Binuclear platinum(II) complexes of the type [Pt2Cl2(μ-L)(μ-pz) (PR3)2] [L=SC5H4N or S2P(OR′)2]

Binuclear platinum complexes of general formula [Pt₂Cl₂(-L)(-pz)(PR₃)₂] [L = 2-Spy, py = pyridyl, S₂P(OR)₂ (R = Et or i-Pr); pz = pyrazolate; PR₃ = PEt₃, PMe₂Ph or PMePh₂] have been synthesized. They adopt a cis configuration in which the phosphine ligands are trans to the single atom bridging ligand, L.     

NMR study of ligand exchange and electron self-exchange between oxo-centered trinuclear clusters [Fe3(μ3-O)(μ-O2CR)6(4-R'py)3](+/0)

The syntheses, single crystal X-ray structures, and magnetic properties of the homometallic μ?-oxo trinuclear clusters [Fe?(μ?-O)(μ-O?CCH?)?(4-Phpy)?](ClO?) (1) and [Fe?(μ?-O)(μ-O?CAd)?(4-Mepy)?](NO?) (2) are reported (Ad = adamantane). The persistence of the trinuclear structure within 1 and 2 in CD?Cl? and C?D?Cl? solutions in the temperature range 190-390 K is demonstrated by 1H NMR. An equilibrium between the mixed pyridine clusters [Fe?(μ?-O)(μ-O?CAd)?(4-Mepy)(3-x)(4-Phpy)(x)](NO?) (x = 0, 1, 2, 3) with a close to statistical distribution of these species is observed in CD?Cl? solutions. Variable-temperature NMR line-broadening made it possible to quantify the coordinated/free 4-Rpy exchanges at the iron centers of 1 and 2: k(ex)2?? = 6.5 ± 1.3 × 10?1 s?1, ΔH(?) = 89.47 ± 2 kJ mol?1, and ΔS(?) = +51.8 ± 6 J K?1 mol?1 for 1 and k(ex)2?? = 3.4 ± 0.5 × 10?1 s?1, ΔH(?) = 91.13 ± 2 kJ mol?1, and ΔS(?) = +51.9 ± 5 J K?1 mol?1 for 2. A limiting D mechanism is assigned for these ligand exchange reactions on the basis of first-order rate laws and positive and large entropies of activation. The exchange rates are 4 orders of magnitude slower than those observed for the ligand exchange on the reduced heterovalent cluster [Fe(III)?Fe(II)(μ?-O)(μ-O?CCH?)?(4-Phpy)?] (3). In 3, the intramolecular Fe(III)/Fe(II) electron exchange is too fast to be observed. At low temperatures, the 1/3 intermolecular second-order electron self-exchange reaction is faster than the 4-Phpy ligand exchange reactions on these two clusters, suggesting an outer-sphere mechanism: k?2?? = 72.4 ± 1.0 × 103 M?1 s?1, ΔH(?) = 18.18 ± 0.3 kJ mol?1, and ΔS(?) = -90.88 ± 1.0 J K?1 mol?1. The [Fe?(μ?-O)(μ-O?CCH?)?(4-Phpy)?](+/0) electron self-exchange reaction is compared with the more than 3 orders of magnitude faster [Ru?(μ?-O)(μ-O?CCH?)?(py)?](+/0) self-exchange reaction (ΔΔG(exptl)(?298) = 18.2 kJ mol?1). The theoretical estimated self-exchange rate constants for both processes compare reasonably well with the experimental values. The equilibrium constant for the formation of the precursor to the electron-transfer and the free energy of activation contribution for the solvent reorganization to reach the electron transfer step are taken to be the same for both redox couples. The larger ΔG(exptl)(?298) for the 1/3 iron self-exchange is attributed to the larger (11.1 kJ mol?1) inner-sphere reorganization energy of the 1 and 3 iron clusters in addition to a supplementary energy (6.1 kJ mol?1) which arises as a result of the fact that each encounter is not electron-transfer spin-allowed for the iron redox couple.     

Synthesis and magnetic properties of copper(II)-MII-copper(II) trinuclear complexes with N,N′-bis(2-aminoethyl)oxamidocopper(II) [M = Co and Ni]

Summary Two novel trinuclear complexes were prepared, namely [Cu₂(oxae)₂(H₂O)₂M] (ClO₄)₂, [oxae = N,N-bis(2-aminoethyl) oxamido dianion; M = Co and Ni]. Based on elemental analyses, conductivity measurements and i.r. spectra, the complexes are proposed to have extended oxamidobridged structures. The magnetic susceptibility of [Cu₂-(oxae) ₂(H₂O)₂Co](ClO₄)₂ were measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian, =–2J(₁·₂·₂·₃). The exchange integral, J, was found to be equal to –29.2 cm^–1, indicating an antiferromagnetic spin-exchange interaction between the adjacent metal ions.     

Copper(II), nickel(II) and palladium(II) complexes of the diamide ligand N,N′-bis(2-carbamoylethyl)ethylenediamine (H2L) and the crystal structure of the carbonyl-oxygen-bonded copper(II) complex [Cu(H2L)](ClO4)2

The preparation of the diamide ligand N,N-bis(2-carbamoylethyl)ethylenediamine (H2L) by Michael addition of ethylenediamine to acrylamide is described. The copper(II) complex [Cu(H2L)](ClO4)2 and the deprotonated complex [CuL]·H2O have been prepared and characterized as has the blue octahedral nickel(II) complex [Ni(H2L)](ClO4)2. The crystal structure of the carbonyl-oxygen-bonded copper(II) complex [Cu(H2L)] (ClO4)2 has been determined (R=5.5%). The stepwise protonation equilibria of the ligand have been studied by potentiometric titration, giving values of logK1= 8.71 and logK2=5.74 at 25°C and I=0.1moldm–3 (NaClO4). The interaction of copper(II) with the ligand (H2L/Cu(II)=1:1) can be fitted to the set of equilibria:With nickel(II), only two complexes, [Ni(H2L)]2+ and [NiL], occur and they have formation constants of log110=7.39 and log 11–2=–11.49. With palladium- (II) the system is similar to that with copper(II) with three complex species, 110, 11–1 and 11–2, with log 110=15.48, log 11–1=11.88 and log 11–2=7.32.     

A study of zinc complexes of the metalloligand [Pt2(μ-S)2(PPh3)4] of the type [Pt2(μ-S)2(PPh3)4ZnL]+ (L = bidentate chelating ligand)

Reactions of [Pt₂(μ-S)₂(PPh₃)₄] with zinc acetate and an ancillary chelating ligand L (HL = 8-hydroxyquinoline, 8-tosylaminoquinoline or maltol) with added trimethylamine in methanol give new cationic platinum–zinc sulfide aggregates [Pt₂(μ-S)₂(PPh₃)₄ZnL]⁺, isolated as their BF₄^? salts. The complexes were characterized by NMR spectroscopy, ESI mass spectrometry, microelemental analysis, and an X-ray structure determination of the tosylamidoquinoline derivative [Pt₂(μ-S)₂(PPh₃)₄Zn(TAQ)]BF₄, which showed a distorted tetrahedral coordination geometry at zinc. Additional examples, containing picolinate, dithiocarbamate, or dithiophosphinate ligands were also synthesized and partly characterized in order to demonstrate a wider range of available derivatives.     

Synthesis and Characterisation of Luminescent [CrIII2L(μ-carboxylato)]3+ Complexes with High-Spin S=3 Ground States (L=N6S2 donor ligand)

The synthesis, structure, magnetic, and photophysical properties of two dinuclear, luminescent, mixed-ligand [Cr^III₂L(O₂CR)]³⁺ complexes (R=CH₃ ( 1 ), Ph ( 2 )) of a 24-membered binucleating hexa-aza-dithiophenolate macrocycle (L)²⁻ are presented. X-ray crystallographic analysis reveals an edge-sharing bioctahedral N₃Cr(μ-SR)₂(μ_1,3-O₂CR)CrN₃ core structure with μ_1,3-bridging carboxylate groups. A ferromagnetic superexchange interaction between the electron spins of the Cr³⁺ ions leads to a high-spin (S=3) ground state. The coupling constants (J=+24.2(1) cm⁻¹ ( 1 ), +34.8(4) cm⁻¹ ( 2 ), H=−2JS₁S₂) are significantly larger than in related bis-μ-alkoxido-μ-carboxylato structures. DFT calculations performed on both complexes reproduce both the sign and strength of the exchange interactions found experimentally. Frozen methanol-dichloromethane 1 : 1 solutions of 1 and 2 luminesce at 750 nm when excited into the ⁴LMCT state on the ⁴A₂ → ²T₁ (ν₂) bands (λ_exc=405 nm). The absolute quantum yields (Φ_L) for 1 and 2 were found to be strongly temperature dependent. At 77 K in frozen MeOH/CH₂Cl₂ glasses, Φ_L=0.44±0.02 (for 1 ), Φ_L=0.45±0.02 (for 2 ).     

Tunability of the M(II)M(III)/M(II)(2) and M(III)(2)/M(II)M(III) (M=Mn, Co) couples in bis-μ-O,O'-carboxylato-μ-OR bridged complexes

A comparison of the electrochemical properties of a series of dinuclear complexes [M(2)(L)(RCO(2))(2)](+) with M = Mn or Co, L = 2,6-bis(N,N-bis-(2-pyridylmethyl)-sulfonamido)-4-methylphenolato (bpsmp(-)) or 2,6-bis(N,N-bis(2-pyridylmethyl)aminomethyl)-4-tert-butylphenolato (bpbp(-)) and R = H, CH(3), CF(3) or 3,4-dimethoxybenzoate demonstrates: (i) The electron-withdrawing sulfonyl groups in the backbone of bpsmp(-) stabilize the [M(2)(bpsmp)(RCO(2))(2)](+) complexes in their M(II)(2) oxidation state compared to their [M(2)(bpbp)(RCO(2))(2)](+) analogues. Manganese complexes are stabilised by approximately 550 mV and cobalt complexes by 650 mV. (ii) The auxiliary bridging carboxylato ligands further attenuate the metal-based redox chemistry. Substitution of two acetato for two trifluoroacetato ligands shifts redox couples by 300-400 mV. Within the working potential window, reversible or quasi-reversible M(II)M(III)? M(II)(2) processes range from 0.31 to 1.41 V for the [Co(2)(L)(RCO(2))(2)](+/2+) complexes and from 0.54 to 1.41 V for the [Mn(2)(L)(RCO(2))(2)](+/2+) complexes versus Ag/AgCl for E(M(II)M(III)/M(II)(2)). The extreme limits are defined by the complexes [M(2)(bpbp)(CH(3)CO(2))(2)](+) and [M(2)(bpsmp)(CF(3)CO(2))(2)](+) for both metal ions. Thus, tuning the ligand field in these dinuclear complexes makes possible a range of around 0.9 V and 1.49 V for the one-electron E(M(II)M(III)/M(II)(2)) couple of the Mn and Co complexes, respectively. The second one-electron process, M(II)M(III)? M(III)(2) was also observed in some cases. The lowest potential recorded for the E°(M(III)(2)/M(II)M(III)) couple was 0.63 V for [Co(2)(bpbp)(CH(3)CO(2))(2)](2+) and the highest measurable potential was 2.23 V versus Ag/AgCl for [Co(2)(bpsmp)(CF(3)CO(2))(2)](2+).     

Binuclear Osmium μ-Oxocarboxylate Complexes [Os2(μ-O)(μ-O2CR)2Cl4L2] (R = CH3, CCl3; L = PPh3, AsPh3) and Their Electrochemical Behavior in Dichloromethane

Cyclic voltammetry and galvanostatic coulometry techniques were used to determine how the redox properties of osmium binuclear -oxocarboxylates [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PPh₃ and R = CH₃; L = AsPh₃) are influenced by the nature of the bridging carboxylate ligand RCOO^– and ligand L. It was shown that all compounds in solution of dichloromethane undergo two single-electron reduction processes. The data obtained were compared with the DFT calculations of the electronic structure of the model complexes [Os₂ ^IV(-O)(-O₂CR)₂Cl₄L₂] (R = CH₃, CCl₃; L = PH₃ and R = CH₃; L = AsH₃).     

Synthesis and magnetic properties of copper(II)-lanthanoid(III)-copper(II) trinuclear complexes with N,N′-bis(2-aminoethyl)-oxamido ligand

Summary Ten novel -oxamido trinuclear complexes, namely Cu₂–(oxae)₂Ln(ClO₄)₃ (Ln = Y, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb), where oxae donotes the N,N-bis(2-aminoethyl)-oxamido dianion, were prepared and characterized. The magnetic susceptibility of Cu₂(oxae)₂Gd(ClO₄)₃ was measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator . The exchange integrals J _(Gd-Cu) and J _Gd-Cu were found to be 2.37 and –0.71cm^-1, respectively, indicating that very weakly ferromagnetic spin-exchange interaction operates between copper(II) and gadolinium(III) ions.Visiting scholar: Qufu Normal University.     

Two heptacopper(II) disk complexes with a [Cu(7)(μ(3)-OH)(4)(μ-OR)(2)](8+) core

The reaction of CuX(2) (X(-) ≠ F(-)) salts with 1 equiv of 3-pyridyl-5-tert-butylpyrazole (HL) in basic methanol yields blue solids, from which disk complexes of the type [Cu(7)(μ(3)-OH)(4)(μ-OR)(2)(μ-L)(6)](2+) and/or the cubane [Cu(4)(μ(3)-OH)(4)(HL)(4)](4+) can be isolated by recrystallization under the appropriate conditions. Two of the disk complexes have been prepared in crystalline form: [Cu(7)(μ(3)-OH)(4)(μ-OCH(2)CF(3))(2)(μ-L)(6)][BF(4)](2) (2) and [Cu(7)(μ(3)-OH)(4)(μ-OCH(3))(2)(μ-L)(6)]Cl(2)·xCH(2)Cl(2) (3·xCH(2)Cl(2)). The molecular structures of both compounds as solvated crystals can be described as [Cu?Cu(6)(μ-OH)(4)(μ-OR)(2)(μ-L)(6)](2+) (R = CH(2)CF(3) or CH(3)) adducts. The [Cu(6)(μ-OH)(4)(μ-OR)(2)(μ-L)(6)] ring is constructed of six square-pyramidal Cu ions, linked by 1,2-pyrazolido bridges from the L(-) ligands and by basal, apical-bridging hydroxy or alkoxy groups, while the central Cu ion is bound to the four metallamacrocyclic hydroxy donors in a near-regular square-planar geometry. The L(-) ligands project above and below the metal ion core, forming two bowl-shaped cavities that are fully (R = CH(2)CF(3)) or partially (R = CH(3)) occupied by the alkoxy R substituents. Variable-temperature magnetic susceptibility measurements on 2 demonstrated antiferromagnetic interactions between the Cu ions, yielding a spin-frustrated S = (1)/(2) magnetic ground state that is fully populated below around 15 K. Electrospray ionization mass spectrometry, UV/vis/near-IR, and electron paramagnetic resonance measurements imply that the heptacopper(II) disk motif is robust in organic solvents.     

Synthesis,structures and magnetic properties of tetranuclear heterometallic complexes [Cu3M] (M = Mn(II) Co(II) and Ni(II)) based on an oxamido-bridged ligand

Transition Metal Chemistry - Three tetranuclear heterometallic coordination compounds of the general formula [(CuL)2M(CuL·CH3OH)](ClO4)2 [(M?=?Mn(for 2), Co(for 3) and Ni(for 4)]...     

Solution and solid state characterization of oxo-centered trinuclear iron(III) acetate complexes [Fe3(μ3-O)(μ-OAc)6(L)3]+

[Fe(3)(μ(3)-O)(μ-OAc)(6)(py)(3)][FeBr(4)](2)[py·H], complex (1), (OAc is acetate) was prepared from the reaction of FeBr(3) with pyridine in 1.2 molar aqueous HBr and 2.4 molar aqueous CH(3)COOH. Recrystallization of 1 in acetonitrile produced the [Fe(3)(μ(3)-O)(μ-OAc)(6)(py)(3)][FeBr(4)] complex (2). Both complexes were characterized by IR and (1)H NMR spectroscopies and their structures were studied using the single-crystal diffraction method. There is a lack of thorough characterization of the titled compounds in solution. Paramagnetic (1)H NMR is introduced as a good probe for the characterization of a family of titled compounds in solution when the L ligand coordinated to iron varies as: CH(3)OH, CH(3)CN, DMSO, H(2)O, py and acetone.     

Bonding properties of copper(II)—N chromophores: Preparation,structure, and spectroscopic properties of ethylenediaminecopper(II) complexes. Molecular structure of [Cu(ethylenediamine)(pyridine)2(ClO4)2]

Summary Ethylenediaminecopper(II) perchlorate complexes of the [Cu(ethylenediamine)L₂(ClO₄)₂] type, where L = imidazole, N-methylimidazole, 2-methylimidazole, 4-methylimidazole, and pyridine, have been prepared and characterized by elemental analyses, and electronic, vibrational, and e.p.r. spectroscopic measurements. The molecular structure of [Cu(ethylenediamine)(pyridine)₂(ClO₄)₂] has been determined by three-dimensional X-ray diffraction data. The Cu^II ion is coordinated by one ethylenediamine and two pyridine ligands forming an equatorial plane, and by two perchlorate anions located on the z axis. The pyridine ligands incline at 54.9 ° to the CuN₄ plane suggesting virtually no -interaction in the complex. Similar structures with a CuN₄ coordination plane are proposed for other complexes based on the spectroscopic data. The bonding properties of these complexes are elucidated and discussed with reference to the electronic structures deduced from Gaussian analyses of their LF spectra.     

Quantum chemical study of pyridine addition to Ni(II) β-diketonate complexes

The addition reaction of two pyridine molecules to Ni(II) β-diketonate bis-chelate was studied by quantum chemical density functional theory calculations (B3LYP/6-311++G(d, p)). The addition of the first pyridine molecule to the trans-position was found to be the most favorable channel for this two-stage process; the reaction is accompanied by a change in the spin state of the system. The transition between the potential energy surfaces of different multiplicity occurs at the first stage without considerable energy expenditure; the addition of the second pyridine molecule is barrierless.     

Synthesis and Crystal Structure of [Ni(II)(L)(py)_3]·(py)

1 INTRODUCTION Schiff bases and their metal complexes are useful reagents in organic synthesis[1], and they have exhi- bited some biological activities as anticancer and antitumor drugs[2]. The crystal structures and physi- cal and chemical properties of many Schiff bases and their transition metals complexes have been re- ported[3~5]. Further interest in the coordination che- mistry of nickel(II) arises from the role of these complexes in several catalytic reactions, such as electrocat…     

Syntheses and Crystal Structures of Two Trinuclear Iron(Ⅲ) Carboxylate Complexes: [Fe3(μ3-O)(μ-O2CEt)6(H2O)3]Cl.3H2O and [Fe3(μ3-O)(μ-O2CEt)6Py3]Cl(Py=pyridine)

Two new oxo-centered trinuclear iron complexes [Fe3(μ3-O)(μ-O2CEt)6(H2O)3]Cl.3H2O 1 and [Fe3(μ3-O)(μ-O2CEt)6Py3]Cl 2 were prepared in non-aqueous solvent and their crystal structures have been determined. Crystal 1 is monoclinic, space group P21/n, a=9.909(3), b=24.467(8), c=14.542(7)(), β=107.85(4)° V=3356(4)()3, Z=4, Mr=765.52, Dc=1.52 g/cm3, μ=14.28 cm-1, F(000)=1588 and R=0.059, Rw=0.071 for 3745 unique reflections with I>3σ(I). Crystal 2 belongs to the monoclinic system with space group C2/c, a=13.750(3), b=18.439(4), c=16.696(3)(), β=93.42(3)°, V=4226(3)()3, Z=4, Mr=894.73, Dc=1.41 g/cm3, μ=11.4 cm-1, F(000)=2322 and R=0.058, Rw=0.062 for 2272 unique reflections with I>3σ(I). The two structures contain the same trimetal framework in which three iron(Ⅲ) atoms form a nearly equilateral triangle with a μ3-oxygen atom in the centre.     

Protonation and acylation of the heterometallic complexes (μ-H)Os3(μ-O2CC5H4FeCp)(CO)10 and Fe{(μ-O2CC5H4)(μ-H)Os3(CO)10}2

The reactions of the heterometallic complexes (-H)Os₃(-O₂CC₅H₄FeCp)(CO)₁₀ (1) and Fe{(-O₂CC₅H₄)(-H)Os₃(CO)₁₀}₂ (2) with CF₃COOH, CF₃SO₃H, and AcCl were studied. The reaction of 1 with CF₃COOH involves interaction with the Cp ligands, protonation of the O atom of the bridging carboxylate group, and oxidative degradation of the complex. At low concentrations, CF₃SO₃H protonates the O atom of the bridging carboxylate group, while at high concentrations, degradation of the complex takes place. The reaction of complex 2with either CF₃COOH or low concentrations of CF₃SO₃H results in successive elimination of two [(-H)Os₃(CO)₁₀] cluster fragments due to protonation of the O atoms of the carboxylate groups. In the case of high CF₃SO₃H concentrations, the Os—Os bonds of both cluster fragments of 2 are also protonated to give the [Fe{(-O₂CC₅H₄)(-H)₂Os₃(CO)₁₀}₂]²⁺ dication. The Friedel—Crafts acylation of 1 takes place only when a large excess of AcCl and AlCl₃ is used to give two new complexes, (-H)Os₃(-O₂CC₅H₄FeC₅H₄C(O)CH₃)(CO)₁₀ and (-H)Os₃(-O₂CC₅H₃C(O)CH₃FeCp)(CO)₁₀ in a 2 : 1 ratio.     

Quantum chemical calculations and the structure of Ni n (C2H2) complexes (n = 1–4)

Complexes of nickel atoms and small clusters with acetylene molecules are studied within the density functional theory. A trend toward the predominant formation of structures with bridge hydrogen atoms is observed in reactions between Ni _n and acetylene with rising n.