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The magnetic properties of three 1D copper(II) salts are reported. The compound Cu(14ane)Cu(N3)4 contains alternating site chains with weak FM coupling with J/k=0.635 K. Magnetization studies are reported on Cu(TIM)CuCl4, an alternating site, alternating FM/AFM exchange system with JFM/k=29.7 K and JAFM/k=-8.66 K. (HPy)2Cu3Cl8.2H2O contains FM chains composed of alternating Cu2Cl62- dimers and CuCl2(H2O)2 monomers, with intradimer coupling J1/k=17.35 K and dimer-monomer coupling J2/k=1.93 K. [Copyright &y& Elsevier]

Focuses on a study that reported magnetic results on two new copper (II) chloride salts with emphasis on the relationship between the long copper-chlorine distance and the strength of the interlayer coupling. Details of the experiment; Magnetic and electron paramagnetic resonance results.

The structure of the title compound, (C4H12N)2[CuCl4] or [DEA]2[CuCl4] (DEA is diethylammonium), at 84 (2) K has three crystallographically independent [CuCl4]2− anions in the asymmetric unit, each with a different geometry. These geometries range from essentially square-planar to compressed tetrahedral geometry. The low-temperature structure reported here is the same as the room-temperature structure [Harlow & Simonsen (1976). Am. Crystallogr. Assoc. Ser. 2 Program Abstr. 4, Abstract PBlO], thereby confirming the absence of a low-temperature phase transition. [ABSTRACT FROM AUTHOR]

Abstract: The title compound, Cu(TIM)CuBr4 (where TIM is a macrocycle ligand) is a member of the Cu(TIM)MX4 family, which contains linear chain structures with linkages. This chain structure defines an alternating exchange/alternating site 1d system. For M=Cu, alternating FM/AFM chains are formed with J FM>| J AFM|. Structural and magnetic data are presented, along with an analysis of the exchange pathways. [Copyright &y& Elsevier]

The title compound, [NiCl2(C6H8N2)2], contains centrosymmetric mol­ecules with two phenyl­ene­di­amine ligands coordinated in a bidentate fashion. The Ni-N distances are 2.088 (1) and 2.096 (1) Å, and the Ni-Cl distance of 2.4635 (4) Å. The plane of each phenyl­enedi­amine mol­ecule makes a dihedral angle of 26.53 (7)° with the NiN4 plane. Extensive hydrogen bonding leads to distinct cleavage in the bc plane. [ABSTRACT FROM AUTHOR]

The title compound, (C5H6Br2N3)2[CuBr4], contains isolated substituted pyridinium cations and [CuBr4]2− anions. The di­amino­di­bromo­pyridinium ions are planar, while the CuII ions have a distorted compressed tetrahedral coordination with C2 symmetry. The two independent trans-Br-Cu-Br angles are 128.9 (1) and 136.0 (1)°, with Cu-Br distances of 2.3939 (15) and 2.3790 (16) Å. [ABSTRACT FROM AUTHOR]

In the title compound, 4-(di­methyl­amino)­pyridine is proton­ated on the pyridine N atom. The N(CH3)2 moiety is twisted 4.4 (2)° from the pyridine-ring plane. The octahedral [SnCl6]2− anion is hydrogen bonded via trans-Cl atoms to pyridinium N atoms from two cations forming (C7H11N2)2[SnCl6] structural units. [ABSTRACT FROM AUTHOR]

Abstract: The compounds [2-amino-4,6-dimethylpyridinium]2CuCl4 (1) and [2-amino-4,6-dimethylpyridinium]2CuBr4 (2) were prepared from acidic ethanolic media containing CuX2 and [2-amino-4,6-dimethylpyridine] in the molar ratio 1:1. The compounds were characterized by IR and single-crystal X-ray diffraction and found to be isomorphous in the space group with V =991.2(10)Å3 for (1) and 1059.26(12)Å3 for (2) . There is no significant difference in the non-classical N–H⋯X hydrogen bonding between (1) and (2). The anions show essentially the same extent of distortion from tetrahedral geometry with max./min. values for the X–Cu–X bond angles of 139.72(6)°/96.78(6)° for (1) and 139.43(4)°/96.64(3)° for (2). Each [CuX4]2− anion is hydrogen bonded nonsymmetrically to four cations. In this manner, ladder chains are formed that run along the b-axis, with planar cations falling parallel to the (2,0,1) plane. Weaker π–π interactions exist between cations from different chains with centroid to centroid distance of 4.07Å in (1) and a long 4.594Å in (2). The X–π electrostatic interactions are surprisingly stronger in (2) than in (1) with a Br to centroid of pyridinic ring distance of 3.890Å compared with 3.996Å for the chloride analogue. [Copyright &y& Elsevier]

The crystal structures of the compounds 2,2′-dimethyl-4,4′-biimidazole dihydrate (1) and 2,2′-dimethyl-4,4′-biimidazolium bistrifluoroacetate (2) have been determined. Compound 1 is linked into a three dimensional network via hydrogen bonding between the imidazole nitrogens and the water molecules, while compound 2 forms sheets through hydrogen bonding between the acetate and imidazolium ions. Theoretical calculations for 1 show that the particular prototropic tautomer observed in the crystal structure is not the lowest energy isomer. This observation is justified in terms of hydrogen bonding to the lattice water molecules. [Copyright &y& Elsevier]

The compound (Me4P)2ZnBr4, a member of the β-K2SO4 structure class, undergoes a phase transition at 84°C from the room temperature space group P121/c1 to the parent Pmcn structure. The room temperature structure corresponds to a ferrodistortive transition of B1g symmetry at the zone center. At room temperature, the compound has lattice constants a=9.501(1), b=16.055(2), c=13.127(2) A˚ and β=90.43(1)°. For the high temperature phase, the orthorhombic cell has dimensions a=9.466(2), b=16.351(3) and c=13.284(2) A˚. The structures consist of two crystallographically independent Me4P+ cations and the ZnBr42− anions. In the room temperature phase, all three ionic species show substantial displacement from the mirror plane perpendicular to the a-axis that exists in the high temperature phase, as well as rotations out of that plane. The thermal parameters of the cations are indicative of substantial librational motion. Measurements of lattice parameters have been made at 2–5°C intervals over the temperature range 40–140°C. The changes in the lattice constants appear continuous at Tc (within experimental limits) indicating that the phase transition is likely second-order. The a lattice constant shows an anomalous shortening as Tc is approached. Thermal expansion coefficients are calculated from this data. An application of Landau theory is used to derive the temperature dependencies of spontaneous shear strain and corresponding elastic stiffness constants associated with the primary order parameter. [Copyright &y& Elsevier]

Deals with a study which determined the crystal structure of the copper compound. Chemical components of the copper compound; Measurement of power susceptibilities; Power susceptibility as a function of temperature of the copper analog.

We report on the syntheses, crystal structures, and magnetic susceptibilities of a family of copper pyrazine (pz)-based antiferromagnets with moderate in-plane magnetic exchange. These materials fall into two classes: monoclinic complexes [Cu(pz)2]A2 for A = ClO4 (1) or BF4 (2) and the tetragonal complex [Cu(pz)2(NO3)]PF6 (3). Compound 1 and its deuterated version [Cu(pz-d4)2](ClO4)2 (1a) crystallize in the space group C2/m at room temperature with disordered perchlorate anions. For both 1 and 2, the C centering of the Cu(II), S = 1/2, site yields four equivalent nearest neighbors, producing layers of Cu(II) ions bridged by the pz molecules, which map onto a square magnetic lattice. The layers are offset such that Cu(II) ions lie above and below the holes of adjacent layers. Compound 3 crystallizes in the space group I4/mcm with a layer structure similar to those of 1 and 2 but with Cu(II) ions of adjacent layers stacked above each other and bridged by semicoordinate NO3- ions. The variable-temperature susceptibilities in these compounds approximate a two-dimensional Heisenberg antiferromagnet with J values within the layers of 17.5(3) K (1), 15.3(3) K (2), and 10.8(3) K (3). Ordering transitions are observed in the magnetic data at 4.2(3) and 4,3(5) K for 1 and 2, respectively. [ABSTRACT FROM AUTHOR]

The title compound crystallizes in the monoclinic P2(1)/c space group with a = 11.2470(3) Å, b = 5.9034(2) Å, c = 12.0886(3) Å, β = 115.143(1)°, and V = 726.58(4) Å(3) and consists of discrete monomeric NiCl(2)(o-phenylendiamine)(2) molecules. Each o-phen ligand coordinates in a bidentate mode with the chloride ions occupying trans positions in the resulting tetragonally distorted octahedral coordination sphere. Two discrete sets of N-H···Cl hydrogen bonds link the octahedral molecules into a two-dimensional network, with type 1 interactions linking adjacent monomers along the c axis and type 2 interactions linking monomers along the diagonals in the bc plane. Analysis of the magnetic data reveals the existence of weak antiferromagnetic coupling within the layers via these hydrogen bonds, in addition to the presence of zero field splitting, with the best fit obtained for a 1d antiferromagnetic model with g = 2.0917(7), J/k = -2.11(4) K [J = -1.47(3) cm(-1)], and D = 1.05(3) cm(-1) [β = D/|J| = 0.72(6)] for the model with D > 0 and g = 2.0911(6), J/k = -2.26(1) K [J = -1.57(1) cm(-1)], and D = -0.86(1) cm(-1) [β = D/|J| = 0.55(6)] for the model with D < 0. Theoretical calculations of the exchange coupling confirm the experimental results, yielding values of J(1) = -1.39 cm(-1) for the type 1 hydrogen bonds and J(2)/k = -0.56 cm(-1) for the type 2 hydrogen bonds.

The mixed cation salts, (dimethylammonium)(3,5-dimethylpyridinium)CuX4 (X = Cl, Br), henceforth (DMA)(35DMP)CuX4, are new examples of spin-ladders based on nonbonded halide...halide interactions between CuX4(2-) anions. In these structures, double rows of the CuX4(2-) anions are sheathed by the 35DMP(+) cations, while the edges are capped by the DMA(+) cations. For the Br salt, the Br...Br contacts that define the rungs of the ladder are 4.017 A in length, while those that define the rails are 3.983 A. For the Cl salt, the corresponding lengths are 3.967 and 4.045 A. The susceptibility data for the Br salt exhibits a maximum at approximately 5.5 K, and fitting the data to the spin 1/2 antiferromagnetic ladder model yields 2J(rail)/k = -7.95 K and 2J(rung)/k = -4.07 K. The exchange coupling is much weaker in the Cl salt, no maximum in chi is observed down to 1.8 K, and the corresponding exchange constants are -1.59 and -1.25 K, respectively. An analysis is made of the structural factors involved in the J(rung) pathway.

The synthesis, structure, and magnetic properties of a novel oxalate-based bimetallic magnet obtained by using the chiral (S)-trimethyl-(1-phenyl-ethyl)-ammonium, ((S)-[PhCH(CH3)N(CH3)3](+)), cation as template is reported. This compound can be formulated as [(S)-[PhCH(CH3)N(CH3)3]][Mn(CH3CN)2/3Cr(ox)3] x (CH3CN)&#95;(solvate), and it crystallizes in the chiral trigonal space group P3. It shows a distorted two-dimensional honeycomb structure formed by Mn(II) and Cr(III) ions connected through oxalate anions with [(S)-[PhCH(CH3)N(CH3)3](+) cations and solvent molecules intercalated between the oxalate layers. Two-thirds of the Mn(II) ions of the honeycomb anionic network are heptacoordinated. This compound behaves as a soft ferromagnet with an ordering temperature of 5.6 K.

The crystal structures are reported for two compounds containing novel perforated layer structures, [DBA] 2Cd 9Cl 20.2H 2O and [Cu(TIM)] 2Cu 13Cl 30(H 2O) 2. xH 2O, where [DBA] (+) = di n-butylammonium and TIM = 2,3,9,10-tetramethyl-1,3,8,10-tetraenecyclo- 1,4,8,11-tetraazatetradecane. In the former compound, single Cd (2+) ions are excised from the parent CdCl 2 layers, with water molecules hydrogen bonded to chloride ions on both sides of the excision. Lattice stability is provided by the DBA (+) cations, which have an all-trans conformation. These lie between the layers, hydrogen bonding to the adjacent [Cd 9Cl 20(H 2O) 2] n (2 n- ) sheets. In the copper compound, the modification of the parent CuCl 2 structure is much more complex. In this compound, [Cu 2Cl 2] (2+) moieties are excised in a regular fashion. In addition, at 50% of the Cu1 sites, CuCl 2 species are replaced by pairs of water molecules in a random fashion. The Cu(TIM) (2+) cations bridge the layers via the formation of two semicoordinate bonds to chloride ions at the edge of the [Cu 2Cl 2] (2+) excision sites of adjacent layers.

We report on the syntheses, crystal structures, and magnetic susceptibilities of a family of copper pyrazine (pz)-based antiferromagnets with moderate in-plane magnetic exchange. These materials fall into two classes: monoclinic complexes [Cu(pz)2]A2 for A = ClO4 (1) or BF4 (2) and the tetragonal complex [Cu(pz)2(NO3)]PF6 (3). Compound 1 and its deuterated version [Cu(pz-d4)2](ClO4)2 (1a) crystallize in the space group C2/m at room temperature with disordered perchlorate anions. For both 1 and 2, the C centering of the Cu(II), S = 1/2, site yields four equivalent nearest neighbors, producing layers of Cu(II) ions bridged by the pz molecules, which map onto a square magnetic lattice. The layers are offset such that Cu(II) ions lie above and below the holes of adjacent layers. Compound 3 crystallizes in the space group I4/mcm with a layer structure similar to those of 1 and 2 but with Cu(II) ions of adjacent layers stacked above each other and bridged by semicoordinate NO3- ions. The variable-temperature susceptibilities in these compounds approximate a two-dimensional Heisenberg antiferromagnet with J values within the layers of 17.5(3) K (1), 15.3(3) K (2), and 10.8(3) K (3). Ordering transitions are observed in the magnetic data at 4.2(3) and 4.3(5) K for 1 and 2, respectively.

Two types of halogen...halide synthons are investigated on the basis of theoretical and crystallographic studies; the simple halogen...halide synthons and the charge assisted halogen...halide synthons. The former interactions were investigated theoretically (ab initio) by studying the energy of interaction of a halide anion with a halocarbon species as a function of Y...X- separation distance and the C-Y...X- angle in a series of complexes (R-Y...X-, R=methyl, phenyl, acetyl or pyridyl; Y=F, Cl, Br, or I; X-=F-, Cl-, Br-, or I-). The theoretical study of the latter interaction type was investigated in only one system, the [(4BP)Cl]2 dimer, (4BP=4-bromopyrdinium cation). Crystal structure determinations, to complement the latter theoretical calculations, were performed on 13 n-chloropyridinium and n-bromopyridinium halide salts (n=2-4). The theoretical and crystallographic studies indicate that these interactions are controlled by electrostatics and are characterized by linear C-Y...X- angles and separation distances less than the sum of van der Waals radius (rvdW) of the halogen atom and the ionic radii of the halide anion. The strength of these contacts from calculations varies from weak or absent, e.g., H3C-Cl...I-, to very strong, e.g., HCC-I...F- (energy of interaction ca. -153 kJ/mol). The strengths of these contacts are influenced by four factors: (a) the type of the halide anion; (b) the type of the halogen atom; (c) the hybridization of the ipso carbon; (d) the nature of the functional groups. The calculations also show that charge assisted halogen...halide synthons have a comparable strength to simple halogen...halide synthons. The nature of these contacts is explained on the basis of an electrostatic model.

A study of the halogen...halogen contacts in organic compounds using ab initio calculations and the results of previously reported crystallographic studies show that these interactions are controlled by electrostatics. These contacts can be represented by the geometric parameters of the C--X1...X2--C moieties (where theta1=C--X1...X2 and theta2=X1...X2--C; ri=X1...X2 distance). The distributions of the contacts within the sum of van der Waals radii (rvdW) versus thetai (theta1=theta2) show a maximum at theta approximately 150 degrees for X=Cl, Br, and I. This maximum is not seen in the distribution of F...F contacts. These results are in good agreement with our ab initio calculations. The theoretical results show that the position of the maximum depends on three factors: 1) The type of halogen atom, 2) the hybridization of the ipso carbon atom, and 3) the nature of the other atoms that are bonded to the ipso carbon atom apart from the halogen atom. Calculations show that the strength of these contacts decreases in the following order: I...I>Br...Br>Cl...Cl. Their relative strengths decrease as a function of the hybridization of the ipso carbon atom in the following order: sp2>sp>sp3. Attaching an electronegative atom to the carbon atom strengthens the halogen...halogen contacts. An electrostatic model is proposed based on two assumptions: 1) The presence of a positive electrostatic end cap on the halogen atom (except for fluorine) and 2) the electronic charge is anisotropically distributed around the halogen atom.

Catena(dimethylammonium-bis(mu2-chloro)-chlorocuprate), (CH3)2NH2CuCl3, forms chains of Cu2Cl6(2-) bifold dimers linked along the structural chain axis by terminal chlorides forming long semicoordinate bonds to adjacent dimers. The structural chains are separated by dimethylammonium ions that hydrogen bond to chloride ions of the dimers. A structural phase transition below room temperature removes disorder in the hydrogen bonding, leaving adjacent dimers along the chain structurally and magnetically inequivalent, with alternating ferromagnetic and antiferromagnetic pairs. The coupled dimers are magnetically isolated from each other along the structural chain axis by the long semicoordinate Cu-Cl bond. However, the dimers couple to like counterparts on adjacent chains via nonbonding Cl...Cl contacts. The result is two independent magnetic chains, one an alternating antiferromagnetic chain and the other an antiferromagnetic chain of ferromagnetically coupled copper dimers, which run perpendicular to the structural chains. This magnetostructural analysis is used to fit unusual low-temperature (1.6 K) magnetization vs field data that display a two-step saturation. The structural phase transition is identified with neutron scattering and capacitance measurements, and the X-ray crystal structures are determined at room temperature and 84 K. The results appear to resolve long-standing confusion about the origins of the magnetic behavior of this compound and provide a compelling example of the importance of two-halide magnetic exchange.

The crystal structure consists of a strongly hydrogen bonded network of tris(N-ethylammonium)ammonium cations, Cu3Cl12(6)- trimeric species, and Cl- anions. The Cu3Cl12(6)- trimers are formed by two distorted tetrahedral CuCl4(2)- anions linked to a central square planar CuCl4(2)- anion via semicoordinate Cu-Cl...Cu mu1 bridges. The central copper ion shows only small deviations from ideal D4h symmetry, while the terminal copper ions show a mild distortion from D2d symmetry with an average trans Cl-Cu-Cl angle of 136.0 degrees. The semicoordinate linkages provide a ferromagnetic exchange pathway between the copper ions with J/k = 6.91(3) K. Short Cl...Cl contacts (3.67-3.90 angstoms) lead to very weak antiferromagnetic coupling between the ferromagnetically coupled trimers., (Copyright 2004 American Chemical Society)

The crystal structure of bis(cyclopentylammonium)tetrabromocuprate(II) has been determined at room temperature and at -70 degrees C. The room temperature structure is orthorhombic, space group Pn2(1)a, with a = 12.092(6) A, b = 8.134(4) A, and c = 18.698(10) A. The low temperature structure is also orthorhombic, space group Pna2(1), with a = 24.111(5) A, b = 8.089(2) A, and c = 18.448(4) A. DSC studies reveal the presence of a weak endotherm at -13 degrees C. The structures of the two phases are very similar, differing only in the relative orientations of the cyclopentyl rings of the organic cations and slight displacements of the anionic tetrahedra. The CuBr(4)(2)(-) anions in the low temperature phase are arranged to define a spin ladder system through Cu-Br.Br-Cu two-halide exchange pathways. Magnetic susceptibility data have been analyzed and yield antiferromagnetic exchange strengths 2J(rail)/k = -11.6 K and 2J(rung)/k = -5.5 K with a singlet-triplet gap energy Delta/k(B) = 2.3 K. This is the first report of a spin ladder with a stronger interaction along the axis of the ladder than along the rungs.

Synthesis of azide complexes with the copper(II) macrocycle complex Cu(14ane)(2+) (where 14ane = 1,4,8,11-tetraazacyclothetradecane) has yielded two compounds. Cu(14ane)Cu(N(3))(4) contains micro(1,3)-azido bridged chains of Cu(14ane)(2+) cations and Cu(N(3))(4)(2)(-) anions. Magnetic studies reveal the presence of ferromagnetic interactions within the chains with J/k = 0.635(4) K. [Cu(14ane)N(3)]BF(4) contains [Cu(14ane)N(3)]+ cations with elongated square pyramidal geometry. The BF(4)(-) anions are weakly coordinated in the sixth coordination site of the cations.

The structures of three hybrid organic/inorganic halometalate salts are reported, and the layer structures developed are contrasted. Crystal structures of the isostructural N-methylethylenediammonium (MEDA(2+)) and N-ethylethylenediammonium (EEDA(2+)) salts of copper(I) bromide are both triclinic, space group P1, with lattice constants a = 6.284(7), b = 7.842(6), and c = 12.03(1) A, alpha = 84.84(3), beta = 83.08(2), and gamma = 88.00(3) degrees, and V = 586(1) A(3) with Z = 2 for (MEDA)Cu(2)Br(4) while (EEDA)Cu(2)Br(4) has lattice constants a = 6.27(2), b = 7.78(2), and c = 13.12(3) A, alpha = 84.69(4), beta = 78.18(3), and gamma = 88.17(7) degrees, and V = 623(3) A(3) with Z = 2. The dominant inorganic feature in both salts is anionic (CuBr(2))(n)(n-) chains of edge-shared CuBr(4) tetrahedra. The diammonium cations hydrogen bond these chains together into a unique double layer structure. For comparison purposes, the crystal structure of (CHA)PbBr(3) (CHA(+) = cyclohexylammonium) is reported (monoclinic, space group P2(1)/n, a = 8.088(2) A, b = 7.912(2) A, and c = 19.572(4) A, beta = 96.98(4) degrees, and V = 1243.2(4) A(3) with Z = 4). This contains (PbBr(3))(n)(n-) halometalate chains, this time of face-shared PbBr(6) octahedra. However, here the organic cations tie the chains together into the more common single layer structure.

The compounds (C(6)N(2)H(10))CuX(4), where the cation is diprotonated 3-picolylamine and X = Cl(-) or Br(-), form an unusual variant of the normal antiferrodistortive A(2)CuX(4) lattice [(C(6)N(2)H(10))CuCl(4), orthorhombic, Pna2(1), a= 7.747(1), b = 24.960(2), and c = 17.041(1) Å, Z = 12; (C(6)N(2)H(10))CuBr(4), orthorhombic, Pna2(1), a = 8.133(1), b= 26.129(1), and c = 17.148(1) Å, Z = 12]. The structures contain ribbons of the antiferrodistortive sheets which are six copper atoms wide. The central four Cu(II) ions have the usual elongated octahedral coordination, while on each edge are CuX(4)(2)(-) ions which have a distorted tetrahedral geometry. Long Cu.X interactions (4.000 and 4.124 Å for the Cl and Br salts, respectively) between these terminating anions link the ribbons together into sheets. The organic cations provide overall stability to the lattice and link adjacent sheets together, forcing the existence of short two-halide X.X contacts between sheets (average Cl.Cl = 4.629 Å, Br.Br = 4.425 Å). While the changes in the semicoordinate Cu.X distances upon replacement of Cl by Br mirror the change in ionic radius, the X.X distances actually decrease when the larger bromide ion is introduced. This is because these distances are largely dictated by the size of the organic cation. The magnetic data for both salts show the presence of predominant ferromagnetic interactions at high temperature. The Cl salt orders antiferromagnetically at T(c) = 5.7 K, and the susceptibility data can be fit to a S = (1)/(2) Heisenberg model for antiferromagnetically coupled ferromagnetic layers with a mean in-plane exchange constant of J/k = 8.13 K and an interlayer exchange constant of J'/k = 1.22 K. The corresponding values for the Br salt are T(c) = 18.9 K, J/k = 21.3 K, and J'/k = 5.87 K The increase in magnitude of the exchange constants and ordering temperature of the Br salt relative to the Cl salt is consistent with the increase in ionic radius of Br(-) relative to Cl(-).

The compound (dabcoH(2))(2)Cl(3)[CuCl(3)(H(2)O)(2)].H(2)O, where dabco = 1,4-diazabicyclo[2.2.2]octane, has been synthesized, its structure has been determined by single-crystal structural analysis, and its properties have been investigated by powder and single-crystal EPR spectroscopy. The compound crystallizes in space group Pnma at room temperature with unit cell dimensions of a = 15.227(1) Å, b = 7.467(1) Å, and c = 20.166(2) Å with Z = 4. The structure was solved by the Patterson method and refined by full-matrix least-squares to R = 4.3% for 1681 observed reflections (I > 2sigma(I)). The [CuCl(3)(H(2)O)(2)](-) anion exists with a slightly distorted trigonal bipyramidal geometry in which the three Cl atoms lie in equatorial positions and the two water molecules are in axial positions. The distortion appears to be driven by the presence of N-H.Cl hydrogen bonds. The EPR spectra are also consistent with the presence of only a small distortion from trigonal bipyramidal geometry since g(1) approximately g(2) > g(3) approximately 2.0. Analysis of the geometry indicates the distortion consists primarily of a "negative" C(2)(v)() type. Analysis of the thermal parameters supports the supposition that the observed geometry corresponds to disorder over two "positive" C(2)(v)() distortions.