Rhodium macrocyclic complexes: The synthesis and single crystal X-ray structure of [Rh([18]aneN2S4)](PF6)3 · 3H2O ([18]aneN2S4 = 1,4,10,13-tetrathia-7,16-diazacyclooctadecane)

Reaction of[Rh(H₂O)₆]³⁺ with one molar equivalent of [18]aneN₂S₄ in refluxing MeOH-H₂O (1 : 1 v/v) for 12 h affords an orange solution from which the complex [Rh([18]aneN₂S₄)](PF₆)₃ can be isolated upon addition of NH₄PF₆. A single crystal X-ray structure determination shows a distorted octahedral geometry at rhodium(III) involving the four thioether and two aza-donors of the macrocycle. The complex cation adopts a rac-configuration via meridional coordination of the two SCH₂CH₂NCH₂CH₂S linkages.     

Crystal structure of a novel Hg(II) complex, [Hg(tri-2-furylphosphine)2(tri-2-furylphosphinoxide)3] [ClO4]2

The Hg(II) complex [Hg(TFP)₂(OTFP)₃][ClO₄]₂ with TFP=tri-2-furyl-phosphine and OTFP=tri-2-furylphosphinoxide has been prepared and characterised. It crystallises in the hexagonal P6₃/m space group with Z=2, a=13.308(3), c=21.092 (4) Å, V=3235(1) Å³. The structure of the complex cation consists of independent molecules with Hg pentacoordinated in exact trigonal bipyramidal geometry.     

Copper thioether chemistry: The synthesis and single crystal X-ray structures of [Cu2([18]aneS6)(NCMe)2](ClO4)2 and [Cu([9]aneS3)(AsPPh3)](ClO4)

Reaction of [18]aneS₆ with two molar equivalents of [Cu(NCMe)₄](ClO₄) in CH₂Cl₂-MeCN affords the binuclear copper(I) complex [Cu₂([18]aneS₆)(NCMe)₂](ClO₄)₂. The single crystal X-ray structure of the complex shows a centrosymmetric cation with two tetrahedral copper(I) centres each coordinated to three thioether S-donors of [18]aneS₆,Cu---S(1) = 2.3200(15), Cu---S(4) = 2.3415(16), Cu---S(7) = 2.3250(15) Å, and to one MeCN molecule, Cu---N(1) = 1.939(5) Å, to give an overall NS₃-donation at the metal centres. Additionally, S(7′) shows a long-range interaction, Cu …S(7′) = 3.318(2) Å thus distorting the coordination geometry of the metal ion towards trigonal bipyramidal. The metal-metal separation of 4.428(2) Å suggests that there is no significant interaction between the copper centres of the dimer. Reaction of [9]aneS₃ with one molar equivalent of [Cu(NCMe)₄](ClO₄) in refluxing MeCN in the presence of ligands, L, affords the adducts [Cu([9]aneS₃)L]⁺ (L = PPh₃, AsPh₃). The single crystal X-ray structure of the complex [Cu([9]aneS₃)(AsPh₃)](ClO₄) shows tetrahedral AsS₃ coordination at copper(I) with [9]aneS₃ bound facially to the metal centre, Cu---S = 2.303(6), Cu---As = 2.322(4) Å.     

Azamacrocyclic stabilization of SbCl2: synthesis and crystal structure of [SbCl2(Me3[9]aneN3)][SbCl6] showing explicit Sb lone-pair stereochemical activity. Me3[9]aneN3 = 1,4,7-trimethyl-1,4,7-triazacyclononane

The reaction of antimony(III)chloride and antimony(V)chloride in acetonitrile in the presence of the azamacrocyclic ligand Me₃[9]aneN₃ provides the golden-yellow ionic compound [SbCl₂(Me₃[9]aneN₃][SbCl₆]. X-ray structural characterization reveals the cation as five-coordinate with Ψ-octahedral metal geometry featuring a cis-SbCl₂⁺ unit coordinated to the three donor nitrogen atoms of the ligand (fac) and a stereochemically active lone pair occupying the sixth site in a trans-position to a ring nitrogen atom.     

Some further studies of estertin compounds. crystal structures of [NEt4][MeO2CCH2CH2Sn(dmio)2] (dmio = 1,3-dithiole-2-one-4,5-dithiolato) and (MeO2CCH2CH2)2SnX2[X2 = I2, (NCS)2 or Cl, Br]

Estertn compounds, (MeO₂CCH₂CH₂)₂SnX₂ [X₂ = I₂ (2); X₂ = Br₂ (9); X₂ = Cl, Br (4)) or X₂ = (NCS)₂ (3)] have been obtained by halide exchange reactions of (MeO₂CCH₂CH₂)₂SnCl₂. Crystal structure determinations of 2–4 revealed chelating MeO₂CCH₂CH₂ units with distorted octahedral geometries at tin. The Sn---O bond lengths in the isothiocyanato complex, 3, are shorter [2.390(11) to 2.498(12), mean 2.439 Å], with the chelate bite angles, C---Sn---O, larger [74.3(7) to 78.2(6), mean 76.0°] than those in the halide analogues 2 and 4 [Sn---O = 2.519(2) to 2.541(8), mean 2.530 Å; C---Sn---O 72.8(3) to 73.9(4), mean 73.3°]. ¹H, ¹³C and ¹¹⁹Sn NMR and IR spectra of 2–4 and 9 were determined in CDCl₃ solution: the NMR spectra of (MeO₂CCH₂CH₂)₂SnX₂ show the following trends: (i) both δ¹H and δ¹³C, increase and (ii) both ²J (Sn---H) and ¹J(Sn---C) decrease in the sequence X₂ = (NCS)₂, Cl₂, ClBr, Br₂ and I₂. The MeO₂CCH₂CH₂ and dmio groups (dmio = 1,3-dithiole-2-one-4,5-dithiolato) are all chelating groups in (MeO₂CCH₂CH₂)₂Sn(dmio) (5). As shown by X-ray crystallography, the tin atom in the anion of solid [Q][MeO₂CCH₂CH₂Sn(dmio)₂] 6 (Q = NEt₄) forms 5 strong bonds [to C and the 4 thiolato S atoms, Sn---S 2.459(2) to 2.559(2) Å], arranged in a near trigonal bipyramidal array. There is an additional Intramolecular but weaker, interaction with the carbonyl oxygen atom [Sn---O = 3.111(5) Å]; v(C=O) = 1714 cm⁻¹ in solid 6 (Q = NEt₄). NMR spectra of 5 and 6 are also reported.     

Synthesis, crystal structure and third-order non-linear optical property of heterobimetallic cluster compound [MoOICu3S3(2,2′-bipy)2]

Nest-shaped cluster [MoOICu₃S₃(2,2′-bipy)₂] (1) was synthesized by the treatment of (NH₄)₂MoS₄, CuI, (n-Bu)₄NI, and 2,2′-bipyridine (2,2′-bipy) through a solid-state reaction. It crystallizes in monoclinic space group P2₁/n, a=9.591(2) Å, b=14.820(3) Å, c=17.951(4) Å, β=91.98(2)°, V=2549.9(10) ų, and Z=4. The nest-shaped cluster was obtained for the first time with a neutral skeleton containing 2,2′-bipy ligand. The non-linear optical (NLO) property of [MoOICu₃S₃(2,2′-bipy)₂] in DMF solution was measured by using a Z-scan technique with 15 ns and 532 nm laser pulses. The cluster has large third-order NLO absorption and the third-order NLO refraction, its ₂ and n₂ values were calculated as 6.2×10⁻¹⁰ and −3.8×10⁻¹⁷ m² W⁻¹ in a 3.7×10⁻⁴ M DMF solution.     

Second-sphere coordination in the complex [Mn(H2O)6]2[thiacalix[4]arene tetrasulfonate]

The title calixarene, dimanganese thiacalix[4]arene tetrasulfonate, was prepared and its crystal structure was determined. [Mn(H₂O)₆]₂[thiacalix[4]arene tetrasulfonate]·0.5H₂O crystallizes in the monoclinic system, P2(1)/m space group, with a=13.014 (6), b=14.146 (9), c=13.184 (7) Å, β=113.307 (10)°, V=2229 (2) Å³ and Dc=1.710 gcm⁻³, Z=2. The title calixarene exists in the solid state as bilayer structure. The hydrophobic organic layer consists of thiacalix[4]arene tetrasulfonate in an up-down fashion, whereas, the hydrophilic inorganic layer consists of hexaaquamanganese (II) which is linked to the former through a second-sphere coordination.     

Das Reaktionsverhalten von Cp2NbCl2 gegenüber WF6—Struktur von [Cp2NbCl2]4[WF6]2[WCl6]

The oxidation of Cp₂NbCl₂ with pure WF₆ in SO₂ solution yielded the cationic metallocene species [Cp₂NbCl₂]⁺[WF₆]⁻ essentially in quantitative yield. The same reaction carried out in the presence of either equimolar amounts or a two-fold excess of HCN led to the preparation of the new niobocenium salt [Cp₂NbCl₂]₄⁺[WF₆]²⁻ which was studied by single crystal X-ray diffraction. This compound represents the first example of a structurally characterized metallocene-WF₆⁻ complex, and crystallizes in the tetragonal system: space group, P4₁2₁2(No. 92), a = 11.083(8) Å, c = 48.285 (9) Å; Z = 8; R = 0.0759, R_W = 0.0841. ab]Die Oxidation von Cp₂NbCl₂ mit reinem WF₆ führt in SO₂-Lösung zur Synthese von [Cp₂NbCl₂ ]⁺[WF₆]⁻ in nahezu quantitativer Ausbeute. Die analoge Reaktion führt unter Anwesenheit der äquimolaren Menge oder eines zweifachen Überschusses an HCN zur Ausbildung des Niobocenium-Komplexsalzes [Cp₂NbCl₂]₄⁺ [WF₆]₂⁻[WCl₆]²⁻, von dem eine Röntgenstrukturanalyse angefertigt wurde. Diese Verbindung repräsentiert den ersten structurell charakterisierten Vertreter eines Metallocen-WF₆⁻-Komplexes und kristallisiert im tetragonalen System: Raumgruppe P4₁2₁2 (Nr. 92), a = 11.083(8) Å, c = 48.285(9) Å; Z = 8; R = 0.0759, R_W = 0.0841. kw]Niobium; X-ray diffraction; Oxidation; Metallocenes     

Hydrothermal synthesis, crystal structure and characterization of [Zn(H2O)4]2 [H2As6V15O42(H2O)]·2H2O

The compound [Zn(H₂O)₄]₂[H₂As₆V₁₅O₄₂(H₂O)]·2H₂O (1) has been synthesized and characterized by elemental analysis, IR, ESR, magnetic measurement, third-order nonlinear property study and single crystal X-ray diffraction analysis. The compound 1 crystallizes in trigonal space group R3, a=b=12.0601(17) Å, c=33.970(7) Å, γ=120°, V=4278.8(12) Å³, Z=3 and R1(wR2)=0.0512 (0.1171). The crystal structure is constructed from [H₂As₆V₁₅O₄₂(H₂O)]⁴⁻ anions and [Zn(H₂O)₄]²⁺ cations linked through hydrogen bonds into a network. The [H₂As₆V₁₅O₄₂(H₂O)]⁶⁻ cluster consists of 15 VO₅ square pyramids linked by three As₂O₅ handle-like units.     

Structures of propionaldehyde, butyraldehyde, and pivalaldehyde complexes of the chiral rhenium fragment [(η-C5H5)Re(NO)(PPh3)]

The crystal structures of propionaldehyde complex (RS,SR)-(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₃)]⁺ PF₆⁻ (1b⁺ PF₆^s−; monoclinic, P2₁/c (No. 14), a = 10.166 (1) Å, b = 18.316(1) Å, c = 14.872(2) Å, β = 100.51(1)°, Z = 4) and butyraldehyde complex (RS,SR)-[(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHCH₂CH₂CH₃)]⁺ PF₆⁻ (1c⁺PF₆⁻; monoclinic, P2₁/a (No. 14), a = 14.851(1) Å, b = 18.623(3) Å, c = 10.026(2) Å, β = 102.95(1)°, Z = 4) have been determined at 22°C and −125°C, respectively. These exhibit C O bond lengths (1.35(1), 1.338(5) Å) that are intermediate between those of propionaldehyde (1.209(4) Å) and 1-propanol (1.41 Å). Other geometric features are analyzed. Reaction of [(η⁵-C₅H₅)Re(NO)(PPh₃)(ClCH₂Cl)]⁺ BF₄⁻ and pivalaldehyde gives [(η⁵-C₅H₅)Re(NO)(PPh₃)(η²-O=CHC(CH₃)₃)]⁺BF₄⁻ (81%), the spectroscopic properties of which establish a π C O binding mode.     

Copper thioether chemistry: Synthesis and X-ray crystal structures of binuclear copper(I) complexes [Cu2(L)] {L = [24]aneS8, [28]aneS8} incorporating octathia macrocycles

Reaction of L {L = [24]aneS₈, [28]aneS₈} with two molar equivalents of [Cu(NCMe)₄]X (X⁻ = ClO₄⁻, BF₄⁻, PF₆⁻) in MeCN affords the white binuclear copper(I) complexes [Cu₂(L)]²⁺. A single crystal X-ray structure determination of [CU₂([24]aneS₈)](BF₄)₂ shows two tetrahedral copper(I) centres, each of which is coordinated to four thioether sulphur-donors, Cu---S(1) = 2.263(3), Cu---S(4) = 2.363(3), Cu---S(7) = 2.349(3), Cu---S(10) = 2.261(3) Å. The Cu … Cu distance is 5.172(3) Å. A single crystal X-ray structure determination Of [CU₂([28]aneS₈)](ClO₄)₂ shows that this complex also contain two tetrahedral copper(I) centres, each coordinated to four thioether sulphur-donors, Cu---S(1) = 2.278(5), Cu---S(4) = 2.333(5), Cu---S(8) = 2.328(5), CU---S(11) = 2.268(5) Å. The Cu … Cu distance of 6.454(3) Å is greater than in [CU₂([24]aneS₈)]²⁺ , reflecting the greater cavity size in [CU₂([28]aneS₈)]²⁺. Cyclic voltammetry of [CU₂([24]aneS₈)]²⁺ and [CU₂([28]aneS₈)]²⁺ at platinum electrodes in MeCN (0.1 M ⁿBU₄NPF₆) shows irreversible oxidations at E_pa, = +0.88 V, +0.92 V vs Fc/Fc⁺, respectively, at a scan rate of 200 mV s⁻¹. Coulometric measurements in MeCN confirm these oxidations to be two-electron (one electron per copper) processes to give binuclear copper(II) species. Oxidation of the binuclear copper(I) precursors with H₂SO₄ or HNO₃ affords ESR-active copper(II) species which presumably incorporate SO₄²⁻ and NO₃⁻ bridges.     

The co-stacking of a planar metal complex and a novel 1,3-dithiole: The synthesis and crystal structure of [Pt(mnt)(CNMe)2]·(NC)2C2S2

The reaction of [NBu₄ⁿ]2Cu(mnt)₂] with [Pt(CNMe)₄][PF₆]₂ gives [Pt(mnt)(CNMe)₂]·(NC)₂C₂S₂CNMe, an X-ray study of which reveals co-stacking of neutral planar metal and organic molecules.     

Structural and spectroscopic properties of Hexamethylenetetramine cobalt(II) complex: [Co(NCS)2(hmt)2(H2O)2][Co(NCS)2(H2O)4] (H2O)

Synthesis, structure, spectroscopy and thermal properties of complex [Co(NCS)₂(hmt)₂(H₂O)₂][Co(NCS)₂(H₂O)₄] (H₂O) (I), assembled by hexamethylenetetramine and octahedral Co(II) metal ions, are reported. Crystal data for I: F_w 387.34, a=9.020(8), b=12.887(9), c=7.95(1) Å, =96.73(4), β=115.36(5), γ=94.16(4)°, V=820(1) Å³, Z=2, space group=P−1, T=173 K, λ(Mo-K)=0.71070 Å, ρ_calc=1.718567 g cm⁻³, μ=17.44 cm⁻¹, R=0.088, R_w=0.148. An interesting two-dimensional network is assembled via hydrogen bonds through coordinated and free water molecules. The d–d transition energy levels of Co(II) ion are determined by UV–vis spectroscopy and calculated by ligand field theory. The calculated results agree well with experiment ones.     

Structural characterisation of [Pt(NH3)4]2[W(CN)8][NO3]·2H2O donor–acceptor complex

The bimetallic [Pt(NH₃)₄]₂[W(CN)₈][NO₃]·2H₂O is characterised by single-crystal X-ray diffraction [S.G.P2₁/m(11), a=8.0418(7), b=19.122(2), c=9.0812(6) Å, Z=2]. All platinum centres have the square-plane D_4h geometry with average dimensions Pt(1)–N 2.042(2) and Pt(2)–N 2.037(10) Å. The octacyanotungstate anion has the square-antiprismatic D_4d configuration with average dimensions W(1)–C 2.164(13), C–N 1.140(12), W(1)–N 3.303(5) Å. The structure exhibits two different mutual orientations of Pt versus W units resulting in Pt(2)–W(1), W(1)^* separations of 4.77(2), 4.55(2)^* and Pt(1)–W(1) of 6.331(8) Å. A centrosymmetric structure reveals groups of two distinct columns: the first is formed by intercalated NO₃⁻ between parallel [Pt(1)(NH₃)₄]²⁺ planes and the second consists of [W(CN)₈]³⁻ interlayered by, parallel to square faces of W-antiprisms, [Pt(2)(NH₃)₄]²⁺. The structure is stabilised through a three-dimensional hydrogen bond network via nitrogen atoms of cyanide ligands, hydrogen atoms of NH₃ ligands, water molecules and oxygen atoms of NO₃⁻ counteranions. The vibrational pattern and the range of ν(CN) frequencies attributable to the electronic environment of W(V) and W(IV) are consistent with the ground state Pt(II)↔W(V) charge transfer.     

Synthesis and molecular structure of Ba5(μ5-OH)[μ3-OCH(CF3)2]4[μ2-OCH(CF3)2]4 [OCH(CF3)2](THF)4(H2O)·THF: a source of barium fluoride

The reaction between metallic barium and fluoroisopropanol or alcoholysis of [Ba(OPrⁱ)₂] produces a pentanuclear fluoroalkoxide. Its X-ray structure determination showed its formulation to correspond to Ba₅(μ₅-OH)[μ₃-OCH(CF₃)₂]₄[μ₂-OCH(CF₃)₂]₄ [OCH(CF₃)₂](THF)₄(H₂O)·THF. The metallic core is based on a square pyramid encapsulating an hydroxo ligand. In addition to the barium---alkoxide bonds [2.53(3)–2.86(3) Å] neutral O-donors, four THF [2.82(2)–2.86(3) Å] and one H₂O [2.79(3) Å] and secondary barium---fluorine interactions [2.99(2)–3.31(2) Å] ensure high coordination numbers, from 9 to 11 for the metal centers. Hydrogen bonding between the apical fluoroisopropoxide, the water molecule and one THF molecule, non-bonded to a metal center, accounts for the stability of the hydrate and illustrates the Lewis acidity of fluoroalkoxides. Thermal decomposition leads to BaF₂.     

Hydrothermal syntheses and crystal structures of bimetallic cluster complexes [{Cd(phen)2}2V4O12]·5H2O and [Ni(phen)3]2[V4O12]·17.5H2O

The hydrothermal reactions of vanadium oxide starting materials with divalent transition metal cations in the presence of nitrogen donor chelating ligands yield the bimetallic cluster complexes with the formulae [{Cd(phen₂)₂V₄O₁₂]·5H₂O (1) and [Ni(phen)₃]₂[V₄O₁₂]·17.5H₂O (2). Crystal data: C₄₈H₅₂Cd₂N₈O₂₂V₄ (1), triclinic. a=10.3366(10), b=11.320(3), c=13.268(3) Å, =103.888(17)°, β=92.256(15)°, γ=107.444(14)°, Z=1; C₇₂H₁₃₁N₁₂Ni₂O_29.5V₄ (2), triclinic. a=12.305(3), b=13.172(6), c=15.133(4), =79.05(3)°, β=76.09(2)°, γ=74.66(3)°, Z=1. Data were collected on a Siemens P4 four-circle diffractometer at 293 K in the range 1.59° <θ<26.02° and 2.01°<θ<25.01° using the ω-scan technique, respectively. The structure of 1 consists of a [V₄O₁₂]⁴⁻ cluster covalently attached to two {Cd(phen)₂}²⁺ fragments, in which the [V₄O₁₂]⁴⁻ cluster adopts a chair-like configuration. In the structure of 2, the [V₄O₁₂]⁴⁻ cluster is isolated. And the complex formed a layer structure via hydrogen bonds between the [V₄O₁₂]⁴⁻ unit and crystallization water molecules.     

The synthesis, vibrational spectroscopy, and crystal and molecular structure of [H3NCH2CH2NH3][PdBr6]

The complex [H₃NCH₂CH₂NH₃][PdBr₆] has been isolated as well-formed brown crystals. The Raman (single crystal) and FTIR (wax disc) spectra of the complex have been recorded but the band assignments are complicated by extensive factor group splitting and resonance effects. The crystal belongs to space group Pnnm, with Z = 2, each ion occupying sites of 2/m (C_2h) symmetry. The [PdBr₆]²⁻ ion is very close to octahedral, the two unique PdBr distances, 2.466(3) and 2.470(3) Å, being equal within experimental error and the BrPdBr angles being 90 ± 0.8°. The diammonium cation has an extended, planar, trans structure.     

Preparation and structure of a ruthenium dicarbonyl derivative of the P2N4S2 ring

The reaction of Ru(CO)₄(C₂H₄) or Ru(CO)₅ with 1,5-Ph₄P₂N₄S₂ in CH₂Cl₂/hexane at 23°C produces the dimer [Ru(CO)₂(Ph₄ P₂N₄S₂)]₂ (2), which was shown by X-ray crystallography to have a centrosymmetric structure in which the P₂N₄S₂ ring is attached to one ruthenium atom through two (geminal) nitrogen atoms and the remote sulfur atom and serves as a bridge to the other ruthenium atom via the second sulfur atom. Crystals of 2 ·2(CH₂Cl₂) are triclinic, space group P (No. 2), a = 12.901(1) Å, b = 13.072(1) Å, c = 10.123(1) Å, = 100.88(1)°, β = 98.90(1)°, γ = 67.50(1)°, V = 1542.4(3) Å, Z = 1 with final R and R_w values of 0.040 and 0.027, respectively.     

A localized molecular orbital study on the bonding of> Mo3S4]2Mo> and> Mo3S4]CuI> versus (C6H6)2Cr and C6H6Cr(CO)3

The energy-localized CNDO/2 molecular orbitais have been calculated for the clusters containing molybdenum, > {Mo₃S₄₂Mo}⁸⁺ and> Mo₃S₄]CuI> ⁴⁺, versus the prototype arene-metal sandwich (C₆H₆)₂Cr and half-sandwich complexes C₆H₆Cr(CO)₃. The bonding characteristics of these compounds are described from a localization bonding viewpoint. There are two typical M-arene and M-[Mo₃S₄] bondings. One is formed by electron donation from the three-center two-electron π-bonds in the arene or [Mo₃S₄]⁴⁺ ligands into the vacant hybrid orbitais of the “stranger” metal atom. In the other M-arene or M-[Mo₃S₄] bond there is very little donation by the lone electron pair occupying the d AOs of the “stranger” metal atom to the arene or [Mo₃S₄]⁴⁺ ligands. The analogy of the ligand [Mo₃S₄]⁴⁺ in the clusters studied with the ligand benzene is also briefly discussed.     

The syntheses of phenol-containing diazamacrocycles and liquid membrane transports of alkali cations

Two new bisphenol-containing diazacrown ether derivatives, 7,16-bis(2-hydroxy-5-ethylbenzoatebenzyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (1) and 7,16-bis(2-hydroxy-3,4-dimethylbenzyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (2), have been synthesized via one-pot Mannich reaction. The compound 1 is structurally characterized. The liquid membrane transports of alkali metal cations using these two new diazamacrocycles and the other previously prepared diazamacrocyclic derivative 7,16-bis(3-hydroxy-6-methyl-2-pyridylmethyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane (3) as ion-carriers are also studied. The results show that the rates of cation transports are closely related to the number of nitrogen donors and the steric effect of the substituted groups. Compared with other macrocyclic compounds, compound 1 shows a good selectivity for Li⁺, therefore providing a new efficient carrier for Li⁺ extraction.