Di‐Benzo‐18‐Crown‐6 and its Derivatives as Ligands in the Search for Ion Channels

Based on the previously reported one‐dimensional channel system [(H₂O)?(DB18C6)(μ₂‐H₂O)_2/2][(H₃O)?(DB18C6)(μ₂‐H₂O)_2/2]I₃ ( 2 ), which is realized by stacking of crown ether molecules (DB18C6 = dibenzo‐18‐crown‐6), other synthetic approaches towards ionic channels and their results are presented in this paper. The “cutting out” approach using DB18C6 as scissor, applied on NaI, yields the compound [Na?(DB18C6)I(THF)][Na?(DB18C6)(H₂O)₂]I(THF)₂(CHI₃) ( 1 ), in high yield. It is based on a neutral and a cationic complex of sodium by DB18C6 linked via H‐bonding to give short chain fragments. The anion exchange approach, trying to replace I₃^? by Br₃^? leads to the intercalation of a cation into a DB18C6 chain in [(Me₃NPh)(DB18C6)]Br₃ ( 3 ). A similar reaction as for the synthesis of 2 , but replacing iodide with bromine, yields finally a brominated DB18C6 ligand. In the presence of iron, the compound [(H₅O₂)?(Br₄‐DB18C6)₂][FeBr₄], 4 , is observed, in which a H₅O₂⁺‐cation is encapsuled by two brominated crown ether molecules. The absence of Fe and an excess of Br₂ leads to the complexation of H₃O⁺, and co‐crystallisation of bromine in [(H₃O)?(Br₄‐DB18C6)]Br₃Br₂ ( 5 ).     

Synthesis and Structure of Different-Metal Different-Ligand Germanium(IV) and Cobalt(II) or Copper(II) Complexes with 1-Hydroxyethylidenediphosphonic Acid and 1,10-Phenanthroline

Different-metal different-ligand complexes [{Co(Phen)₃}₂{Co(Phen)(H₂O)₄}₂][{Ge(μ-OH)(μ- Hedp)}₆Cl₂] (I), [{Cu(Phen)₂(H₂O)}₂(HPhen)₂][Ge(μ-OH)(μ-Hedp)]₆ · 20H₂O (II) (H₄Hedp = 1-hydroxyethylidenediphosphonic acid, Phen = 1,10-phenanthroline) were synthesized and studied by X-ray diffraction. According to X-ray diffraction data (CIF files CCDC nos. 1573112 (I), 1573113 (II)), compounds I and II are cation–anion type complexes in which the anions are represented by {[Ge(μ-OH)(μ-Hedp)]⁶}^6– and, in the case of I, two additional Cl^– ions, while the cations are [Co(Phen)₃]²⁺, [Co(Phen)(H₂O)₄]²⁺ in I and [Cu(Phen)₂(H₂O)]²⁺, HPhen⁺ in II. In the crystals of compounds I and II, the cations, anions, and water molecules are combined by numerous intermolecular hydrogen bonds, giving rise to a 3D network.     

Chalcogen–acetylide interaction and unusual reactivity of coordinated acetylide with water: synthesis and characterisation of [(η5-C5R5)Fe3(CO)6(μ3-E)(μ3-ECCH2RI)] (R=H,Me; RI=Ph,Fc; E=S,Se) and [(η5-C5R5)MoFe2(CO)6(μ3-S)(μ-SCCH2Ph)] (R=H,Me)

Photolysis of a benzene solution containing [Fe₃(CO)₉(μ₃-E)₂] (E=S, Se), [(η⁵-C₅R₅)Fe(CO)₂(CCR^I)] (R=H, Me; R^I=Ph, Fc), H₂O and Et₃N results in formation of new metal clusters [(η⁵-C₅R₅)Fe₃(CO)₆(μ₃-E)(μ₃-ECCH₂R^I)] (R=H, R^I=Ph, E=S 1 or Se 2; R=Me, R^I=Ph, E=S 3 or Se 4; R=H, R^I=Fc, E=S 5; R=Me, R^I=Fc, E=S 6 or Se 7). Reaction of [Fe₃(CO)₉(μ₃-S)₂]with [(η⁵-C₅R₅)Mo(CO)₃(CCPh)] (R=H, Me), under same conditions, produces mixed-metal clusters [(η⁵-C₅R₅)MoFe₂(CO)₆(μ₃-S)(μ-SCCH₂Ph)] (R=H 8; R=Me 9). Compounds 1–9 have been characterised by IR and ¹H and ¹³C-NMR spectroscopy. Structures of 1, 5 and 9 have been established crystallographically. A common feature in all these products is the formation of new C-chalcogen bond to give rise to a (ECCH₂R^I) ligand.     

New high-dimensional networks based on polyoxometalate and crown ether building blocks

Three novel supramolecular assemblies constructed from polyoxometalate and crown ether building blocks, [(DB18C6)Na(H(2)O)(1.5)](2)Mo(6)O(19).CH(3)CN, 1, and [(Na(DB18C6)(H(2)O)(2))(3)(H(2)O)(2)]XMo(12)O(40).6DMF.CH(3)CN (X = P, 2, and As, 3; DB18C6 = dibenzo-18-crown-6; DMF = N,N-dimethylfomamide), have been synthesized and characterized by elemental analyses, IR, UV-vis, EPR, TG, and single crystal X-ray diffraction. Compound 1 crystallizes in the tetragonal space group P4/mbm with a = 16.9701(6) A, c = 14.2676(4) A, and Z = 2. Compound 2 crystallizes in the hexagonal space group P6(3)/m with a = 15.7435(17) A, c = 30.042(7) A, gamma = 120 degrees, and Z = 2. Compound 3 crystallizes in the hexagonal space group P6(3)/m with a = 15.6882(5) A, c = 29.9778(18) A, gamma = 120 degrees, and Z = 2. Compound 1 exhibits an unusual three-dimensional network with one-dimensional sandglasslike channels based on the extensive weak forces between the oxygen atoms on the [Mo(6)O(19)](2)(-) polyoxoanions and the CH(2) groups of crown ether molecules. Compounds 2 and 3 are isostructural, and both contain a novel semiopen cagelike trimeric cation [(Na(DB18C6)(H(2)O)(2))(3)(H(2)O)(2)](3+). In their packing arrangement, an interesting 2-D "honeycomblike" "host" network is formed, in which the [XMo(12)O(40)](3)(-) (X = As and P) polyoxoanion "guests" resided.     

Structural and spectroscopic characterization of the dirhenium acetamidate products resulting from the hydrolysis of acetonitrile

Unsaturated molecules such as nitriles are activated upon coordination to a dirhenium core. Acetonitrile is hydrolyzed in the presence of water to produce coordinated bridging acetamidate ligands as demonstrated by the reaction of [N(C₄H₉)₄]₂[Re₂Cl₈] with CH₃CN and water in ethanol to form the acetamidate complexes, [N(C₄H₉)₄][Re₂Cl₅(μ-CH₃C(O)NH)(μ-CH₃C(OH)N)]·3CH₂Cl₂ [I] and Re₂Cl₄(μ-CH₃C(O)NH)(μ-dppm)₂·4 CH₂Cl₂/0.833 EtOH [II]. Compound II is formed when I is reduced upon coordination of bis(diphenylphosphino)methane (dppm). Compounds I and II were characterized using X-ray crystallography and a variety of other spectroscopic methods.     

Synthesis of [(μ2-η2-CHCHPh)(μ-S){Fe2(CO)6}2(μ4-S)]− and its reactions with electrophiles

The action of [(μ₂-η²-CHCHPh)(μ-CO)Fe₂(CO)₆]⁻ with (μ-S)₂Fe₂(CO)₆ gives the anionic complex [(μ₂-η²-CHCHPh)(μ-S){Fe₂(CO)₆}₂(μ₄-S)]⁻ (1). The anion 1 reacts with alkyl halides, acid chlorides and Cp(CO)₂FeI to yield neutral products (μ₂-η²-CHCHPh)(μ-RS)[Fe₂(CO)₆]₂(μ₄-S) (R=Me, 2a; Et, 2b; PhCH₂, 2c; PhC(O), 3a; PhCHCHC(O), 3b and Cp(CO)₂Fe, 4).     

Aluminum hydrides with radical-anionic and dianionic acenaphthene-1,2-diimine ligands

The reaction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-bian) with LiAlH₄ affords two products regardless of the solvent used (tetrahydrofuran or diethyl ether). These products were isolated as green and colorless crystals. Green crystals of the complex [(dpp-bian)Al(H)₂Li(THF)₃] (1) were obtained from tetrahydrofuran; colorless crystals of the complex [{dpp-bian(H₂)}Al(H)₂Li(Et₂O)₂] (2), from diethyl ether. The reactions of compound 1 with 2,6-di-tert-butyl-4-methylphenol and benzophenone gave monohydrides [(dpp-bian)Al(H)(OC₆H₂-2,6-Bu₂ ^t-4-Me)][Li(THF)₄] (3) and [(dpp-bian)Al(H)(OCHPh₂)- Li(THF)₂] (4), respectively. The diamagnetic aluminum hydride [(dpp-bian)AlH(THF)] (5) was synthesized by the reaction of dichloroalane HAlCl₂ (in situ) with the disodium salt of dpp-bian in THF; the paramagnetic hydride [(dpp-bian)AlH(Cl)] (6) containing the dpp-bian radical anion was synthesized by the reaction of the monosodium salt (dpp-bian)Na with monochloroalane H₂AlCl (in situ) in diethyl ether. The reaction of compound 6 with tert-butyllithium gives the complex [(dpp-bian)AlBu^t(Et₂O)] (7). Diamagnetic derivatives 1—5 and 7 were characterized by ¹Н NMR spectroscopy; paramagnetic compound 6, by ESR spectroscopy. The molecular structures of compounds 1—7 were determined by single-crystal X-ray diffraction.     

Synthesis and crystal structure of dibenzo-18-crown-6 oxonium perchlorate trihydrate

A hydrated crystalline ionized adduct of dibenzo-18-crown-6 and perchloric acid DB18C6 · H₃O⁺ · CiO ₄ ^? · 3H₂O (I) is synthesized and characterized by X-ray diffraction. The crystals of I are monoclinic: a = 17.760 Å, b = 12.922 Å, β = 124.27°, Z = 4, space group Cc. The structure of I is solved by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.079 for 3294 independent reflections (CAD4 automated diffractometer, λMoK _α radiation). A DB18C6 molecule has a butterfly conformation with the rough symmetry C _2v . An H₃O⁺ · H₂O dimer is situated on one side of the DB18C6 macrocycle, and the ClO ₄ ^? anion and two other water molecules are on the other side. In the crystal of I, the DB18C6 molecules, H₃O⁺ and ClO ₄ ^? ions, and water molecules are linked through intermolecular (interionic) hydrogen bonds to form broad infinite chains running along the z axis.     

Diaquabromo(18-crown-6)rubidium and triaqua(18-crown-6)barium dibromide monohydrate: Synthesis and crystal structures

Two complexes are synthesized: diaquabromo(18-crown-6)rubidium [RbBr(18-crown-6)(H₂O)₂] (I) and triaqua(18-crown-6)barium dibromide monohydrate [Ba(18-crown-6)(H₂O)₃]²⁺ 2Br^? · H₂O (II). The orthorhombic structure of compound I (space group Pnma, a = 10.124 Å, b = 15.205 Å, c = 12.544 Å, Z = 4) and the monoclinic structure of compound II (space group C 2/c, a = 17.910 Å, b = 10.315 Å, c = 14.879 Å, β = 123.23°, Z = 4) are determined by a direct method and refined by the full-matrix least-squares method in the anisotropic approximation to R = 0.063 (I) and 0.042 (II) for all 2293 (I) and 3363 (II) independent measured reflections (CAD-4 automated diffractometer, λMoK _α). The complex molecule [RbBr(18-crown-6)(H₂O)₂] in compound I and the randomly disordered cation [Ba(18-crown-6)(H₂O)₃]²⁺ in compound II are of the host-guest type: their Rb⁺ or Ba²⁺ cation (its coordination number is nine) is located in the cavity of the 18-crown-6 ligand and coordinated by all six O atoms. In structure I, the coordination polyhedron of Rb⁺ is a distorted hexagonal pyramid with a triple apex at the Br^? ligand and two O atoms of the water molecules. In structure II, the Ba²⁺ polyhedron is a distorted hexagonal bipyramid with one apex at the O atom of the water molecule and the other split apex at two O atoms of water molecules.     

Crystal structures of the dicyclohexyl-(18-crown-6) uranyl perchlorate complex and of its hydrolysis product

The structures of dicyclohexyl-(18-crown-6) uranyl perchlorate, [(C₂₀H₃₆O₆)UO₂] (ClO₄)₂ (complex I) and of dicyclohexyl-(18-crown-6) uranyl hydroxyperchlorate [C₂₀H₃₆O₆]₃ [(UO₂)₂(H₂O)₆] · (ClO₄)₂, CH₃CN, (complex II) have been determined from three dimension X-ray diffraction data.The uranyl group is directly coordinated to the oxygen atoms of the polyether ring in complex I; its hydrolysis (complex II) leads to a dimerization of the uranyl ions by sharing two OH groups with an U-U distance of only 3.827(8) Å. The polyether molecules are connected by hydrogen bonds with the dimeric ion [(UO₂)₂ (OH)₂ (H₂O)₆]²⁺.     

Polymeric heterometallic CuII dimethylmalonate complexes with potassium and cadmium ions

A reaction of (HPiv)₂Cu₂(Piv)₄ with dimethylmalonic acid dipotassium salt (K₂Me₂mal) leads to the formation of a cage coordination polymer {(μ-H₂O)₆K₈[(μ-H₂O)Cu-(μ₃,κ²-Me₂mal)(μ₆,κ²-Me₂mal)]₂[Cu₂(μ₅,κ²-Me₂mal)₂(μ₅,κ²-Me₂mal)₂]}n (1). It was found that when 1 reacted with CdSO₄·8H₂O in a mixture of EtOH-H₂O (3: 1), the potassium ions in 1 were displaced with cadmium(ii) ions with the formation of a heterometallic 1D-polymer [(κ¹-H₂O)₄CdCu(μ,κ²-Me₂mal)₂] _n (2). Compounds 1 and 2 were characterized by X-ray crystallography and ESR spectroscopy.     

Protophilicity,electrochemical property,and desulfurization of diiron dithiolate complexes containing a functionalized C2 bridge with two vicinal basic sites

Two diiron dithiolate complexes [{μ-SC(NBn)CH(NHBn)S-μ}Fe₂(CO)₅L] (L = PPh₃, 2; P(Pyr)₃, 3) containing a functionalized C₂ bridge with two vicinal basic sites were prepared and characterized as models of the FeFe-hydrogenase active site. The molecular structures of 2 and its N-protonated form [(2H_N)(OTf)] were determined by X-ray analyses of single crystals. In the solid state of [(2H_N)(OTf)]. Each asymmetric unit contains a molecule of [(2H_N)(OTf)] and a molecule of water. The molecule of water is close to the iron atom of the [Fe(CO)₃] unit (Fe···O(H₂O), 4.199 Å). The complexes 2 and 3 are relatively protophilic. ³¹P NMR spectra and cyclic voltammograms show that they can be protonated by the mild acids CCl₃COOH and CF₃COOH. Electrochemical studies show that the first reduction peak of 3 at ?1.51 V versus Fc⁺/Fc is 110 mV more positive than that (?1.62 V) found for the analogous diiron azadithiolate complex [{(μ-SCH₂)₂N(CH₂C₆H₅)}Fe₂(CO)₅P(Pyr)₃] (7). Protonation of 2 and 3 leads to the anodic shifts of 610–650 mV for the Fe^IFe^I/Fe^IFe⁰ reduction potentials. The shifts are apparently larger than that (450 mV) for protonation of 7. The reaction of the all-carbonyl complex [{μ-SC(NBn)CH(NHBn)S-μ}Fe₂(CO)₅L] with two equivalents of bis(diphenylphosphino)methane (dppm) in refluxing toluene affords a desulfurized complex [(μ-S)(μ-dppm)₂Fe₂(CO)₄] (6). The reaction process was studied. A dppm mono-dentate intermediate [{μ-SC(NBn)CH(NHBn)S-μ}Fe₂(CO)₅(κ¹-dppm)] (4) and a dppm μ-bridging species [{μ-SC(NBn)CH(NHBn)S-μ}Fe₂(CO)₄(μ-dppm)] (5) have been isolated and spectroscopically characterized.     

Nanometer Channels and Cages within the Extended Basic Mercurous Cations [(Hg2)3(OH)2]4+ and [(Hg2)2O]2+

The two‐ and three‐dimensional mercurous cations [(Hg₂)₃(OH)₂]⁴⁺ and [(Hg₂)₂O]²⁺ crystallize with channels and cages of roughly 1 nm diameter from aqueous solutions dependent upon the acidity of the solution. Crystal structures were determined, for example, for [Zn(H₂O)₆][(Hg₂)₃(OH)₂](NO₃)₆ (trigonal, space group P321, a = 1183.5(2) pm, c = 534.8(1) pm, Z = 1, R1 = 0.0351 for I₀ > 2σ(I₀)) and for [(Hg₂)₂O][Pb(NO₃)₃]₂ (cubic, space group , a = 1543.1(2) pm, Z = 8, R1 = 0.0534 I₀ > 2σ(I₀)).     

Synthesis and characterization of dinuclear pyrazolato bridged platinum(IV) complexes

Reactions of [PtMe₃(OCMe₂)₃](BF₄) and [(PtMe₃I)₄] with pyrazole (pzH) afforded mononuclear pyrazole platinum(IV) complexes [PtMe₃(pzH)₃](BF₄) (1) and [PtMe₃I(pzH)₂] (2), respectively. The formation of dinuclear pyrazolato bridged platinum(IV) complexes (PPN)[(PtMe₃)₂(μ-pz)₃] (3), (PPN)[(PtMe₃)₂(μ-I)(μ-pz)₂] · 1/2Et₂O (4) and [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (5) was achieved by the reaction of each 1 and 2 with [PtMe₃(OCMe₂)₃](BF₄) in the presence of KOAc followed by reaction with (PPN)Cl (PPN⁺ = bis(triphenylphosphine)iminium cation) and 18C6, respectively. The reaction of complex 4 with AgO₂CCF₃ followed by addition of RSR′ (R/R′ = Me/Me, Me/Ph) resulted in the formation of complexes [(PtMe₃)₂(μ-pz)₂(μ-RSR′)] (R/R′ = Me/Me, 6; Me/Ph, 7). All complexes were characterized unambiguously by microanalysis and NMR (¹H, ¹³C) spectroscopic investigations. Additionally, crystal structures of complexes 3 and 4 as well as DFT calculation are presented. Furthermore, in vitro studies on the anti-proliferative activity of complexes 2 and 5 were carried out.     

Lutetium gets a crown: Synthesis, structure and reaction chemistry of the separated ion pair complex, [Li(12-crown-4)2][(C5Me5)2LuMe2]

Reaction of (C₅Me₅)₂Lu(Me)(μ-Me)Li(THF)₃ (2) with excess 12-crown-4 affords the new separated ion pair complex, [Li(12-crown-4)₂][(C₅Me₅)₂LuMe₂] (3), in excellent yield. This complex reacts with 2,6-diisopropylaniline and phenylacetylene to give the methyl amide complex [Li(12-crown-4)₂][(C₅Me₅)₂Lu(Me)(NH-2,6-ⁱPr₂C₆H₃)] (4) and the bis(acetylide) complex [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5), respectively. Attempts to promote methane loss from complexes 3 and 4 to generate a lutetium methylidene or imido complex, respectively, were unsuccessful. The ability of the bis(acetylide) complex 5 to act as a π-tweezer complex was also explored. Reaction between [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5) and CuSPh gave only intractable lutetium products and the copper(I) species [Li(12-crown-4)₂][Cu(C≡C-Ph)₂] (8). The new lutetium complexes have been characterized by elemental analysis and NMR spectroscopy. Finally, the X-ray crystal structures of (C₅Me₅)₂Lu(Me)(μ-Me)Li(THF)₃ (2), [Li(12-crown-4)₂][(C₅Me₅)₂LuMe₂] (3), [Li(12-crown-4)₂][(C₅Me₅)₂Lu(Me)(NH-2,6-ⁱPr₂C₆H₃)] (4), [Li(12-crown-4)₂][(C₅Me₅)₂Lu(C≡C-Ph)₂] (5), and [Li(12-crown-4)₂][Cu(C≡C-Ph)₂] (8) are also reported.     

H-bonding of complex indium thiocyanates with crown ether molecules

Supramolecular ensembles [In(H₂O)₄(NCS)₂][In(H₂O)₂(NCS)₄] · 2(18C6) (I) and [In(H₂O)₃(NCS)₃] · 18C6 (II) are synthesized and identified by the data of elemental analyses, IR spectra, and X-ray structure analysis for structure I and X-ray phase analysis for structure II. In spite of specific features of the H-bonding of the 18C6 molecules with the cationic, molecular, or anionic indium complexes, chain motives are observed in structures I and II.     

A new Keggin-type heteropolyanion decorated with dinuclear copper-organic coordination ions: {[Cu(Phen)(μ-Cl)Cu(Phen)<Subscript>2</Subscript>]<Subscript>2</Subscript>[SiW<Subscript>12</Subscript>O<Subscript>40</Subscript>]} · H<Subscript>2</Subscript>O

A new Keggin-type heteropolyanion decorated with dinuclear copper-organic coordination ions, {[Cu(Phen)(μ-Cl)Cu(Phen)₂]₂[SiW₁₂O₄₀]}· H₂O (I), has been hydrothermally synthesized and structurally characterized by IR spectroscopy and single-crystal X-ray diffraction. X-ray crystallography analysis showed that two dinuclear copper-organic [Cu(Phen)(μ-Cl)Cu(Phen)₂]³⁺ units are supported on the reduced α-Keggin polyoxoanion [SiW₁₂O₄₀]^6? via two terminal oxygen atoms from opposite sides of the Keggin polyoxoanion, and I further acts as a neutral molecular unit for the construction of a one-dimensional chain-like framework by \(C - H \cdots Cl\) hydrogen bonds and π-π-stacking interactions.     

Organic carboxylate anions effect on the structures of a series of Mn(II) complexes based on 2-phenylimidazo[4,5-f]1,10-phenanthroline ligand

In our efforts to tune the structures of Mn(II) complexes by selection of organic carboxylic acid ligands, six new complexes [Mn(PIP)₂Cl₂] (1), [Mn(PIP)₂(4,4′-bpdc)(H₂O)]·2H₂O (2), [Mn(PIP)₂(1,4-bdc)] (3), [Mn(PIP)(1,3-bdc)] (4), [Mn(PIP)₂(2,6-napdc)]·H₂O (5), and [Mn(PIP)(1,4-napdc)]·H₂O (6) were obtained, where PIP=2-phenylimidazo[4,5-f]1,10-phenanthroline, 4,4′-H₂bpdc=biphenyl-4,4′-dicarboxylic acid, 1,4-H₂bdc=benzene-1,4-dicarboxylic acid, 1,3-H₂bdc=benzene-1,3-dicarboxylic acid, 2,6-H₂napdc=2,6-naphthalenedicarboxylic acid, 1,4-H₂napdc=1,4-naphthalenedicarboxylic acid. All complexes have been structurally characterized by IR, elemental analyses, and single crystal X-ray diffraction. Structural analyses show that complexes 1 and 2 possess mononuclear structures, complexes 3, 4, and 5 feature chain structures, and complex 6 exhibits a 2D (4,4) network. The structural difference of 1–6 indicates that organic carboxylate anions play important roles in the formation of such coordination architectures. Furthermore, the thermal properties of complexes 1–6 and the magnetic property of 4 have been investigated.     

Crystal and Molecular Structures of (Dibenzo-18-Crown-6)(Nitrato-O,O")-Tetrahydrofuranpotassium, [K(DB18C6)(THF)(NO3)]

The (dibenzo-18-crown-6)(nitrato-O,O")tetrahydrofuranpotassium complex [K(DB18C6)(THF)(NO₃)] (I) was synthesized and studied using X-ray diffraction analysis. The crystals are orthorhombic: a= 9.608 Å, b= 9.926 Å, c= 27.234 Å, Z= 4, space group P2₁2₁2₁. The structure was solved by the direct method and refined by the least-squares method in the anisotropic approximation to R= 0.099 over all 2620 measured independent reflections (CAD4 automated diffractometer, MoK radiation). Complex Iin the crystal exists as individual host–guest molecules, the K⁺cation (CN 9) being located in the DB18C6 macrocycle cavity and being coordinated to its six oxygen atoms and to two oxygen atoms of the nitrato ligand on one side of the macrocycle and to the THF oxygen atoms on the other side. The DB18C6 molecule in Ihas a butterfly conformation with approximate C _2V symmetry.     

Preparation of organozirconium aromatic compounds in mixed aqueous-organic solvents: X-ray structures of [Cp2ZrCl(μ2-O′,O′′C-C6H5)], [(CpZr)3(μ2-O′,O′′C-C6H3Cl2)3(μ3-OH)(μ2-OH)3](Cl2C6H3COO)2, and [(CpZr)3(μ2-O′,O′′C-C6H4Cl)3(μ3-OH)(μ2-OH)3]Cl2·CH2Cl2

A new and facile method is presented for the synthesis of zirconocene carboxylate compounds, in which zirconocene dichloride (Cp₂ZrCl₂) is dissolved in 1 M aqueous HCl solution and the requisite ligand is dissolved in an organic solvent. Five such compounds [Cp₂ZrCl(μ₂-O′,O′′C-C₆H₅)] (1), [Cp₂ZrCl(μ₂-O′,O′′C-C₆H₃Cl₂)] (2), [Cp₂Zr(μ₂-O′,O′′C-C₆H₃(OH)Cl)₂] (3), [Cp₂Zr(μ₂-O′,O′′C-C₆H₃(OH)(NO₂))₂] (4), and [Cp₂Zr(μ₂-O′,O′′C-C₆H(OH)Cl₃)₂] (5) have been obtained by this method. The effect of pH on the stability of Cp₂ZrCl₂ in 1 M HCl solution has been investigated by UV/vis spectrophotometry and ¹H NMR spectrometry. The results showed that the aqueous Cp₂ZrCl₂ solutions became less stable with increasing pH, liberating cyclopentadiene. Accordingly, at higher pH (～7), two trinuclear zirconium monocyclopentadienyl compounds, [(CpZr)₃(μ₂-O′,O′′C-C₆H₃Cl₂)₃(μ₃-OH)(μ₂-OH)₃](Cl₂C₆H₃COO)₂ (6) and [(CpZr)₃(μ₂-O′,O′′C-C₆H₄Cl)₃(μ₃-OH)(μ₂-OH)₃]Cl₂·CH₂Cl₂ (7), were obtained. All compounds 1–7 have been characterized by FT-IR, ¹H NMR spectra and elemental analysis. In all of the compounds, the aromatic acid acts as a bidentate ligand in coordinating to the zirconium; both chelating and bridging modes are observed. X-ray crystallographic studies on 1, 6, and 7 have revealed that the geometries at zirconium are distorted octahedral in 6 and 7, and distorted trigonal-bipyramidal in 1.