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1.
The structures of new compounds containing Zn(II) ions and bpp (1,3-bis(4-pyridyl)propane) ligands have been determined. The coordinating halides (Br or Cl) produce one-dimensional compounds 6 and 7, and intra- and inter-chain CH?X (X = Br or I) interactions play roles for building crystal structures with the flexible bpp ligands. The non-coordinating anions do not produce hydroxyl bridged zinc cations or polymeric compounds, and produce only a monomeric complex 4 containing four bpp ligands and two water ligands. Previously reported polymeric compounds 1 and 2 containing hydroxyl-bridged zinc cations [Zn2OH] were found to carry out the catalytic transesterification of a range of esters with methanol at room temperature under the mild conditions, whereas the rest of compounds did not catalyze the transesterification reactions at all. In addition, the catalysts 1 and 2 have shown even better catalytic activity than zinc salts Zn(NO3)2 and Zn(OTf)2.  相似文献   

2.
Some cobalt carboxylate (both mononuclear as well as binuclear) complexes have been prepared by using hindered hydrotris(3,5-diisopropyl-1-pyrazolyl)borate (TpiPr2) as supporting ligand. The reaction of [TpiPr2Co(NO3)] (2) with sodium benzoate resulted in the formation of acetonitrile coordinated complex [TpiPr2Co(OBz)(CH3CN)] (3) whereas the reaction of 2 with sodium fluorobenzoate gave coordinately unsaturated five coordinate complex of the type [TpiPr2Co(F-OBz)] (4). The oxidation of compound 4 in the presence of 3,5-diisopropylpyrazole resulted in the formation of a unique compound (5) where only one methine carbon of isopropyl group on pyrazole ring of hydrotris(3,5-diisopropyl-1-pyrazolyl)borate oxidized and coordinated with cobalt center. In compound 5, the binding behavior of fluorobenzoate also changes from bidentate to monodentate and the nonbonded oxygen atom formed intramolecular hydrogen bond with the hydrogen atom of the NH fragment of the coordinated . X-ray crystallography and IR studies confirmed the existence of hydrogen bonding in complex 5. The pyrazolato bridged binuclear cobalt(II) complex (6) was prepared by the reaction of hydrated cobalt(II) nitrate, 3,5-diisopropylpyrazole and sodium nitrobenzoate where, each cobalt is four coordinate. The X-ray structure of 6 showed that the NH fragment of terminally coordinated formed intramolecular hydrogen bonding with nonbonded oxygen atom of monodentately coordinated nitrobenzoate.  相似文献   

3.
The preparation, crystal structure and variable temperature-magnetic investigation of three 2-(2′-pyridyl)imidazole-containing chromium(III) complexes of formula PPh4[Cr(pyim)(C2O4)2]·H2O (1), AsPh4[Cr(pyim)(C2O4)2]·H2O (2) and [Cr2(pyim)2(C2O4)2(OH2)2]·2pyim · 6H2O (3) [pyim = 2-(2′-pyridyl)imidazole, , and ] are reported herein. The isomorphous compounds are made up of discrete [Cr(pyim)(C2O4)2] anions, cations [X = P (1) and As (2)] and uncoordinated water molecules. The chromium environment in 1 and 2 is distorted octahedral with Cr-N and Cr-O bond distances varying in the ranges 2.040(3)-2.101(3) and 1.941(3)-1.959(3) Å, respectively. The angle subtended by the chromium(III) ion by the two didentate oxalate ligands cover the range 82.49(12)-82.95(12)°, values which are somewhat greater than those concerning the chelating pyim molecule [77.94(13) (1) and 78.50(13)° (2)]. Complex 3 contains discrete centrosymmetric [Cr2(pyim)2(C2O4)2(OH)2] neutral units where the two chromium(III) ions are joined by a di-μ-hydroxo bridge, the oxalate and pyim groups acting as peripheral didentate ligands. Uncoordinated water and pyim molecules are also present in 3 and they contribute to the stabilization of its structure by extensive hydrogen bonding and π-π type interactions. The values of the intramolecular chromium-chromium separation and angle at the hydroxo bridge in 3 are 2.9908(12) Å and 99.60(16)°, respectively. Magnetic susceptibility measurements of 1-3 in the temperature range 1.9-300 K show the occurrence of weak inter- (1 and 2) and intramolecular (3) antiferromagnetic couplings. The magnetic properties of 3 have been interpreted in terms of a temperature-dependent exchange integral, small changes of the angle at the hydroxo bridge upon cooling being most likely responsible for this peculiar magnetic behavior.  相似文献   

4.
Four new coordination networks based on dipyridyl linkages 2,6-(N,N′-di(4-pyridyl)amino)pyridine (dpap) or 1,3-bis(4-pyridyl)propane (bpp) and different dicarboxylates have been synthesized and structurally characterized. Using dpap to react with two different dicarboxylates, maleic acid (H2mal) and 4,4′-sulfonyldibenzoate (H2sdba), respectively, two different two-dimensional (2D) coordination polymers of Cd(II), [Cd(dpap)(mal)]n (1) and {[Cd(dpap)(sdba)] · 2H2O}n (2) were obtained. Compound 1 features a 42-membered bimetallic macrocyclic structural motif which is extended by mal groups to form a 2D network. In the case of 2, two different layers can be achieved depending on the conformation of sdba. The layer has a (8210) net topology with Cd as nodes and dpap, sdba bridges as the connectors. The overall structure of {[Mn(dpap)(sdba)] · 1.5H2O}n (3) similar to that of 2 despite the presence of different metal ions. When dpap was replaced by bpp to react with Co(NO3)2 · 6H2O, another 1D coordination polymer, {[Co(bpp)(H2O)4] · sdba}n(4) was constructed. The 1D chains join sdba to make an overall 3D supramolecular architecture by hydrogen-bonding interactions ( (22), (12)). The Cd coordination polymers exhibit strong solid-state luminescence emission at room temperature. Thermal stability of these crystalline materials has been explored by thermogravimetric analysis of mass loss.  相似文献   

5.
The preparation and magnetic properties of three copper(II) compounds of formulae [Cu2(bpcam)2(H2O)2(C2O4)] (1), [Cu2(bpcam)2(H2O)4(C4O4)] · 10 H2O (2) and Cu2(bpcam)2(C5O5)(H2O)3 (3) [bpcam = bis(2-pyrimidyl)amidate, and are reported. The structures of two of them (1 and 2) have been solved by single crystal X-ray diffraction and consists of centrosymmetric discrete copper(II) dinuclear units bridged by bis-bidentate oxalate (1) and bis-monodentate squarate (2), with the bpcam group acting as a terminal tridentate ligand. Each copper atom in 1 exhibits a distorted elongated octahedral coordination geometry. Three bpcam nitrogen atoms and one oxalate oxygen define the basal plane while the other oxalate oxygen and a water molecule take up the axial positions. Each copper atom in 2 is in an elongated octahedral surrounding with three bpcam nitrogen atoms and one squarate oxygen in the equatorial plane and two water molecules in the axial positions. The intramolecular copper-copper separations are 5.677(1) (1) and 7.819(53) Å (2). Magnetic susceptibility measurements for 1-3 in the temperature range 1.9-290 K show the occurrence of weak ferromagnetic interactions through oxalato (J = +0.75 cm−1) and squarato (J = +1.26 cm−1), the Hamiltonian being defined by . These values are analyzed and discussed in the light of the available magneto-structural data for analogous systems. The quasi-Curie law observed in 3 (θ = −1.15 K) contrasts with the significant antiferromagnetic interaction through bis-chelating croconate in other structurally characterized croconate-bridged copper(II) complexes and rules out the presence of bridging croconate in this compound.  相似文献   

6.
The preparation, crystal structures and magnetic properties of three copper(II) compounds of formulae [Cu2(dmphen)2(dca)4] (1), [Cu(dmphen)(dca)(NO3)]n (2) and [Cu(4,4-dmbpy)(H2O)(dca)2] (3) (dmphen=2,9-dimethyl-1,10-phenanthroline, dca=dicyanamide and 4,4-dmbpy=4,4-dimethyl-2,2-bipyridine) are reported. The structure of 1 consists of discrete copper(II) dinuclear units with double end-to-end dca bridges whereas that of 2 is made up of neutral uniform copper(II) chains with a single symmetrical end-to-end dca bridge. Each copper atom in 1 and 2 is in a distorted square pyramidal environment: two (1) or one (2) nitrile-nitrogen atoms from bridging dca groups, one of the nitrogen atoms of the dmphen molecule (1 and 2) and either one nitrile-nitrogen from a terminal dca ligand (1) or a nitrate-oxygen atom (2) build the equatorial plane whereas the second nitrogen atom of the heterocyclic dmphen fills the axial position (1 and 2). The copper-copper separations through double (1) and single (2) end-to-end dca bridges are 7.1337(7) (1) and 7.6617(7) (2). Compound 3 is a mononuclear copper(II) complex whose structure contains two neutral and crystallographically independent [Cu(4,4-dmbpy)(H2O)(dca)2] molecules which are packed in two different layer arrangements running parallel to the bc-plane and alternating along the a-axis. The copper atoms in both molecules have slightly distorted square pyramidal surroundings with the two nitrogen atoms of the 4,4-dmbpy ligand and two dca nitrile-nitrogen atoms in the basal plane and a water oxygen in the apical position. A semi co-ordinated dca nitrile-nitrogen from a neighbour unit [2.952(6) Å for Cu(2)-N] is in trans position to the apical water molecule in one of the two molecules, this feature representing part of the difference in supramolecular connections in the alternating layers referred to above. Magnetic susceptibility measurements for 1-3 in the temperature range 1.9-290 K reveal the occurrence of weak antiferromagnetic interactions through double [J=−3.3 cm−1 (1), ] and single [J=−0.57 cm−1 (2), ] dca bridges and across intermolecular contacts [θ=−0.07 K (3)].  相似文献   

7.
Versatile synthetic routes have been applied to prepare the new asymmetric phosphine-phosphite ligands 8 and 12. The chiral ligands have been designed so that the corresponding ligating groups have similar electronic properties and steric bulk, but 8 forms 6-, while 12 forms 7-membered chelate rings in their coordination compounds. The chelate size variation results in a markedly different coordination behavior towards Pt(II). In their reactions with Pt(PhCN)2Cl2 at 1:1 stoichiometry 12 forms the expected Pt(12)Cl2 complex, while 8 gives the cation quantitatively. In the kinetically controlled reaction is the major product even at a 8:Pt(PhCN)2Cl2 = 1:2 ratio. Most interestingly, at 1:1 ligand to precursor ratio, cation rearranges to Pt(8)Cl2 within one day, indicating that the neutral complex is thermodynamically more favorable.  相似文献   

8.
Reaction of [Tp′W(CO)2(PhCCPh)][OTf] (1b) (Tp′ = hydridotris(3,5-dimethylpyrazolyl)borate) with excess aziridine or 2-methylaziridine followed by protonation with produces chiral tungsten(II) amine complexes (3, 4; R = Me, Ph). An azetidine amido complex, Tp′W(CO)(PhCCMe)(H2) (5) is synthesized by reaction of [Tp′W(CO)2(PhCCMe)][OTf] (1a) with excess azetidine. Oxidation of amido complex 5 with I2 in the presence of a weak base provides the corresponding 1-azetine complex, (6). Addition of methylmagnesium bromide to complex 6 results in formation of predominantly one diastereomer (SWRC/RWSC) (96:4 dr) of the 2-methylazetidine complex, Tp′W(CO)(PhCCMe)(H2) (7). Reaction of complex 5 with results in formation of a cationic azetidine complex, (8). Reaction of 1b with excess piperidine followed by oxidation affords 2,3,4,5-tetrahydropyridine complex 9b, . Formation of an enamido complex, Tp′W(CO)(PhCCPh)(H2) (10), is observed upon addition of base to 9b. Subsequent addition of [D+] to the enamido β-carbon results in the formation of the deuterated product, 9b-d1, as determined by 2H NMR. Seven X-ray crystal structures have been determined, and these encompass complexes with 3, 4, and 6-membered heterocyclic ligands. Crystal structures are reported for two aziridine adducts (2, 4) two neutral amido complexes (5, 7), one cationic imine complex (6), and one cationic amine (8) complex derived from azetidine, and the imine complex formed from piperidine (9).  相似文献   

9.
Treatment of TeCl4 with either K[{N(C6H3Pri2-2,6)C(H)}2CPh] [≡K(L)] (1) in thf/Et2O or [H2(L)]Cl (2) in Et2O furnished [Cl4Cl?HH?OEt2]·0.5(Et2O) (3), whilst 2TeCl4 with a mixture of single equivalent portions of 2,6-Pri2C6H3NH2 and H(L) produced [Cl4] (4). The X-ray structures of each of crystalline 3 and 4 show that the Te atom is at the centre of an only slightly distorted square pyramid, with a Cl atom of 3 or a C of 4 in the axial position. The N1 and N2 atoms of the π-delocalised β-dialdiminium moiety of 3 have H-bond contacts, involving short N1-H?OEt2 and N2-H?Cl5 distances. The two longer of the four Te-Cl bonds of 4 are close to the N atom of the neighbouring molecule; whilst two of the H atoms of each H3 fragment are H-bonded to the O atoms of the two thf ligands, the third being close to two Cl atoms of an adjacent molecule, thus forming H-bonded chains of molecules.  相似文献   

10.
Three novel heterometallic complexes [Cu(en)2Cr(NCS)4(NH3)2][Cr(NCS)4(NH3)2] · 6dmf (1), [Cu(en)2Cr(NCS)4(NH3)2](OAc) (2) and [{Cu(en)2}3{Cr(NCS)4(NH3)2}2(NCS)2](NCS)2 (3) have been synthesized in a one-pot reaction from copper powder, Reineckes salt, NH4X [X = OAc (2), NCS (3)] in a dmf (1) or CH3CN (2, 3) solution of ethylenediamine (en). X-ray studies showed that 1 and 2 consist of cationic polymeric chains, formed by and building blocks that bridged through thiocyanate anions. In both complexes, distinct hydrogen bonds are present and serve to increase the dimensionality of the compound from one to two (in 1) or three (in 2). The main structural feature of 3 is the pentanuclear Cu3Cr2 cation which is H-bonded with uncoordinated thiocyanate groups generating a 3D supramolecular assembly. The shortest Cu?Cr distances are 5.840(1) Å for 1, 5.856(1) and 6.018(3) Å for 2 and 6.009(9) and 6.465(9) Å for 3. Compounds 1 and 2 are essentially paramagnets whereas compound 3 shows a weak antiferromagnetic coupling. The magnetic properties are simulated and discussed in terms of the structural features.  相似文献   

11.
The reaction of 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)benzene (bib) ligand with silver(I) nitrate in a 1:1 molar ratio generated a [2 + 2] metallocyclic complex [Ag2(bib)2](NO3)2 · 2H2O, in which bib ligand displayed in cis configuration. When the additional competing ligands/counterions, such as oxlate salt, 1,2-diaminoethene (en), 1,3-diaminopropane (pn), and were introduced, respectively, to the above-mentioned reaction solution, ring-open polymerization of sliver(I) complexes {[Ag(bib)]NO3 · H2O}n (1), {[Ag(bib)2]X}n ( (2), (3)), {[Ag2(bib)2(NO2)](NO2) · 19/8H2O}n (4) and {[Ag2(bib)2](V4O12)0.5 · 3H2O · 2MeCN}n (5) were generated. In compounds 1, 4 and 5, bib ligand adopts trans configuration and twists around the Ag-Ag axis, giving rise to single-stranded helical structure with short adjacent Ag?Ag distances of 3.56, 3.56, 3.50 and 3.63 Å, respectively. Compounds 2 and 3 are 1D coordination polymers fusing the [2 + 2] metallocycle [Ag2(bib)2]2+, in which bib ligand exhibits in cis configuration and the metallocycles have longer Ag?Ag distances of 8.52 Å in 2 and 8.61 Å in 3 along with the strong intracyclicπ-π interactions between phenyl groups. Cis and trans configurations of bib coexist in solution and crystallize in complexes 1 and 2 in the solid state in the presence of en or pn. The solution of 1 and 2 can be converted into 3 via the addition of the bulky counter anion or into 4 through introduction of the competing ligand/conuterion .  相似文献   

12.
The chloro complexes [PtCl2(RSR′)2] (1-10) (RSR′ = MeSCH2C(O)OMe, 1; MeSCH2C(O)OEt, 2; MeSCH2C(O)Omenthyl(−), 3; MeSCH2CH2C(O)OMe, 4; , 5; EtSCH2C(O)Me, 6; MeSCH(Me)C(O)Me, 7; MeSPh, 8; MeS-o-C6H4Me, 9; and MeS-o-C6H4Et, 10) are obtained in high yield (63-90%) by reaction of [PtCl2(PhCN)2] with the proper thioether in 1/2 molar ratio, in anhydrous chloroform, at reflux under argon for ca. 10 h. The X-ray crystal structure of [PtCl2(MeS-o-C6H4Me)2] (9) shows an almost regular trans square planar geometry (triclinic, space group , a 6.806(1), b 7.789(2), c 10.085(3) Å, α 101.80(2)°, β 69.55(2)°, γ 115.27(2)°, R(Fo) 0.023, ). The dichloro complexes react with silver acetate in a complex manner, which depends on the nature of the thioether, and only with RSR′ = MeSPh the simple diacetato complex [Pt(OAc)2(RSR′)2] is obtained as the major product.  相似文献   

13.
Using an anionic precursor [(Tp)FeIII(CN)3] (1) as a building block, two cyano-bridged centrosymmetric heterotrinuclear complexes, (2) and (3) (en = ethylenediamine), have been synthesized and structurally characterized. In each complex, [TpFe(CN)3] acts as a monodentate ligand toward a central [Mn(C2H5OH)4]2+ or [Ni(en)2]2+ core through one of its three cyanide groups, the other two cyanides remaining terminal. The intramolecular Fe-Mn and Fe-Ni distances are 5.2354(4) and 5.0669(11) Å, respectively. The magnetic properties of complexes 2 and 3 have been investigated in the temperature range of 2.0-300 K. A weak antiferromagnetic interaction between the Mn(II) and Fe(III) ions has been found in complex 2. The magnetic data of 2 can be fitted with the isotropic Hamiltonian: where J and J′ are the intramolecular exchange coupling parameters between adjacent and peripheral spin carriers, respectively. This leads to values of J = −1.37 cm−1 and g = 2.05. The same fitting method is applied to complex 3 to give values of J = 1.2 cm−1 and g = 2.25, showing that there is a ferromagnetic interaction between the Fe(III) and Ni(II) ions.  相似文献   

14.
Six novel metal-organic complex assemblies constructed from a conformation-flexible ligand - pyridine-4-acetamide (PAT) and inorganic CuII and CoII salts have been synthesized and structurally characterized by single crystal X-ray diffraction analysis. Crystal structure analysis reveals five types of architectures by variation of metal salts. In {[Cu(PAT)2Cl2]}n (1) and {[Co(PAT)2Cl2]}n (3), PAT ligands bridge metal centers to form one-dimensional chains. The chains are extended to three dimensions with the aid of two types of hydrogen bonded motifs () and (12)). {[Cu(PAT)2(NO3)](NO3)(THF)}n (5) which exhibits two-dimensional coordinating layers forms open channels filled with solvent molecules. In [Cu(PAT)2Cl2] (2), [Co(PAT)2Cl2] (4) and [Co(PAT)4(H2O)2](NO3)2(THF)2 (6), PAT is observed as a monofunctional ligand. Complex 2 forms one-dimensional hydrogen bonded chains. Crystal structure of complex 4 has a two-dimensional infinite hydrogen-bonded network with and motifs formed by complementary amide-amide hydrogen bonds. [Co(PAT)4(H2O)2](NO3)2(THF)2 (6) crystallizes in centrosymmetric I41/a space group. Complex 6 forms chiral channels which are filled with twisted solvent helices and anion helices. Within each channel the solvent helix and the anion helix have the same handedness; and adjacent channels have opposite handedness. Complexes 1, 2 and complexes 3, 4 illustrate examples of conformational supramolecular isomerism in {[Cu(PAT)2Cl2]} and {[Co(PAT)2Cl2]}, respectively. In these complexes, changes of PAT conformations and coordination geometry of metal center induced the structural versatility.  相似文献   

15.
Reaction of [MoO2(acac)2] with (S is a thioether, S′ a thiophenolate function) yielded the compound Li7(thf)17{MoO}8 · 10thf · hexane, where {MoO}8 represents one 1, three (2, linked, via the oxo group, to [Li(thf)3]+) and two (3a, linked by two [Li(thf)2]+).A mixed-valent variant of 3, (3b, with an additional[Li(thf)3]+ attached to S′), was also identified. The compounds model features pertinent to oxo-transferases containing the molybdopterin cofactor.  相似文献   

16.
In situ reaction of the aminobenzoic acids 2-aminobenzoic acid and 3,5-diaminobenzoic acid with salicylaldehyde provide easy access to the ligands 2-[{(2-hydroxyphenyl)methylene}amino]benzoic acid (L1) and 3,5-bis[{(2-hydroxyphenyl)methylene}amino]benzoic acid (L2). Addition of a Fe(II) or Cu(II) salt to the solution of the ligand yields the corresponding Fe and Cu complexes. The species synthesized have been structurally characterized by single-crystal X-ray diffraction. The Fe(II) complex [Fe(L1)(MeOH)3] (1) crystallizes in the triclinic space group . The Cu(II) complex [Cu(L1)] (2) is a one-dimensional chain and crystallizes in the monoclinic space group P21. The Cu(II) complex [Et3NH]2[Cu2(L2)2] (3) crystallizes in the monoclinic space group P21/n. The magnetic properties of 1, 2 and 3 have been studied, showing that the Cu(II) ions of 2 and 3 are ferromagnetically coupled. Complexes 1 and 3 have strong potential as metal-bearing building blocks for the synthesis of metal-organic frameworks.  相似文献   

17.
Two new cobalt(II) complexes of symmetric hexadentate mixed-ligand N,O [1,12-bis(2-pyridyl)-5,8-dioxa-2,11-diazadodecane (pydado)] and N,S [1,12-bis(2-pyridyl)-5,8-dithia-2,11-diazadodecane (pydadt)] donor atoms have been synthesized as perchlorate salts. The crystal structures show that [Co(pydado)](ClO4)2 · H2O (1) crystallizes in the triclinic space group and [Co(pydadt)](ClO4)2 (2) crystallizes in the monoclinic space group P21/c. The cation [Co(pydado)]2+ is pseudo-octahedral with the two pyridyl groups in trans position. However, in [Co(pydadt)]2+ complex, the size of thioether sulfur atoms imposes a distorted octahedral geometry; the pyridyl groups and the sulfur atoms are in trans position. The reaction of the complex 2 and hydrogen peroxide resulted to the oxidation of CoII into CoIII and the thioether groups of the ligand to sulfinate groups with elimination of the central ethylenic group of pydadt. Thus, complex 2 was converted to bis[3-(2-pyridylmethylamino)ethanesulfinate] cobalt(III) complex (3) {[Co(pynso)2](ClO4) · 0.5H2O}. The X-ray crystal structure reveals that the compound 3 crystallizes in the triclinic space group with the same donor atoms (Npyridyl, Namine and S) belonging to the two ligands in cis-position. In aqueous solution, the stability constants of the Co(II) chelates with these two ligands, determined by potentiometry, show the formation of [Co(LH)]3+ and [CoL]2+ species in all cases. The chelating power of pydadt ligand is slightly greater than that of pydado.  相似文献   

18.
The synthesis of two nickel(II) complexes based on a central bridging triaminoguanidine scaffold and a capping ligand per metal ion is reported. When 2,2′-bipyridine (bipy) is utilized as co-ligand the complex [Ni3LBr(bipy)3(H2O)3]NO3 · 9H2O · 1.5DMF (1) is obtained which crystallizes in the hexagonal space group P63/m. Complex 1 shows an interesting supramolecular structure pattern with alternating hydrophilic and hydrophobic layers characterized by extensive hydrogen-bonding and π-π-stacking, respectively. With 2,4,6-(2-pyridyl)-1,3,5-triazine (tptz) as capping ligand, complex [Ni3LBr(tptz)3]ClO4 · 7H2O · 1.5DMF (2) is obtained. The magnetic susceptibility data can be fitted using an equilateral triangle model () with an isotropic coupling constant of J=-31.0±0.6 for 1 and for 2.  相似文献   

19.
The ligand 1,3-bis[3-(2-pyridyl)pyrazol-1-yl]propane (L8) has afforded six-coordinate monomeric and dimeric complexes [(L8)CoII(H2O)2][ClO4]2 (1), [(L8)NiII(MeCN)2][BPh4]2 (2), [(L8)NiII(O2CMe)][BPh4] (3), and . The crystal structures of 1, 2 · MeCN, 3, and 4 revealed that the ligand L8 is flexible enough to expand its coordinating ability by fine-tuning the angle between the chelating fragments and hence folds around cobalt(II)/nickel(II) centers to act as a tetradentate chelate, allowing additional coordination by two trans-H2O, cis-MeCN, and a bidentate acetate affording examples of distorted octahedral , , and coordination. The angles between the two CoN2/NiN2 planes span a wide range 23.539(1)° (1), 76.934(8)° (2), and 69.874(14)° (3). In contrast, complex 4 is a bis-μ-1,3-acetato-bridged (syn-anti coordination mode) dicobalt(II) complex [Co?Co separation: 4.797(8) Å] in which L8 provides terminal bidentate pyridylpyrazole coordination to each cobalt(II) center. To our knowledge, this report provides first examples of such a coordination versatility of L8. Absorption spectral studies (MeCN solution) have been done for all the complexes. Complexes 1-3 are uniformly high-spin. Temperature-dependent (2-300 K) magnetic studies on 4 reveal weak ferromagnetic exchange coupling between two cobalt(II) (S = 3/2) ions. The best-fit parameters obtained are: Δ (axial splitting parameter) = −765(5) cm−1, λ (spin-orbit coupling) = −120(3) cm−1, k (orbital reduction factor) = 0.93, and J (magnetic exchange coupling constant) = +1.60(2) m−1.  相似文献   

20.
Synthesis and single crystal X-ray structures of the first paramagnetic transition metal complexes containing chiral ethylenedithio-tetrathiafulvalene-oxazoline (EDT-TTF-OX) 1a-c and ethylenedithio-tetrathiafulvalene-thiomethyloxazoline 2 (EDT-TTF-(SMe)OX) ligands based on copper (II) and cobalt (II) are described. The racemic [EDT-TTF-OX][Cu(hfac)2] complex 3a crystallizes in the triclinic centrosymmetric space group , whereas the enantiopure counterparts 3b-c crystallize in the triclinic non-centrosymmetric space group P1. Cu(II) adopts a distorted square pyramidal coordination geometry, a much weaker Cu?STTF interaction also being identified. The same coordination pattern around Cu(II) is observed in the complex [(rac)-EDT-TTF-(SMe)OX][Cu(hfac)2] (4) in spite of the bidentate nature of the redox active ligand. DFT theoretical calculations afforded two equilibrium configurations for a corresponding model complex, in which the metal centre establishes secondary coordination either with one STTF or with the SMe group. The same ligand coordinates the cobalt (II) to afford the octahedral complex [(rac)-EDT-TTF-(SMe)OX][Co(hfac)2] (5). In all these novel complexes, the paramagnetic centres are structurally and magnetically isolated. Cyclic voltammetry measurements show the stability of the radical cation species.  相似文献   

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