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The crystal and molecular structure of a polynuclear pivalate complex obtained by the interaction of ZrCl4 with pivalic acid is determined by X-ray diffraction analysis. The compound C71H124O28Zr4 crystallizes in a monoclinic crystal system. The crystal structure is refined in the nonstandard space group I2. The asymmetric part of the structure includes three Zr atoms, six pivalate ligands, and a bridging µ3-O oxygen atom, as well as disordered crystallization molecules of pivalic acid with an occupancy of 50% and benzene with an occupancy of 50%. The zirconium complex molecule is a tetranuclear cluster that contains three types of Zr atoms that differ in the ligand environment. A comparison of the results of the quantum chemical calculations of the model reaction of ZrCl4 with acetic acid with the published data on reactions of ZrCl4 with aliphatic acids shows the possibility of the formation of both mononuclear Zr(RCO2)4 and polynuclear clusters in this reaction, which is a new route for obtaining polynuclear zirconium clusters. The structure of the clusters formed depends on the steric properties of carboxylate ligands. [ABSTRACT FROM AUTHOR]

The review addresses the main approaches to desulfurization of hydrocarbon products by adsorption methods. Examples of the use of various supports (metal-organic frameworks, various porous carbons, silica, and alumina) for the removal of acidic sulfur components from gas and liquid hydrocarbons are presented. Modification of the supports with transition metals, oxides, salts, and complex compounds to remove hydrogen sulfide and thiols from hydrocarbon raw materials is substantiated. The environmental friendliness and lower energy consumption for the use of silica gel modified with Zn(II), Co(II), Ni(II), and Cu(II) carboxylates to refine hydrocarbon fuel are demonstrated. A comparison of the theoretical calculations (DFT) with experimental results attests to good agreement between the data. The choice of the parameters for silica gel surface modification with metal carboxylates is discussed, including pore size of the support, time and power of the ultrasonic treatment for the support impregnation with solutions of complexes, optimal concentration of transition metal complexes, effect of the geometry of complexes on their adsorption and on the absorption of acidic sulfur components, and so on. According to quantum chemical calculations and experimental results, metal sulfides are formed as the final products of reactions of both hydrogen sulfide and thiols with metal carboxylates. Zinc pivalate is proposed as the most promising modifier for silica, which not only efficiently removes sulfur impurities, but also gives rise to nontoxic zinc sulfide supported on silica gel. [ABSTRACT FROM AUTHOR]

The cadmium oxopivalate complex CdPiv2 ∙ Cd4OPiv6 has been synthesized and its thermodynamic characteristics have been studied using the Knudsen effusion technique with the mass spectral analysis of the gas phase. It has been found that vaporization of this complex proceeds congruently and the saturated vapor above it consists of molecules Cd2Piv4, Cd4Piv8, and Cd4OPiv6. The standard enthalpies of sublimation of these molecules have been determined; the standard enthalpy of vaporization of complex CdPiv2 ∙ Cd4OPiv6 and standard enthalpy of dissociation of the Cd4Piv8 molecule according to the second and third laws of the thermodynamics have been found to be = 297.0 ± 12.1 kJ/mol and = 133.2 ± 16.8 kJ/mol, respectively. It is shown that the oxopivalate cadmium complex can be used as a precursor in the MO CVD method for the preparation of thin oxide films and coatings. [ABSTRACT FROM AUTHOR]

A catalyst system capable of effecting the cross-coupling of ammonia or primary alkylamines with (hetero)aryl sulfamates, carbamates, or pivalates is reported for the first time. The air-stable nickel(II) pre-catalyst C1 tolerates a broad spectrum of heterocyclic functionality within both reaction partners, as well as ether, nitrile, pyrrole, trifluoromethyl, and boronate ester substituents. In the case of reactions involving primary alkylamines and (hetero)aryl sulfamates and carbamates, room-temperature cross-couplings were achieved. [ABSTRACT FROM AUTHOR]

Electronic, steric and leaving group effects for Ni-catalyzed direct arylations using C−O electrophiles were benchmarked. The scope of arylations with pivalates was general with respect to both the electronics on the electrophile and the azoles. Furthermore, the arylation of azoles with tosylates, mesylates and carbamates with varying electronics was explored, and showed electronic trends similar to those of the pivalate reactions. Finally, the relative rate of arylation of 5-methyl benzoxazole with two electronically-similar electrophiles bearing different leaving groups was established. The results from these studies implicate the following order of relative reactivity: mesylates>pivalates>carbamates. [ABSTRACT FROM AUTHOR]

The reaction products of [Cd(piv)] (piv is-OCBu) with isoquinoline (iqn), 2,4-lutidine (lut), phenanthridine (phend), 2,3-cyclododecenopyridine (cpy), and triethylamine (EtN) were synthesized and their structures were determined. The steric factors were found to play a more important role in cadmium( ii) pivalate complexes compared to 3d metal carboxylates in the +2 oxidation state. The reaction of [Cd(piv)] with isoquinoline produces only the mononuclear complex [Cd(piv)(iqn)] ( 1). The reaction of [Cd(piv)] with pyridine derivatives bearing a bulky substituent at the α position is accompanied by the formation of symmetrical dinuclear complexes of the composition [Cd(piv)(L)]. In the complexes with L = lut ( 2) or phend ( 3), the cadmium( ii) atoms are linked by two chelating-bridging carboxylate groups; in the complex with L = cpy ( 4), by four bidentate-bridging groups. The reaction of [Cd(piv)] with EtN in a solution of MeCN gives the centrosymmetric linear trinuclear complex [Cd(piv)(EtN)] ( 6); in a mixture of benzene and hexane, the ionic compound (HEtN)[Cd(piv)(HO)] ( 7). The crystal structures of all synthesized compounds were determined by X-ray diffraction. [ABSTRACT FROM AUTHOR]

The behavior of 4-thienyl substituted pyrimidine ligands (L 1–3 ) has been studied for the series of their reactions with various salts of 3d metals (Co, Zn, Ni, Cu) and platinoids (Pt, Pd). In particular, mononuclear Co(OTf) 2 (L 1–3 ) 2 (H 2 O) 2 (MeCN) 2 ( 1 ), binuclear Co 2 (Piv) 2 (L 1–3 ) 4 ( 2a , b ), Cu 2 (Piv) 2 (L 1–3 ) 2 ( 5a , b ), heterometallic polynuclear Li 2 Co 2 (Piv) 6 (L 1–3 ) 2 ( 4 ) and chelate [(L 1 )Pd(OAc)] 2 ( 6 ) complexes have been obtained. The structures of all complexes have been established by X-ray diffraction. Also magnetic properties of coordination compounds 1 , 2 , 4 and 5 have been studied in details. In particular, mononuclear Co(II) complexes 1 and 4 proved to exhibit paramagnetism with large positive zero-field splitting parameters. Dinuclear Co(II) complexes 2a , b show weak antiferromagnetic interactions. Dinuclear Cu(II) complexes 5a , b demonstrate strong antiferromagnetic superexchange interactions via four carboxylate bridges. The systems 2a , b and 5a , b are isolated as exchange coupled dimers. [ABSTRACT FROM AUTHOR]

When studying the synthesis of NBu[Co(piv)] and NBu[Cu(piv)], where NBu is a tetrabutylammonium cation and piv is a pivalate anion, in some cases we obtained a few crystals of the tetranuclear complexes (NBu)[M(piv)(AcO)(HO)], where M = Co, n = 4; M = Cu, n = 2, AcO is the acetate anion. These complexes contain only deprotonated pivalate and acetate anions as coordinated organic ligands and represent a rare type of polynuclear compounds, which have not been obtained earlier as the major individual phase. For Co, a method was developed for the straightforward synthesis of the complex (NBu)[Co(piv)(AcO)(HO)]. [ABSTRACT FROM AUTHOR]

Using single crystal X-ray diffraction the structure of polynuclear [Ni(OH)(Piv)(HOCHO)(HPiv)], {K[Ni(CO)(Piv)(OH)(HOCHOH)]}HPiv, {[Ni(OH)(Piv)(HOCHO)(MeCO)(HOCHOH)]×(Piv)}, and {K[NiL(Piv)]} complexes, where HOCHOH 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. [ABSTRACT FROM AUTHOR]

Abstract: The reaction system MnII/CeIII/IV/(CH3)3CCO2 − has been investigated and has yielded four Mn x Ce y and one MnIII 4 compounds. Reactions in the presence of NBu n 4MnO4 afforded a MnIII 8CeIV compound [Mn8CeO8(ButCO2)12(DMF)4] (1), consisting of a CeIV atom inside a loop of eight MnIII ions. Reactions also containing 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy) gave [Mn2Ce2O2(OH)2(ButCO2)4(NO3)4(phen)2] (2) or [Mn2Ce2O2(OH)2(ButCO2)4(NO3)4(bpy)2] (3), respectively, containing the MnIII 2CeIV 2O2 core. In contrast, reactions in the presence of 2-(hydroxymethyl)pyridine (hmpH) yielded the MnIII 4CeIII 2 cluster [Mn4Ce2O2(ButCO2)5(NO3)5(hmp)4] (4), with an unprecedented [Mn4Ce2(μ4-O)2] core, and a homometallic, butterfly-like MnIII 4 cluster [Mn4O2(ButCO2)6(pic)2(H2O)2] (5), in which oxidation of hmp− to picolinate (pic−) has occurred. Variable-temperature, dc and ac measurements were performed on polycrystalline samples of 1–5. Fitting of the obtained magnetization (M) versus field (H) and temperature (T) data by matrix diagonalization, and including only axial anisotropy (zero-field splitting, ZFS), gave a ground state spin of S =5 for 1·2DMF. The magnetic susceptibility data for 2·2Et2O and 3 up to 300K were fit and revealed very weak ferromagnetic interactions between the MnIII ions; J = +0.5(2)cm−1 for 2·2Et2O, and J = +0.3(1)cm−1 for 3. Complexes 4·3MeCN and 5·2ButCO2H have S =0 ground states. [Copyright &y& Elsevier]

To find the factors favorable for the appearance of chemomechanical activity of heterospin crystals, a series of new heterospin complexes were synthesized and characterized. It includes [Cu(tfac)L]·2CHCl, [Cu(tfac)L]·2EtOH, [[Cu(pfu)]L]·1/2CHCl, [Cu(pfh)L]·1/2CHCl, [Cu(piv)L]·2MeOH, [Co(piv)L], [ $$ Cu(hfac)_2 L^{CD_3 } _2 $$], [Cu(hfac)L]·CHCl, and [Cu(hfac)L] (L, $$ L^{CD_3 } $$, and L are N-methylimidazolyl-, N-trideuteriomethylimidazolyl-, and N-methyltriazolyl-substituted nitronyl nitroxides, respectively; tfac, hfac, pfu, pfh, and piv are the charged coordinated diamagnetic ligands 1,1,5,5-tetrafluoropentane-2,4-dionate, 1,1,1,5,5,5-hexafluoropentane-2,4-dionate, 1,1,1,2,2,3,3,4,4,8,8,9,9,10,10,11,11,11-octadecafluoroundecane-5,7-dionate, 1,1,1,5,5,6,6,6-octafluorohexane-2,4-dionate, and 2,2-dimethylpropionate, respectively). The crystal and molecular structures of all compounds were determined. The results of the X-ray diffraction study of the complex [Ni(hfac)L] synthesized earlier are reported. In the solid state of the complexes [Cu(pfh)L] and [Co(piv)L], the paramagnetic ligands are cis-coordinated to the central atom in a monodentate fashion via the donor N atom of the imidazole ring. In the dinuclear complexes [[Cu(pfu)]L] and [Cu(hfac)L], the paramagnetic ligands are also in cis positions but act as bridges through coordination of the donor N atoms of the azole ring and the O atom of the nitronyl nitroxide moiety to different Cu ions. In the solid complexes $$ Cu(hfac)_2 L^{CD_3 } _2 $$ , [Cu(hfac)L], [Cu(tfac)L]·2CHCl, [Cu(tfac)L]·2EtOH, and [Cu(piv)L]·2MeOH, the nitronyl nitroxide radicals in the mononuclear heterospin molecules are in trans positions. The packing motif in the crystal structures of the complexes $$ Cu(hfac)_2 L^{CD_3 } _2 $$ , [Cu(tfac)L]·2CHCl, and [Cu(tfac)L]·2EtOH is the same as that in the previously studied complexes [M(hfac)L] exhibiting chemomechanical activity. Among the complexes under consideration, only crystals of $$ Cu(hfac)_2 L^{CD_3 } _2 $$ can exhibit chemomechanical activity, that is to make jumps upon heating or irradiation. The results of the present study suggest that the packing of the solid-state structure plays a key role in the generation of mechanical activity of the crystals. [ABSTRACT FROM AUTHOR]

The reaction of cobalt(II) bis(hexafluoroacetylacetonate) (Co(hfac)) with polynuclear Co or Co pivalates, [NaCo(OH)(Piv)(EtOH)], [Co(HO)(Piv)(HPiv)], and [CoCo(O)(Piv)(HO)(THF)]·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 [NaCo(hfac)(Piv)(MeCO)], the tetranuclear complex [Co(Piv)(hfac)(OH)(HPiv)]·HPiv, and the tetradecanuclear complex [CoCo(Piv)(hfac)(OH)(O)(HPiv)]·2HPiv·2HO·3CH, respectively. The tetradecanuclear complex has an unusual ability to precipitate nitroxides from solution, due to which the following new heterospin crystalline solids were synthesized: [Co(Piv)(hfac)(OH)(O)(HO)(HPiv)]·2NIT-Me·2HPiv·CH, [Co(Piv)(hfac)(OH)(O)(HPiv)]·2NIT-Et·2CHCl, [Co(Piv)(hfac)(OH)(O)(HPiv)]·2NIT-Ph·2CH, [Co(Piv)(hfac)(OH)(O)(HPiv)]·2L·2CHCl, and [Co(Piv)(hfac)(OH)(O)(HPiv)]·2L·CH, where NIT-Me, NIT-Et, and NIT-Ph are 2-imidazoline nitroxides, L is 3-imidazoline nitroxide, and L 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 μ-OH groups in the [Co(Piv)(hfac)(OH)(O)(HPiv)] 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 [Co(Piv)(hfac)(OH)(O)(HO)(NIT-H)]·4HPiv·2HO. [ABSTRACT FROM AUTHOR]

The heterospin mixed-ligand complex [Ni(OH)Piv(hfac)(NIT-Ph)] ( 1) (NIT-Ph is 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1 H-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 [Ni(OH)Piv(hfac)(MeCO)] 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 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. 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 [NiPiv(hfac)(OH)(MeCO)] with the nitronyl nitroxide radicals 4,4,5,5-tetramethyl-2-(4-pyridyl)-4,5-dihydro-1 H-imidazol-1-oxyl 3-oxide (NIT- p-Py) or 4,4,5,5-tetramethyl-2-(1-methyl-1 H-imidazol-5-yl)-4,5-dihydro-1 H-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)(NIT- p-Py) and Ni(hfac)(NIT-Iz), respectively. The reaction of 4,4,5,5-tetramethyl-2-(1-methyl-1 H-imidazol-5-yl)-4,5-dihyd-ro-1 H-imidazol-1-oxyl (Im-Iz), which is the imine analog of NIT-Iz, with [NiPiv(hfac)(OH)(MeCO)] afforded the decanuclear complex [Ni(OH)Piv(hfac)(Im-Iz)(HO)]. 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. [ABSTRACT FROM AUTHOR]