Russian Journal of Coordination Chemistry最新文献

The reaction of triphenylcyclopentadienyl potassium and bipyridine with lanthanum, praseodymium, erbium, lutetium, and scandium chloride tetrahydrofuranates results in the formation of binuclear [Cp^Ph3Ln(Bipy)Cl(μ₂-Cl)]₂ (Ln = La (I), Pr (II)) and mononuclear [Cp^Ph3Ln(Bipy)Cl₂(THF)] (Ln = Er (III), Lu (IV), [Cp^Ph3Sc(Bipy)Cl₂] (V) complexes (Cp^Ph3 = 1,2,4-triphenylcyclopentadienyl, Bipy = bipyridine). The decrease in the REE radius in the series La…Sc results in the formation of mononuclear instead of binuclear complexes and in a decrease in the coordination number of the central ion. The coplanar arrangement of two different π-systems gives rise to stacking interactions between the triphenylcyclopentadienyl ligand and bipyridine. The molecular structure of complexes I–V was established by X-ray diffraction analysis (CCDC nos. 2308609 (I), 2308608 (II), 2308610 (III), 2308611 (IV), 2308607 (V)).

The dehydrogenation of dimethylamine-borane (DMAB) catalyzed by the iminophosphonamide rhodium(III) complexes [Cp*RhCl{Ph₂P(N–p-Tol)(NR)}] (Iа, R = p-Tol; Ib, R = Me) as well as their in situ formed fulvene [(η⁴-C₅Me₄CH₂)Rh(NPN)] (IIa, IIb) and diene [(η⁴-C₅Me₅H)Rh(NPN)] (IIIa, IIIb) rhodium(I) derivatives is studied. Catalysts IIIa and IIIb turn out to be the most active and demonstrate a TOF activity of 110 (IIIа) and 540 h^–1 (IIIb) at 40°С in toluene. The activity decreases significantly in more polar and coordinating THF. At the same time, the rate of DMAB dehydrogenation by complexes Iа and Ib is lower by 10–30 times, and fulvene complexes Iа and Ib are rapidly deactivated after the active initial period (<20% conversion). The kinetic studies show that the reaction has the first order with respect to the substrate and the catalyst. The model ¹¹В NMR experiments confirm that the reaction proceeds via the intermediate formation of a monomer Me₂N=BH₂, which rapidly dimerizes to (Me₂N–BH₂)₂. The mechanism of DMAB dehydrogenation with the formation of unstable hydride intermediate [Cp*RhH{Ph₂P(N–p-Tol)(NR)}] (IVa, IVb) is proposed on the basis of the preliminarily ³¹Р NMR results and published data.

New coordination polymers were synthesized. A ditopic centrosymmetric organic ligand containing oxazole heterocycles, 4,8-dichlorobenzo[1,2d:4,5d']bis(oxazole)-2,6(3H,7H)-dithione (H₂L), was prepared and structurally characterized. It was shown that deprotonated H₂L forms non-luminescent binuclear molecular complexes Li₂L(THF)₆ (I) and Na₂L(DME)₄ (II) with alkali metals, while complexes of H₂L with lanthanides are ionic compounds [Ln(DMSO)₈][L]_1.5 (Ln = Nd (III), Yb (IV)) exhibiting moderate metal-centered emission in the near-infrared (IR) range, despite the absence of coordination of the ligand L to lanthanide ions. The molecular structures of H₂L·2DMSO and I–III were established by X-ray diffraction (CCDC nos. 2320461 (H₂L·2DMSO), 2320462 (I), 2320463 (II), 2320464 (III)).

The reaction of [(Dpp-bian)DyI(Dme)₂] (Dpp-bian is 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene, Dme is CH₃OCH₂CH₂OCH₃) with Cp*K (Cp* is C₅Me₅) in toluene followed by crystallization from benzene affords crystals of the 1D coordination polymer [(Dpp-bian)DyIKCp*]_n (I)·2.6C₆H₆ (26%) and crystals of the monomeric complex [(Dpp-bian)DyCp*(Dme)] (II)·1.5C₆H₆ (12%). The same reaction in 1,2-dimethoxyethane followed by crystallization from benzene makes it possible to isolate only complex II·1.5C₆H₆ in a yield of 48%. The synthesized compounds are characterized by IR and UV spectroscopy and elemental and thermogravimetric analyses. Their molecular structures are determined by XRD (CIF files CCDC nos. 2298407 (I) and 2298408 (II)).

New samarium complex of 5-phenyl-2,2'-bipyridine with the diethylenetriaminotetraacetic acid (DTTA) residue in the C6 position, [(L₂)Sm₂Na₅(H₂О)₉(C₂O₄)]_n (I), is synthesized. The structure of complex I is studied by XRD (CIF file CCDC no. 2217968). The complex in the crystal is found to be a one-dimensional coordination polymer, and the 2,2'-bipyridine fragments do not chelate the Sm³⁺ cation. The complex is characterized by a luminescence response to the addition of an excess of zinc cations.

Ruthenium α-diimine complexes are widely known for their unique low-lying excited states and potent light absorption capabilities in the visible and NIR regions. A few specially constructed Ru α-diimine complexes have also shown enormous potential in the biomedical field. Several Ru-diimine complexes are well known for their catalytic activity. In this context, the simplest α-diimine system is 1,4-diaza-1,3-butadiene, abbreviated as (DAB/DAD), which received the greatest attention from the research communities. DAB ligands are redox-active. DAB ligands typically function as effective electron donors by employing lone pairs of nitrogen atoms and the π-electrons of the C=N bonds while coordinating the metal ion. The structural, electronic, and photophysical properties of the metal-mediated (DAB) complexes largely depend on the substitution of the ligand backbone as well as metal precursors. A versatile ‘redox noninnocent’ 1,4-diaza-1,3-butadiene motif can stabilise different oxidation states of ruthenium metal depending on the reaction conditions and the presence of co-ligands. The comparative studies of the structural and electrical characteristics of diverse ruthenium-DAB compounds are intriguing, which opens up a new route for researchers to utilise them in a variety of application domains. It is challenging and fascinating to determine the precise electronic structure of redox noninnocent diimine complexes in the presence of a ‘redox active’ metal like ruthenium. In this concise review, we provided a brief overview of the structural and electrical features of various Ru DAB complexes that solely comprise (–N=CH–CH=N–) fragments in the skeleton.

Using the synthesized salt Gd(NCS)₃·6H₂O, previously unknown mononuclear molecular complexes [Gd(H₂O)(bpy)₂(NCS)₃]·0.5(bpy)·H₂O, [Gd(H₂O)(phen)₂(NCS)₃]·phen·0.5H₂O as well as ionic ones [Hbpy][Gd(NCS)₄(bpy)₂]·H₂O, [Hphen][Gd(NCS)₄(phen)₂] (bpy is 2,2'-bipyridine, phen is 1,10-phenanthroline) were prepared. Structural characteristics of the obtained compounds were determined using X-ray diffraction data. The magnetic susceptibility and EPR data of the new Gd complexes are considered taking into account the features of their composition and structure. Due to the peculiarities of the electronic structure, Gd complexes can serve as test systems for analyzing the field strength of ligands and the geometry of the local environment of the 4f-metal ion. It is shown that EPR spectroscopy is highly efficient method for determining the spin Hamiltonian parameters and, consequently, for characterizing the local environment of the gadolinium ion in complexes. However, the EPR method does not allow one to determine the sign of the splitting parameter in the zero field D, which requires additional studies.

The reactions of cobalt(II) nitrate or perchlorate with acetamide (AA) or carbamide (Ur) in an aqueous medium results in formation of coordination compounds [Co(Ur)₄](NO₃)₂ (I), [Co(Ur)₆](NO₃)₂ (II), [Co(AA)₄(H₂O)₂](NO₃)₂ (III), [Co(AA)₄(H₂O)₂](NO₃)₂∙2AA (IV), [Co(Ur)₆](ClO₄)₂, (V), [Co(AA)₄(H₂O)₂](ClO₄)₂ (VI), and [Co(AA)₆](ClO₄)₂ (VII). The compositions of the isolated complexes are determined by physicochemical methods, and the crystal and molecular structures of compounds II, V, VI, and VII are solved. Specific features of the thermal behavior of all synthesized compounds in a wide temperature range are studied in detail. These compounds are shown to be used as precursors in the preparation of nanosized Co₃O₄ using self-propagating high-temperature synthesis. The catalytic activity of thus synthesized Co₃O₄ in the model epoxidation of allyl alcohol is studied.

Three mono(arylhydrazino)acenaphthenones, that is, mono(2-pyridylhydrazino)acenaphthenone (Py-mhan, L¹), mono(4-cyanophenylhydrazino)acenaphthenone (4-CN-Ph-mhan, L²), and mono(3,4,6-trifluoro-2-pyridylhydrazino)acenaphthenone (^FPy-mhan, L³), were synthesized by the reaction of acenaphthene quinone with the appropriate arylhydrazine salt; compounds L² and L³ were obtained for the first time. The subsequent reaction of L¹ with nickel chloride in 2 : 1 ratio led to the octahedral complex [Ni(Py-mhan)₂] (I), in which Py-mhan acts as a tridentate ligand. All of the prepared compounds were characterized by elemental analysis, IR and ¹H NMR spectroscopy, and cyclic voltammetry; the crystal structures of L³ and I were determined by X-ray diffraction.

Five coordination compounds of the general formula [LnL₂(NO₃)₃]_n (Ln³⁺ = Eu (I), Sm (II), Tb (III), Dy (IV), and Gd (V)) based on 2-[((4-chlorophenyl)amino)methylene]-5,5-dimethylcyclohexane-1,3-dione (L) are synthesized. The crystal structures of the ligand and complex III are determined by X-ray diffraction (XRD) analysis of single crystals (CIF files CCDC no. 2298715 (L) and 2298716 (III)). Complex III is polymeric due to the bidentate-bridging coordination of the ligand by the oxygen atoms of the cyclohexanedione fragment, and the coordination number of the central atom is ten. According to the powder XRD data, all synthesized polycrystalline compounds are isostructural to the single crystals of complex III. The photoluminescence properties of the ligand and coordination compounds in the polycrystalline state are studied. The energy transfer from the ligand to lanthanide(III) ion is shown to proceed via the “antenna” mechanism in the case of the europium(III), samarium(III), and terbium(III) compounds. Among the series of the complexes, the highest quantum yield is observed for compound I (21.9%), and the sensitization efficiency of the europium(III) complex is 43.5%.