans were calculated at the DFT level for the molecules. The vibrational frequencies were computed using B3LYP/6-311+G**. Normal coordinate calculations were then carried out and potential energy distributions were calculated for the three molecules in the gauche conformation.Figure Potential function for the asymmetric torsion in vinyl selenonyl fluoride (dotted line), chloride (dashed line) and bromide (solid line) as determined at the DFT-B3LYP/6-311+G** level     

Theoretical study of the hydroxylation of phenolates by the Cu2O2(N,N′-dimethylethylenediamine)2 2+ complex

Tyrosinase catalyzes the ortho hydroxylation of monophenols and the subsequent oxidation of the diphenolic products to the resulting quinones. In efforts to create biomimetic copper complexes that can oxidize C–H bonds, Stack and coworkers recently reported a synthetic μ-η²:η²-peroxodicopper(II)(DBED)₂ complex (DBED is N,N′-di-tert-butylethylenediamine), which rapidly hydroxylates phenolates. A reactive intermediate consistent with a bis-μ-oxo-dicopper(III)-phenolate complex, with the O–O bond fully cleaved, is observed experimentally. Overall, the evidence for sequential O–O bond cleavage and C–O bond formation in this synthetic complex suggests an alternative mechanism to the concerted or late-stage O–O bond scission generally accepted for the phenol hydroxylation reaction performed by tyrosinase. In this work, the reaction mechanism of this peroxodicopper(II) complex was studied with hybrid density functional methods by replacing DBED in the μ-η²:η²-peroxodicopper(II)(DBED)₂ complex by N,N′-dimethylethylenediamine ligands to reduce the computational costs. The reaction mechanism obtained is compared with the existing proposals for the catalytic ortho hydroxylation of monophenol and the subsequent oxidation of the diphenolic product to the resulting quinone with the aim of gaining some understanding about the copper-promoted oxidation processes mediated by 2:1 Cu(I)O₂-derived species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis and characterization of triaminecobalt(III) complexes and acid hydrolysis kinetics of fac-[Codpt(H2O)nX3−n]n+ (X = Cl,Br; n = 0,1,2)

The complexes CodptX₃ and [Codpt(H₂O)X₂]ClO₄ (X = Cl, Br; dpt = dipropylenetriamine = NH(CH₂CH₂CH₂NH₂)₂) have been prepared and characterized. Rate constants (s⁻¹) for aqueous solution at 25 °C and μ = 0.5 M (NaClO₄), for the acid-independent sequential ractions.

have been measured spectrophotometrically. For X = Cl: k₁ ⋍ 2 × 10⁻², k₂ = 1.7 × 10⁻⁴ and k₃ = 4.8 × 10⁻⁶, and for X = Br: k₁ ⋍ 2 × 10⁻², k₂ = 5.25 × 10⁻⁴ and k₃ = 2.5 × 10⁻⁵ The primary equation was found to be acid independent, while the secondary and tertiary aquations were acid-inhibited reactions. For the second step, the rate of the reaction was given by the rate equation

where C_t is the complex concentration in the aqua-and hydroxodihalo species, k′₂ is the rate constant for the acid-dependent pathway and K_a is the equilibrium constant between the hydroxo and aqua complex ions. The activation parameters were evaluated, for X = Cl: ΔH^≠₂ = 106.3 ± 0.4 kJ mol⁻¹ and ΔS^≠₂ = 40.2 ± 1.7 J K⁻¹ mol⁻, and for X = Br: ΔH^≠₂ = 91.6 ± 0.4 kJ mol⁻¹ and ΔS^≠₂ = 0.4 ± 1.7 J K⁻¹ mol⁻¹. The results are discussed and detailed comparisons of the reactivities of these complexes with other haloaminecobalt(III) species are presented.     

Binuclear metal complexes. 59. Synthesis and magnetism of dicopper(II) and copper(II)-nickel(II) complexes with N,N′-ethylenedisalicylamidatocuprate(II)

The complexes [Cu(samen)Cu(L)] and [Cu(samen)Ni(L)₂] (Lbpy, phen) have been synthesized by the reaction of sodium N,N′-ethylenedisalicylamidatocuprate(II) pentahydrate (Na₂- [Cu(samen)]·5H₂O), a divalent metal ion, and 2,2′- dipyridyl or 1,10-phenanthroline. Cryomagnetic data for the CuCu complexes did not fit the Bleaney- Bowers equation; but the data did fit a modified Bleaney-Bowers equation

with a large negative J and a significant negative θ, suggesting that a considerable magnetic interaction operates between essentially planar [Cu(samen)Cu(L)] molecules. The magnetisms of the CuNi complexes were well interpreted in terms of the susceptibility equation based on the Heisenberg model. An antiferromagnetic spin-exchange interaction (J= −13∼−14 cm⁻¹) was suggested between the metal ions.     

The reactivity of bromoform with [Au(CH2)2PPh2]2. The completion of the halomethane series CHyX4−y (y=3,2,1,0; X=Cl,Br, I) and reactivity with [Au(CH2)2PPh2]2

The reaction of [Au(CH₂)₂PPh₂]₂ with excess CHBr₃ in benzene initially gives [Au(CH₂)₂PPh₂]₂₋ (CHBr₂)Br. This observation establishes that halomethanes, CH_yX_4−y (y=3,2,1,0; X=Cl, Br, I), react with [Au(CH₂)₂PPh₂]₂ to initially give Au(II) adducts of the general form [Au(CH₂)₂PPh₂]₂₋(CH_yX_3−y)X (y=3,2,1,0) via oxidative addition across the carbon-halogen bond. The order of reactivity inversely follows the order of carbon-halogen bond dissociation energies of haloalkanes. Methyl chloride is the only halomethane of the series that does not give a Au(II) adduct under similar reaction conditions.     

The thermal decomposition of group IIB metal(II) halide complexes. Part III. Low frequency infrared spectra and thermal behaviour of N,N,N′-trimethylethylenediamine complexes

The group IIb metal dihalide-N,N,N′-trimethylethylenediamine complexes are described. Low frequency infrared spectroscopic studies and conductance data have provided evidence for the formulation and structure of the complexes. The thermal behaviour of these complexes has been examined by thermogravimetry and differential scanning calorimetry. For cadmium and mercury complexes complete loss of ligand occurred followed eventually by sublimation of the metal halide, whereas the zinc complexes sublimed unchanged.