Tetranuclear cobalt trimethylacetate Co4(μ3-OH)2(μ-OOCBut)6(C4H6N2O)4 containing coordinated 3-methyl-5-pyrazolone

We found that the reaction of the compound obtained by alloying hydrous cobalt(II) acetate and pivalic acid with 3-methyl-5-pyrazolone in refluxing hexane produces the tetranuclear complex Co₄(μ₃-OH)₂(μ-OOCBu^t)₆·(C₄H₆N₂O)₄·2HOOCBu^t (complex 3). The complex has been structurally characterized using single-crystal X-ray diffraction     

A hexanuclear cobalt(III) complex containing the pseudocubane fragment [Co4(μ4-O)2(μ3-O)2] in its metal framework and a solvated dibenzyl ether molecule

Room-temperature oxidation of a mixture of the complex (Co^II)₃(μ-OOCBu _t )₆(NEt₃)₂ and dibenzyl ether (DBE) with atmospheric oxygen in dichloromethane-benzene (4: 1) gave the hexanuclear complex [(Co^III)₆(μ₄-O)₂(μ₃-O)₂(μ-OOCBu ^t )₉(OH)₂(HOOCBu ^t )](HNEt₃) · 0.5DBE · C₆H₆ (I) as the major reaction product. According to X-ray diffraction data, the metal framework of complex I contains the pseudocubane fragment [Co₄(μ₄-O)₂(μ₃-O)₂] linked with two “peripheral” cobalt(III) ions. The possibility of using complex I as an intermediate catalyst for liquid-phase oxidation of DBE as well as the conformational changes in the DBE molecule due to its adaptation to the metal complexes are discussed.     

Transformations of high spin MnII and FeII polymeric pivalates in reactions with pivalic acid and o-phenylenediamines

The thermolysis and reactions of the polymeric high spin Mn^II and Fe^II complexes [Mn(μ-OOCBu^t)₂(HOEt)]_n (1) and [Fe(μ-OOCBu^t)₂]_n (3) with pivalic acid and o-phenylenediamines 1,2-(NH₂)₂C₆H₂R₂ (R = H or Me) were studied. The synthesis of compound 1 performed with a deficiency of pivalate anions affords the antiferromagnetic chloropivalate polymer { (MeCN)(HOOCBu^t)(H₂O)Mn₅Cl(OH)(OOCBu^t)₈·MeCN}_n. The reaction of 1 with an excess of pivalic acid produces the antiferromagnetic polymer [Mn₄(OOCBu^t)₈(HOOCBu^t)₂]_n. The analogous reaction of pivalic acid with polymer 3 gives the mononuclear complex Fe(η ¹-OOCBu^t)₂(η¹-HOOCBu^t)₄ containing the high spin iron(II) atom as the major product. Study of the reactions of 3 with a deficiency (<1: 1) and an excess (>1: 1) of diamines demonstrated that the polymer {[(η²-(NH₂)₂C₆H₄)₂Fe(μ-OOCBu^t)₂][Fe₂(μ-OOCBu^t)₄] · · 2MeCN}_n is generated as the major product in the former case, whereas the mononuclear complexes Fe(η¹-OOCBu^t)₂[η¹-(NH₂)₂C₆H₄]₄ and Fe(η¹-OOCBu^t)₂[η²-(NH₂)₂C₆H₂Me₂][η¹-(NH₂)₂C₆H₂Me₂]₂ are predominantly obtained in the latter case. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 779–792, May, 2006.     

Thermolysis of binuclear heterometallic pivalate with Pd(II)-Ce(III) metal core in dibenzyl ether

A reaction between palladium(II) acetate and aqueous cerium(III) acetate in acetic acid with subsequent boiling in benzene with excess pivalic acid is found to yield the complex Pd(μ-OOCBu^t)₄Ce(OOCBu^t)(HOOCBu^t)₃ (1). The liquid-phase thermolysis of complex 1 in dibenzyl ether (190°C) leads to the formation of the tetranuclear complex [Pd(μ-OOCBu^t)₄Ce(HOOCBu^t)]₂(μ-OOCBu^t)(μ-OH₂) (2). The structure of the synthesized complexes is established by X-ray diffraction.     

New polynuclear cobalt trimethylacetate complexes: synthesis and structure

Extraction of polymer (1), formed in the reaction of CoCl₂ with KOOCBu^t, with boiling hexane gives crystals of hexamer Co₆(μ₃-OH)₂(OOCBu¹)₁₀(HOOCBu¹)₄ (2). According to data of X-ray study, four Co¹¹ atoms in the hexanuclear molecule2 have an octahedral ligand environment and two Co¹¹ atoms have a tetrahedral one. Dissolution of polymer1 in EtOH results in its splitting into Co₄(μ₃-OH)₂(OOCBu¹)₆(HOEt)₆ tetramers (3). In molecule3, two asymmetric dimeric (η²-OOCBu^t)(EtOH)Co(μ-OOCBu^t)Co(HOEt)₂ fragments are bound by two tridentate bridging OH groups. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1773–1778, September, 1999.     

Thermal transformations of complexes Co2(μ-OOCBut)4(NEt3)2 and Co3(μ-OOCBut)2(μ-OOCBut)4(NEt3)2

The features of thermal transformations of trimethylacetatocobalt complexes Co₂(μ-OOCBu^t)₄(NEt₃)₂ and Co₃(μ-OOCBu^t)₂(μ-OOCBu^t)₄(NEt₃)₂ with attendant geometric alterations are considered as dependent on temperature on the basis of single-crystal X-ray diffraction, magnetochemical, and thermochemical investigations.     

Formation of an Ni7(μ3-OH)6(η-OOCBu t )6(μ3-OOCBu t )2(Hdmpz)6 cluster during the thermolysis of binuclear complex Ni2(μ-OOCBu t )4(Hdmpz)2 (Hdmpz = 3,5-dimethylpyrazole)

Cluster Ni₇(μ₃-OH)₆(OOCBu ^t )₈(Hdmpz)₆ was found to form as a result of the thermal destruction of complex Ni₂(μ-OOCBu ^t )₄(Hdmpz)₂ at 190°C. The cluster was characterized using X-ray crystallography.     

On the nature of the chemical bond in heterobimetallic palladium(II) complexes with divalent 3<Emphasis Type="Italic">d</Emphasis> metals

The complex Pd(μ-OOCMe)₄Cu(OH₂) · 2Pd₃(μ-OOCMe)₆ was synthesized and characterized by X-ray crystallography. In the heterometallic moiety of this complex, the Pd^II and Cu^II atoms are at an extraordinary short distance (2.521(3) Å). DFT quantum-chemical calculations of the geometric and electronic structure of a series of heterobinuclear paddlewheel complexes Pd^IIM^II(μ-OOCMe)₄L (M = Zn^II, Ni^II, Cu^II, Co^II, Fe^II; L = OH₂ and NCH) and their formate analogues Pd^IIM^II(μ-OOCH)₄L (M = Zn^II, Ni^II, Fe^II) showed that the extraordinary short Pd?M distance in all these complexes is caused only by the tightening effect of carboxylate bridges rather than by the metal-metal bond. The direct Pd-M interaction becomes possible only after removal of electrons from the antibonding orbitals and formation of oxidized complexes of the [Pd^III(μ-OOCMe)₄Ni^III]²⁺ type.     

2‐Amino‐5‐(2‐pyridyl)‐thiadiazole as Bidentate Ligand

The amino substituted bidentate chelating ligand 2‐amino‐5‐(2‐pyridyl)‐1,3,4‐thiadiazole (H₂ L ) was used to prepare 3:1‐type coordination compounds of iron(II), cobalt(II) and nickel(II). In the iron(II) perchlorate complex [Fe^II(H₂ L )₃](ClO₄)₂·0.6MeOH·0.9H₂O a 1:1 mixture of mer and fac isomers is present whereas [Fe^II(H₂ L )₃](BF₄)₂·MeOH·H₂O, [Co^II(H₂ L )₃](ClO₄)₂·2H₂O and [Ni^II(H₂ L )₃](ClO₄)₂·MeOH·H₂O feature merely mer derivatives. Moessbauer spectroscopy and variable temperature magnetic measurements revealed the [Fe^II(H₂ L )₃]²⁺ complex core to exist in the low‐spin state, whereas the [Co^II(H₂ L )₃]²⁺ complex core resides in its high‐spin state, even at very low temperatures.     

Homo- and heterometallic trinuclear nickel(ii) and cobalt(ii) pivalate complexes

The reaction of the dinuclear complex Co₂(bpy)₂(OOCBu^t)₄ with the tetranuclear complex Ni₄(₃-OH)₂(OOCBu^t)₆(EtOH)₆ afforded the trinuclear heterometallic complex M₃(bpy)₂(₃-OH)(-OOCBu^t)₄(OOCBu^t) (6) (M = Ni, Co; Ni : Co = 1.2 : 1) in which two metal atoms are in an octahedral environment and one metal atom is in a tetrahedral environment. The reaction of 2,2"-bipyridine with Co₄(₃-OH)₂(OOCBu^t)₆(HOEt)₆ (reagent ratio was 2 : 1) or the reaction of bpy with Co₈(₄-O)₂( _n -OOCBu^t)₁₂ (reagent ratio was 4 : 1) produced a homometallic analog of 6, viz., the trinuclear cluster Co₃(bpy)₂(₃-OH)(-OOCBu^t)₄(OOCBu^t) (8). The reaction of 1,10-phenanthroline (phen) with the [Co(OH) _n (OOCBu^t)_2–n ] _x polymer gave the analogous trinuclear cluster (phen)₂Co₃(₃-OH)(₂-OOCBu^t)₄(¹-OOCBu^t). Compounds 6 and 8 exhibit antiferromagnetic spin-spin exchange interactions.     

Binuclear Copper(II) Complexes with Robsori-Type Ligands. Synthesis,characterization, crystal structure,and magnetic properties

Three binuclear copper(II) complexes, [Cu₂(μ-L)(μ-N₃)](ClO₄)2′ 1-5 EtOH (1), [Cu₂(μ-L)(μ-MeO)(ClO₄)]-ClO₄ - EtOH ( 2 ) and [Cu₂(μ-L)(μ-C₃H₃N₂)](ClO₄)₂ · 2H₂O, ( 3 ) where L is the pentadentale bridging ligand derived from 5-(tert-butyl)-2-hydroxybenzene-1, 3-dicarbaldehyde bis(benzoylhydrazone) ( HL ) were synthesized and characterized. The crystal-structure determination of complex 2 provided the following crystal data: monoclinic, space group P2₁}/a, a = 11.412(2), b = 24.509(4), c = 14.833(4) Å, β = 104.41(2)°, K = 4018(3) ų, Z = 4. The structure shows that the Cu^II ions are bridged by the endogenous phenolato O-atom and by an exogenous bridge CH₃O^?. The analysis of variable-temperature magnetic susceptibility data (4-300 K.) indicates that there is an antiferromagnetic interaction between the Cu^II ions in these complexes with an exchange parameter (2J) of ?119.1 cm^?1 for complex 1 and ?361.8 cm^?1 for complex 3 . The effect of some exogenous bridging ligands on magnetic coupling for this type of complex is suggested.     

Lanthanide(II) Complexes of the Dihydrotriazinido Ligand [N{C(Ph)=N}2C(tBu)Ph]−

The potassium dihydrotriazinide K(L^Ph,tBu) ( 1 ) was obtained by a metal exchange route from [Li(L^Ph,tBu)(THF)₃] and KOtBu (L^Ph,tBu = [N{C(Ph)=N}₂C(tBu)Ph]). Reaction of 1 with 1 or 0.5 equivalents of SmI₂(thf)₂ yielded the monosubstituted Sm^II complex [Sm(L^Ph,tBu)I(THF)₄] ( 2 ) or the disubstituted [Sm(L^Ph,tBu)₂(THF)₂] ( 3 ), respectively. Attempted synthesis of a heteroleptic Sm^II amido‐alkyl complex by the reaction of 2 with KCH₂Ph produced compound 3 due to ligand redistribution. The Yb^II bis(dihydrotriazinide) [Yb(L^Ph,tBu)₂(THF)₂] ( 4 ) was isolated from the 1:1 reaction of YbI₂(THF)₂ and 1 . Molecular structures of the crystalline compounds 2 , 3· 2C₆H₆ and 4· PhMe were determined by X‐ray crystallography.     

Synthesis and characterization of CuII and CoII complexes derived from 2,4,6-tri-(2-pyridyl)-1,3,5-triazine (TPT) by chemical and tribochemical reactions

Four Cu^II and Co^II complexes–[Cu(L₁)Cl₂(H₂O)]3/2H₂O · 1/2EtOH, [Cu(L₁)₂Cl₂]6H₂O, [Co(L₁)Cl₂]3H₂O · EtOH, and [Co₂(L₁)(H₂O)Cl₄]1.5H₂O · EtOH (L₁ = 2,4,6-tri(2-pyridyl)-1,3,5-triazine; TPT)–were synthesized by conventional chemical method and used to synthesize another four metal complexes–[Cu(L₁)I₂(H₂O)]6H₂O, [Cu(L₁)₂I₂]6H₂O, [Co(L₁)I(H₂O)₂]I · 2H₂O, and [Co₂(L₁)I₄(H₂O)₃]–using tribochemical reaction, by grinding it with KI. Substitution of chloride by iodide occurred, but no reduction for Cu^II or oxidation of Co^II. Oxidation of Co^II to Co^III complexes was only observed on the dissolution of Co^II complexes in d₆-DMSO in air while warming. The isolated solid complexes (Cu^II and Co^II) have been characterized by elemental analyses, conductivities, spectral (IR, UV-Vis, ¹H-NMR), thermal measurements (TGA), and magnetic measurements. The values of molar conductivities suggest non-electrolytes in DMF. The metal complexes are paramagnetic. IR spectra indicate that TPT is tridentate coordinating via the two pyridyl nitrogens and one triazine nitrogen forming two five-membered rings around the metal in M : L complexes and bidentate via one triazine nitrogen and one pyridyl nitrogen in ML₂ complexes. In binuclear complexes, L is tridentate toward one Co^II and bidentate toward the second Co^II in [Co₂(L₁)Cl₄]2.5H₂O · EtOH and [Co₂(L₁)I₄(H₂O)₃]. Electronic spectra and magnetic measurements suggest a distorted-octahedral around Cu^II and high-spin octahedral and square-pyramidal geometry around Co^II.     

Synthesis,Structure and Magnetic Properties of a Cyano‐bridged Dinuclear Compound fac‐{[FeIII(pzTp)(CN)2(μ‐CN)] CuII(TPyA)}·Et2O·ClO4 (pzTp = tetrakis(pyrazolyl)borate)

The reaction of tricyanometallate precursor, (Bu₄N)[(pzTp)Fe(CN)₃] with Cu(ClO₄)₂·6H₂O in the presence of the tetradentate ligand tris(2‐pyridylmethyl)amine (TPyA) afford the dinuclear compound fac‐{[Fe^III(pzTp)(CN)₂(μ‐CN)]Cu^II(TPA)}·Et₂O·ClO₄ ( 1 ) (pzTp = tetrakis(pyrazolyl)borate). The molecular structure was determined by single‐crystal X‐ray diffraction. In compound 1 , the Fe^III ion is coordinated by three cyanide carbon atoms and three nitrogen atoms of pzTp anions. Whereas, the Cu^II ion is surrounded by one cyanide nitrogen atom and four nitrogen atoms from the TPyA ligand. Magnetic measurements indicate the intramolecular ferromagnetic coupling is observed for compound 1 , and it has S = 1 ground states.     

Novel Trinuclear MnII/MnII/MnII Complexes – Crystal Structures and Catalytic Properties

The trinuclear manganese(II) complexes [Mn₃(L¹)₂(μ‐OAc)₄]·2Et₂O {HL¹ = (1‐hydroxy‐4‐nitrobenzyl)((2‐pyridyl)methyl)((1‐methylimidazol‐2‐yl)methyl)amine} ( 1·2EtOH ), [Mn₃(L²)₂(μ‐OAc)₄] {HL² = ((1‐methylimidazol‐2‐yl)methyl)(1‐hydroxybenzyl)amine} ( 2 ) and [Mn₃(L³)₂(μ‐OAc)₆] {L³ = bis(1‐methylimidazol‐2‐yl)methanone} ( 3 ) were synthesized. The compounds were characterized by X‐ray crystallography, mass spectrometry, IR, UV‐vis spectroscopy, and elemental analysis. The manganese atoms in 1 and 2 are bridged by phenol moieties of the ligands and acetates. In 3 they are only bridged by acetates in a mono‐ and bi‐dentate way. The resulting Mn···Mn distances are 3.233(1) Å ( 1 ), 3.364(1) Å ( 2 ) and 3.643(7) Å ( 3 ). In the present compounds different limiting cases for the phenomenon of the carboxylate shift are realized. Besides symmetric mono‐ and bi‐dentate bridging an unusual intermediate is also observed. 1·2EtOH is the first example of a trinuclear model for the OEC that shows catalase activity. Furthermore it was characterized by temperature dependent magnetic susceptibility measurements and a total spin ground state of S_t = 5/2 was found. The results for 1 reveals antiferromagnetic coupling between the central and the terminal manganese ions, with J = ?1.2 cm^?1, g = 2.00 (fixed), χ_TIP = 150×10^?6 cm³mol^?1.     

Chemical design of heterometallic carboxylate structures with Fe3+ and Ag+ ions as a rational synthetic approach

Solid phase thermolysis of pivalate complex [Fe₃O(Piv)₆(HPiv)₃]Piv generates the [Fe₃O(Piv)₆]⁺ complex cation due to a deficiency of ligands in the coordination sphere of the metal ions. Crystallization of [Fe₃O(Piv)₆]⁺ from THF–EtOH leads to the heteroleptic complex [Fe₃O(Piv)₆(THF)(EtOH)(OH)] · 0.5 THF · 0.5 H₂O in 69% yield, while the reaction of [Fe₃O(Piv)₆]⁺ with AgNO₃ in toluene results in the complex [Fe₄Ag₄O₂(Piv)₁₂] · 2 PhMe with a rare combination of Fe^III and Ag^I atoms. Crystal structures of the two new complexes have been established.     

Untersuchung von Hydrolysereaktionen zum Aufbau von Eisen(III)‐Oxo‐Aggregaten

Investigation of the Hydrolytic Build‐up of Iron(III)‐Oxo‐Aggregates The synthesis and structures of five new iron/hpdta complexes [{Fe^III₄(μ‐O)(μ‐OH)(hpdta)₂(H₂O)₄}₂Fe^II(H₂O)₄]·21H₂O ( 2 ), (pipH₂)₂[Fe₂(hpdta)₂]·8H₂O ( 4 ), (NH₄)₄[Fe₆(μ‐O)(μ‐OH)₅(hpdta)₃]·20.5H₂O ( 5 ), (pipH₂)_1.5[Fe₄(μ‐O)(μ‐OH)₃(hpdta)₂]·6H₂O ( 7 ), [{Fe₆(μ₃‐O)₂(μ‐OH)₂(hpdta)₂(H₄hpdta)₂}₂]·py·50H₂O ( 9 ) are described and the formation of these is discussed in the context of other previously published hpdta‐complexes (H₅hpdta = 2‐Hydroxypropane‐1, 3‐diamine‐N, N, N′, N′‐tetraacetic acid). Terminal water ligands are important for the successive build‐up of higher nuclearity oxy/hydroxy bridged aggregates as well as for the activation of substrates such as DMA and CO₂. The formation of the compounds under hydrolytic conditions formally results from condensation reactions. The magnetic behaviour can be quantified analogously up to the hexanuclear aggregate 5 . The iron(III) atoms in 1 ‐ 7 are antiferromagnetically coupled giving rise to S = 0 spin ground states. In the dodecanuclear iron(III) aggregate 9 we observe the encapsulation of inorganic ionic fragments by dimeric{M₂hpdta}‐units as we recently reported for Al^III/hpdta‐system.     

One‐Pot Assembly of a New Mixed‐Valent Aggregate Based on Inorganic Polyoxometalate Ligands

Employing a “one‐pot” synthesis strategy, the reaction of Na₂WO₄·2H₂O, Na₂HAsO₄·7H₂O, FeCl₃·6H₂O, various Ln³⁺ ions, and hexamethylenetetramine (HMTA) in aqueous solutions with pH values ranging from 5.5 to 6.5 results in the isolation of polytungstoarsenate‐based iron aggregates, ‐K₈Na₁₄[HMTA]₄[(Fe^III₃Fe^II_0.25(OH)₃)(AsO₄)(AsW₉O₃₄)]₄·24H₂O ( 1 ) (HMTA = hexamethylenetetraamine). The polyoxoanion of 1 contains a mixed‐valent {Fe^III₁₂Fe^II(μ₃‐OH)₁₂(μ₄‐AsO₄)₄} cluster surrounded by four [B‐α‐AsW₉O₃₄]^9? units. It is the first polytungstatoarsenate‐based mixed‐valent {Fe^III₁₂Fe^II} aggregate and the largest iron cluster based on [AsW₉O₃₄]^9? ligands. The compound was characterized by elemental analyses, IR, UV/Vis absorption, and diffuse‐reflectance UV/Vis spectroscopy, TG analyses, XRPD, XPS and gel‐filtration chromatography. The electrochemical and electrocatalytical properties were also investigated. Crystal data for 1 , orthorhombic, Fddd, a = 28.156(6) Å, b = 36.003(7) Å, c = 42.126(8) Å, α = 90°, β = 90°, γ = 90°, Z = 8.     

Synthesis, structures, and magnetic properties of carboxylate-bridged trinuclear complexes based on low-spin manganese(III)/iron(III) building blocks

Four linear trinuclear transition metal complexes have been prepared and characterized. The complexes [M^II(MeOH)₄][Fe^III(L)₂]₂·2MeOH (M = Fe (1) or Ni (2)), [Co^II(EtOH)₂(H₂O)₂][Fe^III(L)₂]₂·2EtOH (3), and [Mn^II(phen)₂][Mn^III(L)₂]₂·4MeOH (4) (H₂L = ((2-carboxyphenyl)azo)-benzaldoxime, phen = 1,10-phenanthroline) possesses a similar syn–anti carboxylate-bridged structure. The terminal Fe(III) or Mn(III) ions are low spin, and the central M(II) ions are high spin. Magnetic measurements show that antiferromagnetic interactions were present between the adjacent metal ions via the syn–anti carboxylate bridges. The antiferromagnetic coupling between low-spin Fe(III) and Ni(II) is unusual, which has been tentatively assigned to the structural distortion of Fe(III).     

Synthesis,structure, and luminescent properties of two novel polynuclear complexes of 1,3-di(pyridin-2-yl)propane-1,3-dione

Two complexes, {[Cd₆(o-dppd)₂(μ²-Cl)₆(μ³-Cl)₂(DMF)₂(H₂O)₂Cl₂]·DMF·CH₃OH} _n (I) (DMF = N,N-dimethylformamide; o-dppdH = 1,3-di(pyridin-2-yl)propane-1,3-dione) and [Cu₄(o-dppd)₂(OAc)₄(OH)₂]·4H₂O (II), were synthesised and characterised by single-crystal X-ray diffraction, elemental analysis, IR, solid fluorescence and TGA. The results showed that complex I had a rodshaped polynuclear chain with hexacoordinating Cd atoms bridged by oxygen, μ²-Cl and μ³-Cl; complex II was a tetranuclear oligomer. In general, supramolecular architectures are constructed through hydrogen-bonding and π-π stacking interactions. I shows luminescence.