Polynuclear Co<Superscript>II,III</Superscript> compounds containing pivalate and hexafluoroacetylacetonate anions in the ligand shell and their heterospin complexes with nitroxides

The reaction of cobalt(II) bis(hexafluoroacetylacetonate) (Co(hfac)₂) with polynuclear Co^II or Co^II,III pivalates, [Na₂Co₄(OH)₂(Piv)₈(EtOH)₄], [Co₂(H₂O)(Piv)₄(HPiv)₄], and [Co^III ₂Co^II ₄(O)₂(Piv)₁₀(H₂O)(THF)₃]·1.5THF (Piv is pivalate), affords the previously unknown cobalt compounds containing coordinated Piv and hfac anions in the ligand shell, viz., the dinuclear complex [Na₂Co₂(hfac)₄(Piv)₂(Me₂CO)₄], the tetranuclear complex [Co₄(Piv)₄(hfac)₂(OH)₂(HPiv)₄]·HPiv, and the tetradecanuclear complex [Co^III ₄Co^II ₁₀(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2HPiv·2H₂O·3C₇H₁₆, respectively. The tetradecanuclear complex has an unusual ability to precipitate nitroxides from solution, due to which the following new heterospin crystalline solids were synthesized: [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(H₂O)₂(HPiv)₂]·2NIT-Me·2HPiv·C₆H₁₄, [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2NIT-Et·2CHCl₃, [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2NIT-Ph·2C₆H₁₄, [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2L¹·2CH₂Cl₂, and [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄]·2L²·C₆H₁₄, where NIT-Me, NIT-Et, and NIT-Ph are 2-imidazoline nitroxides, L¹ is 3-imidazoline nitroxide, and L² is di-tert-butyl nitroxide. The X-ray diffraction study showed that the efficient binding of nitroxides is provided by the specific arrangement of the μ₃-OH groups in the [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(HPiv)₄] molecule, which is spatially complementary for the formation of numerous hydrogen bonds with the nitroxide moiety. The coordination of the nitroxides by terminal cobalt ions is impossible because this would lead to the impermissible spatial overlap of the atoms of the tetradecanuclear moiety and the nitroxide. The spatial characteristics of only NIT-H containing the H atom in position 2 of the 2-imidazoline ring are suitable for the direct coordination of the nitroxide, which made it possible to synthesize the complex [Co₁₄(Piv)₁₀(hfac)₄(OH)₁₄(O)₂(H₂O)₄(NIT-H)₂]·4HPiv·2H₂O.     

Crystal structure of polynuclear pivalate Ni(II) complexes with butanediol

Using single crystal X-ray diffraction the structure of polynuclear [Ni₆(OH)₄(Piv)₇(HOC₄H₈O)(HPiv)₄], {K₄[Ni₁₂(CO₃)₂(Piv)₁₆(OH)₈(HOC₄H₈OH)₂]}HPiv, {[Ni₆(OH)₄(Piv)₆(HOC₄H₈O)(Me₂CO)(HOC₄H₈OH)₂]₄×(Piv)₄}, and {K[Ni₂L₂(Piv)₃]}_∞ complexes, where HOC₄H₈OH is 1,4-butanediol, HPiv is pivalic acid, and L is the anion of nitroxyl radical 2,2,5,5-tetramethyl-4-(3′,3′,3′-trifluoro-2′-oxy-1′-propenyl)-3-imidazolin-1-oxyl is determined.     

Exchange coupling in polynuclear nickel(II) complexes with pivalate and hexafluoroacetylacetonate ligands: a quantum chemical analysis

The electronic structures of polynuclear different-ligand nickel(ii) complexes [K₂Ni₆Piv₇(hfac)₃(OH)₄(HPiv)₂(Me₂CO)₂], [Ni₆Piv₄(hfac)₄(OH)₄(Me₂CO)₄], and [Ni₈Piv₁₀(hfac)₂(OH)₂(MeO)₂(MeOH)₂(HPiv)₂] were studied within the framework of the DFT approach. For each complex, the isotropic exchange parameters for all pairs of paramagnetic centers were calculated. Based on the results obtained, models for Heisenberg-Dirac-van Vleck exchange interaction (with minimal number of parameters) were proposed, which can be used to describe the magnetic properties of the compounds under study.     

Polynuclear Ni<Superscript>II</Superscript> and Co<Superscript>II</Superscript> hexafluoroacetylacetonates

Hydrolysis of [M₄(hfac)₄(MeO)₄(MeOH)₄] (М = Сo, Ni and hfac is hexafluoroacetylaceton ate) is a convenient way of obtaining polynuclear complexes [Ni₇(hfac)₆(OH)₈(H₂O)₆]?2H₂O, [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₈]?2H₂O?2MePh, [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₄(Me₂CO)₄]?3PhMe, and [Co₁₂(hfac)₁₀(OH)₁₄(H₂O)₆(Me₂CO)₂]?2H₂O?2Me₂CO, whose structures were confirmed by X-ray analysis.     

Heterospin complexes of polynuclear Ni<Superscript>II</Superscript> compounds containing hexafluoroacetylacetonate and pivalate ligands with nitroxides

The heterospin mixed-ligand complex [Ni₆(OH)₄Piv₄(hfac)₄(NIT-Ph)₂] (1) (NIT-Ph is 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide, hfac is hexafluoroacetylacetonate, and Piv is pivalate) was synthesized. The method for the synthesis of complex 1 is based on the replacement of acetone molecules in the hexanuclear complex containing the hexafluoroacetylacetonate and pivalate ligands [Ni₆(OH)₄Piv₄(hfac)₄(Me₂CO)₄] by NIT-Ph molecules. Two monodentate NIT-Ph molecules replace four acetone molecules, because the coordination of the O atom of the nitroxide group results in the blocking of one of the positions in the coordination environment of Ni^II the access to which is hindered by the phenyl ring of NIT-Ph. As a result, these ions are in a square-pyramidal environment unusual of Ni^II. In the low-temperature range, the dependence of the magnetization of 1 on the magnetic field is described by the Brillouin function. The reaction of [Ni₆Piv₄(hfac)₄(OH)₄(Me₂CO)₄] with the nitronyl nitroxide radicals 4,4,5,5-tetramethyl-2-(4-pyridyl)-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide (NIT-p-Py) or 4,4,5,5-tetramethyl-2-(1-methyl-1H-imidazol-5-yl)-4,5-dihydro-1H-imidazol-1-oxyl 3-oxide (NIT-Iz) containing the pyridine or 1-methylimidazol-5-yl substituent, respectively, in the side chain is accompanied by the decomposition of the polynuclear fragment and affords the mononuclear complexes Ni(hfac)₂(NIT-p-Py)₂ and Ni(hfac)₂(NIT-Iz)₂, respectively. The reaction of 4,4,5,5-tetramethyl-2-(1-methyl-1H-imidazol-5-yl)-4,5-dihyd-ro-1H-imidazol-1-oxyl (Im-Iz), which is the imine analog of NIT-Iz, with [Ni₆Piv₄(hfac)₄(OH)₄(Me₂CO)₄] afforded the decanuclear complex [Ni₁₀(OH)₈Piv₄(hfac)₈(Im-Iz)₂(H₂O)₆]. The molecular and crystal structures of all heterospin compounds were determined, and the magnetic properties of all compounds were investigated in the 2–300 K temperature range.     

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.     

New Nanostructured Materials: Synthesis of Dodecanuclear NiII Complexes and Surface Deposition Studies

Microwave‐assisted synthesis has been used to obtain the family of dodecanuclear Ni^II complexes [Ni₁₂(NO₃)(MeO)₁₂(MeC₆H₄CO₂)₉(MeOH)₁₀(H₂O)₂][ClO₄]₂ ( 1 ), [Ni₁₂(NO₃)(MeO)₁₂(BrC₆H₄CO₂)₉(MeOH)₁₀(H₂O)₂][ClO₄]₂ ( 2 ), [Ni₁₂(CO₃)(MeO)₁₂(MeC₆H₄CO₂)₉(MeOH)₁₀(H₂O)₂]₂[SO₄] ( 3 ) and [Ni₁₂(NO₃)(MeO)₁₂(MeC₆H₄CO₂)₉(MeOH)₈(H₂O)₇][NO₃]₂ ( 4 ). They contain three {Ni₄O₄} cubane units which template around a central μ₆ anion, either NO₃^? or CO₃^2?. Their magnetic properties have been studied by superconducting quantum interference device (SQUID) magnetometry and high‐field EPR measurements. The nanostructuration of the Ni₁₂ species on mica surfaces is studied by AFM and grazing‐incidence X‐ray diffraction, which reveal the formation of polycrystalline thin layers.     

Structures of cerium manganese pivalates

The Ce,Mn mixed-metal polynuclear compounds [Ce ₃Mn₆(O)₅(OH)₃Piv₁₂Cl₂(THF)₃]·2THF, [Ce₃Mn₈(O)₈Piv₁₆Cl₂(HPiv)₂]·C₇H₁₆, [Ce₁₀Mn₄(O)₆(OH)₁₂Piv₁₆Cl₂(THF)₂]·2THF·2H₂O, [CeMn₁₁Cl₃(O)₈Piv₁₅(H₂O)]·CH₂Cl₂, and [CeMn₈(O)₈Piv₁₂(HPiv)₂(THF)₂] were prepared and structurally characterized. The possibility of synthesizing p,d,f-heterospin complexes by replacing coordinated THF molecules by nitroxide molecules was exemplified by the reaction of [Ce₃Mn₆(O)₅(OH)₃Piv₁₂Cl₂(THF)₃]·2THF with nitronyl nitroxides (NIT-R is 2-R-4,4,5,5-tetramethyl-24midazoline-l-oxyl 3-oxide; R is Me or 4-Py). The X-ray diffraction study of these complexes showed that [Ce₃Mn₆(O)₅(OH)₃Piv₁₂Cl₂(HPiv)(NIT-Me)₂] and [CeMn₈(O)₈Piv₁₂(NIT4-Py) ₄] · 2C₆H₁₄ have a molecular structure and [Ce₃Mn₆(O)₅(OH)₃-Piv₁₂Cl₂(NIT-Me)(H₂O)] is an infinite chain.     

Dodecanuclear Ni<Superscript>II</Superscript> complex containing pivalate and hexafluoroacetylacetonate ligands

A dodecanuclear complex [Ni₁₂Piv₁₀(hfac)₆(OH)₈(EtOH)₆]·C₆H₁₄ was isolated from various synthetic systems simultaneously containing Ni^II and the pivalate and hexafluoro-acetylacetonate anions. The structure of this complex was determined and the magnetic properties were investigated. The use of EtOH as the solvent or the presence of EtOH in the reagents is the decisive factor for the formation of this complex.     

Mononuclear pivalates of metals of the first transition series

The synthesis and structures of mononuclear Ni(II), Co(II), Mn(II), and Cu(II) pivalates isolated as complex salts NBu₄[M(Piv)₃] ((NBu₄)⁺ is tetrabutylammonium cation, Piv^– is pivalate anion) and polynuclear complexes [Ni₆(L)₂(HL)₂(Piv)₆(HPiv)₈], (NBu₄)₂[Co₄(Piv)₈(AcO)₂(H₂O)₄], NBu₄[Co₂(Piv)₅(H₂O)₂], and (NBu₄)₂[Cu₄(Piv)₈(AcO)₂(H₂O)₂] (L^2–, HL^–, and AcO^– is lactic acid dianion, lactic acid monoanion, and acetate anion, respectively) are discussed. The formation of the compounds is detected during the development of the synthesis of NBu₄[M(Piv)₃].     

New nickel(II) carboxylate-phosphonate cluster: Synthesis and structure

Dodecanuclear mixed-ligand complex [(??₂-Hmhp)₆Ni₁₂(??₃-OH)₄(??₆-O₃PPh)₄(??₂-Piv)₁₂] · 7.5MeCN · 1.5THF (I · 7.5MeCN · 1.5THF) was synthesized by the reaction of nickel(II) trimethylacetate [Ni₉(OH)₆(Piv)₁₂(HPiv)₄] (Piv^? is the pivalate anion) and 6-methyl-2-hydroxypyridine (Hmhp) with phenylphosphonic acid potassium salt (K₂O₃PPh). The structure of complex I is determined by X-ray diffraction analysis. The geometry of the metal framework of the isolated complex is determined by the structure forming phosphonate anion.     

Shift of stereochemical nonrigidity from coordination units to polymethylene fragments in heterospin copper(<Emphasis Type="SmallCaps">II</Emphasis>) hexafluoroacetylacetonate complexes with nitronyl nitroxide biradicals

The reactions of bis(hexafluoroacetylacetonato)copper(II) [Cu(hfac)₂] with the nitronyl nitroxide biradicals bis[4-(4,4,5,5-tetramethyl-3-oxide-1-oxyl-4,5-dihydro-1H-imidazol-2-yl)pyrazol-1-yl]alkanes (L⁶, L¹⁰, and L¹²) produced the framework heterospin complex [Cu(hfac)₂]₂L⁶ and the layer-polymeric heterospin complexes [Cu(hfac)₂]₂L¹⁰ and {[Cu(hfac)₂]₂L¹²} [Cu(hfac)₂(PrⁱOH)₂], respectively. In the solid state of these compounds, the stereochemical nonrigidity is manifested as a deformation of the polymethylene fragments-(CH₂)_n-. Dedicated to Academician G. A. Abakumov on the occasion of his 70th birthday. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1732–1741, September, 2007.     

Crystals of the CuII complex with nitronyl nitroxide and imino nitroxide exhibiting mechanical activity

As part of continuing studies of multispin compounds capable of exhibiting chemomechanical activity, a series of heterospin solids of the composition [Cu(hfac)₂L _x L′_2?x ], [Cu(hfac)₂L′], [Cu₂(Piv)₄L′₂]·0.5C₆H₁₄, and [Cu₂(hfac)₂(Piv)₂L′2], where hfac is the hexafluoroacetylacetonate anion, L is 4,4,5,5-tetramethyl-2-(1-methyl-1H-imidazol-5-yl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, L′ is the imino nitroxide analog of L, viz., 4,4,5,5-tetramethyl-2-(1-methyl-1H-imidazol-5-yl)-4,5-dihydro-1H-imidazole-1-oxyl, and Piv is the 2,2-dimethylpropionate anion, were synthesized and characterized. The packing of the synthesized crystals of the solid solutions [Cu(hfac)₂L _x L′_2-x ], where L predominates, is similar to that for [Cu(hfac)₂L₂], and these crystals are able to undergo chemomechanical motion. On the contrary, the crystals of [Cu(hfac)₂L _x L′_2?x ], where L′ predominates, have structural parameters similar to those of [Cu(hfac)₂L′₂] and do not exhibit thermally activated or photoactivated chemomechanical activity.     

Manganese (III) fluoride as a new synthon in Mn cluster chemistry

The syntheses and structures of five new Mn³⁺ clusters [Mn₂₆O₁₇(OH)₈(OMe)₄F₁₀(Bta)₂₂(MeOH)₁₄(H₂O)₂] (1), [Mn₁₀O₆(OH)₂(Bta)₈(py)₈F₈] (2), {NHEt₃}₂[Mn₃O(Bta)₆F₃] (3), [Mn₈O₄(OMe)₂(Me₂Bta)₆F₈(Me₂BtaH)(MeOH)₈] (4), and [Mn₁₃O₁₂(Me₂Bta)₁₂F₆(MeOH)₁₀(H₂O)₂] (5), are reported, thereby demonstrating the utility of MnF₃ as a new synthon in Mn cluster chemistry.     

One-pot synthesis of an unusual manganese–lanthanide–ferrocene cluster: A combination of d-, f-metals and an organometallic fragment

Reaction of the preformed cluster [Mn₆O₂(Piv)₁₀(4-Me-py)_2.5(PivH)_1.5] with Nd(NO₃)₃.6H₂O, N-butyldiethanolamine (bdeaH₂) and ferrocene-1,1′-dicarboxylic acid (fcdcH₂) resulted in the formation of the first 3d–4f complex incorporating organometallic ferrocene [Mn₄Nd₄(OH)₄(fcdc)₂(Piv)₈(bdea)₄]·H₂O; we report the X-ray structure and preliminary magnetic studies of this high-nuclearity cluster.     

Carboxylate clusters with the M<Subscript>4</Subscript>O<Subscript>4</Subscript> cubane-like core: pivalate cocrystal containing Co<Superscript>II</Superscript> and Ni<Superscript>II</Superscript>

Joint thermolysis of the dinuclear pivalate complexes M₂(μ-H₂O)(μ-Piv)₂(Piv)₂(HPiv)₄ (M = Co (1) and Ni (2), Piv^- is the pivalate anion), in decane at 174 °C at the reactant ratio 1: 1 followed by treatment of the dry thermolysis product with methanol afforded crystals of a new cocrystallization product of the molecules containing the heterometallic cubane-like core M₄(Co,Ni)O₄. According to the X-ray diffraction data and the results of magnetic measurements, inductively coupled plasma atomic emission spectrometry (ICP-AES), and investigations of the solid-state thermal decomposition products, the isolated cocrystallization product has the general formula [Co_1.6Ni_2.4(μ₃-OMe)₄(μ₂-Piv)₂(pg² -Piv)₂(MeOH)₄] ·4MeOH (3·4MeOH). Thermolysis of the crystals of the solvate 3·4MeOH is a destructive process accompanied by the intramolecular redox reaction. A mixture of metallic Ni and cobalt oxide (CoO) are the final solid decomposition products of 3 · 4MeOH in an argon atmosphere, whereas a mixture of the phases NiO, Co₃O₄, and NiCo₂O₄ is formed in air.     

Macrocyclic‐ligand Induced Synthesis of Aryl Ethynides with Divergent Silver(I) Clusters

Two structurally characterized metal‐cluster‐centered supramolecular architectures named [Ag₈(1,2‐(C ≡ C)₂‐C₆H₄ )( Py[6] )(CF₃CO₂ )₆] · 2.5MeOH ( 1 ) and [Ag₁₂(1,2,4,5‐(C ≡ C)₄C₆H₂ )( Py[6] )₂(CF₃SO₃ )₈]·4MeOH ·3H₂O ( 2 ) are synthesized through the interaction with a bowl‐shaped macrocyclic ligand Py[6] . Particularly, two dissimilar silver(I) clusters are resulted in 2 within the structure under the influence of the macrocyclic ligand Py[6] . Such dissimilarity of the silver(I) cluster is also reflected on the structural and photophysical differences between 1 and 2 .     

New approach to the synthesis of polynuclear heterometallic pivalates with iron and manganese atoms

New hexanuclear Fe(III)–Mn(II, III) pivalates [Fe₂ ^III Mn₄ ^II(O)₂(Piv)₁₀(HPiv)₄] (I) or [Fe₄ ^III Mn₂ ^III(O)₂(Piv)₁₂(CH₂O₂)(HPiv)₂] · Et₂O (II) are synthesized using the solid-state thermolysis of [Fe₂Mn(O)(Piv)₆(HPiv)₃] (90°С). Complexes I and II differ by the ratio of iron and manganese ions, which depends on the atmospheric composition during thermolysis. The structures of compounds I and II are determined by X-ray diffraction studies. According to the parameters of the Mössbauer spectrum, complex I contains the Fe³⁺ ions in the high-spin state in the octahedral environment of oxygen atoms.     

Unusual magnetic behavior of the new supramolecular ensemble [Ni2L4]2·[NiCl2(LH)2(MeCN)2]·4MeCN (LH is 2-mercaptobenzimidazole)

The diamagnetic dinuclear complex Ni₂L₄ was synthesized by the reaction of NiCl₂·6H₂O with 2-mercaptobenzimidazole (LH) in ethanol in the presence of Et₃N. The solid-state reaction (reagent ratio Ni: LH = 1: 2) followed by recrystallization of the reaction product from a MeCN-THF mixture afforded crystals of the associate [Ni₂L₄]₂·[NiCl₂(LH)₂(MeCN)₂] containing four acetonitrile solvate molecules. Crystals of 2·4MeCN exhibit ferromagnetic properties at helium temperatures. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2101–2105, December, 2006.     

Capping [H<Subscript>8−n</Subscript>Ni<Subscript>42</Subscript>C<Subscript>8</Subscript>(CO)<Subscript>44</Subscript>]<Superscript>n−</Superscript> (n = 6, 7, 8) Octa-carbide Carbonyl Nanoclusters with [Ni(CO)] and [CuCl] Fragments

The reactions of [Ni₁₆(C₂)₂(CO)₂₃]^4? and [Ni₃₈C₆(CO)₄₂]^6? with CuCl afforded mixtures of the previously reported [HNi₄₂C₈(CO)₄₄(CuCl)]^7? bimetallic octa-carbide cluster and the new [HNi₄₃C₈(CO)₄₅]^7? and [HNi₄₄C₈(CO)₄₆]^7? homo-metallic octa-carbides. The three species have very similar properties resulting always in co-crystals such as [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·6.5MeCN (x = 0.14) (86% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 14%[HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?) and [NMe₄]₇[HNi_42+2xC₈(CO)_44+2x(CuCl)_1?x]·5.5MeCN (x = 0.30) (70% [HNi₄₂C₈(CO)₄₄(CuCl)]^7?, 30% [HNi₄₃C₈(CO)₄₅]^7?/[HNi₄₄C₈(CO)₄₆]^7?). The new homo-metallic octa-carbides can be obtained free from the Ni–Cu octa-carbido cluster by reacting [Ni₁₀(C₂)(CO)₁₆]^2? in thf with a stoichiometric amount of CuCl, and crystals of [NMe₄]₆[H₂Ni_43+xC₈(CO)_45+x]·6MeCN (x = 0.72), which contain [H₂Ni₄₄C₈(CO)₄₆]^6? (72%) and [H₂Ni₄₃C₈(CO)₄₅]^6? (28%), have been obtained. Despite the different charges and compositions, these anions display almost identical structures, which are also closely related to those previously reported for the bimetallic Ni–Cd octa-carbido clusters [Ni_42+xC₈(CO)_44+x(CdCl)]^7? and [HNi_42+xC₈(CO)_44+x(CdBr)]^6?. Indeed, all these clusters are based on the same Ni₄₂C₈ cage decorated by miscellaneous [CdX]⁺ (X = Cl, Br), [CuCl] and [Ni(CO)] fragments.