Roger D. Willett

Thermochromic phase transitions in transition metal salts

g!) Dichloro[ trans-2-(2’-quinolyl)methylene-3-quinuclidinone]~ckel(II) ..... 127 Dibromo( trans-2-(2’-quinolyl)methylene-3-quinuc~dinone]~ckel(II) ..... 133 (iii) Dichloro[ trans-2-(6’-methoxy-2’-quinolyl)methylene-3quinuclidinone]nickel(II) 133 (iv) Dichloro[bis(3,5-dimethylpyrazolyl)methane]nickel(II) 133 (v) Dichloro(2,9-dimethy1-1,1O-phenanthroline)nickel(II) 134 (vi) summary 135 C. Thermochromic compounds containing N, N-diethylethylenediamine 135

The crystal structure of (C2H5NH3)2CuCl4

Abstract The structure of the complex salt (C2H5NH3)2CuCl4 has been determined by conventional X-ray diffraction techniques. The space group is Pbca with lattice constants a = 21.18 A b = 7.47 A, and c = 7.35 A. A square planar CuCl42− ion was found with CuCl distances of 2.28 A. The coordination sphere about each copper atom is completed by sharing additional chlorine atoms from adjacent CuCl42− ions yielding two CuCl distance of 2.98 A. This ties the CuCl42− groups into a two-dimensional framework lying in the yz plane. The nitrogen atom is located in a « hole » formed by the chlorine atoms in this framework. Several short NCl distances are found which are presumably associated with hydrogen bonds. The ethyl groups are disordered in this structure.

Crystal Structure of (NH4)2CuCl4

The crystal structure of the yellow compound (NH4)2CuCl4 has been determined by x‐ray diffraction studies. The compound crystallizes in the orthorhombic space group Cmca with a=15.46 A, b=7.20 A, and c=7.20 A. The structure contains discrete, planar CuCl4= ions with Cu–Cl distances of 2.30 and 2.33 A. These ions are then bonded together by longer Cu–Cl bonds of 2.79 A to form infinite two‐dimensional sheets. The yellow compounds (CH3NH3)2CuCl4 and (C2H5NH3)2CuCl4 probably have closely related structures.

Electron spin resonance spectra and covalent bonding in the square‐planar CuCl42− and CuBr42− ions

Electron paramagnetic resonance spectra of copper‐doped potassium tetrachloropalladate and potassium tetrabromopalladate have been observed. Both hyperfine and superhyperfine structures are resolved at room temperature. The CuCl42− and CuBr42− units are in a square‐planar configuration. The data can be fitted with an axial spin Hamiltonian. The parameters are as follows; g∥ = 2.232, g⊥=2.049, A∥Cu=163.6 × 10−4cm−1, A⊥Cu=34.5 × 10−4cm−1, A∥Cl=23.3 × 10−4cm−1, and A⊥Cl=5.3 × 10−4cm−1 for CuCl42− and g∥ = 2.143, g⊥=2.0438, A∥Cu=189.5 × 10−4cm−1, A⊥Cu=45.8 ×−4cm−1, A∥Br=123 × 10−4cm−1, and A⊥Br=27.9 × 10−4cm−1 for CuBr42−. The MO parameters are evaluated exactly. There are strong covalent in‐plane σ and π bonds and out‐of‐plane π bonds. The covalency is larger for Br− than Cl− as a ligand. Data were also obtained on single crystal copper‐doped tetraphenylarsonium trichloropalladate. The pure salt contains Pd2Cl62− dimers, and the EPR spectra are consistent with PdCuCl62− dimeric units in the doped species. Th...

Spectral nature, antifungal activity and molecular structure of metal complexes of acetylpyrazine 4N-substituted thiosemicarbazones

SummaryNickel(II) and copper(II) complexes of acetylpyrazine 3-azabicyclo[3.2.2]-nonylthiosemicarbazone and nickel(II) complexes of acetylpyrazine 4N-methyl-, 4N-dimethyl-, and 3-hexamethyleneiminylthiosemicarbazone have been synthesized and characterized by their spectral and physical properties. Crystal structures for the nickel(II) complexes of the 4N-methyl- and 4N-dimethyl-derivatives, with a chloro ligand in the fourth coordination position, are included. The growth inhibition by the four thiosemicarbazones and their metal complexes against two human pathogenic fungi, Aspergillus niger and Paecilomyces variotii, have been evaluated.

The crystal structure of copper(II) chloride bis(dimethylsulphoxide)

Abstract [(CH 3 ) 2 CuCl 2 belongs to the orthorhombic system, Pnma, with 4 formula groups in a unit cell. The dimensions of the unit cell at 23–24°C are a = 8.0542±0.00013, b = 11.5464±0.0105, c = 11.3670±0.0082A. The calculated density of 1.827 g/cc agrees well with the measured value of 1.83 g/cc. Intensities of 1609 independent reflections were measured by counter using θ–2θ can technique. Refinement of atomic parameters including hydrogen positional parameters has led to a R of 0.075. The crystal structure was determined by the heavy-atom method. It consists of a distorted square planar coordination for copper in which the Cl(1)CuCl(2) angle is 146.13±0.09° and the four bond lengths are: 2.283±0.003A for CuCl(1), 2.290±0.002A for CuCl(2), and 1.955±0.004 A for the two equivalent CuO bonds.

Synthesis, X-ray structures and magnetic properties of linear chain 4-cyanopyridine compounds: [Cu(4-CNpy)4(H2O)](ClO4)2 and M(4-CNpy)2Cl2 (M Mn, Fe, Co, Ni, Cu)

Abstract The synthesis, structures and magnetic properties of linear chain complexes of metal ions with 4-cyanopyridine are reported (4-CNpy=4-cyanopyridine): [Cu(4-CNpy) 4 (H 2 O)](ClO 4 ) 2 and M(4-CNpy) 2 Cl 2 (MMn, Fe, Co, Ni, Cu). All compounds crystallize in monoclinic systems. Crystallographic data for [Cu(4-CNpy) 4 (H 2 O)](ClO 4 ) 2 ] n ( 1 ): space group P 2 1 / c with a = 13.225(3), b = 10.567(2), c = 20.522(3) A , β = 99.71(2)°, V = 2826.7(9) A 3 , Z = 4, D calc = 1.640 Mg m −3 , μ = 3.430 mm −1 . The compound contains primer CuL 4 units with the ligands bounded to copper ions through the ring nitrogens. These units are weakly linked into chains through semi-coordinated bonds between the nitrile nitrogen and an adjacent copper ion via the axial sites. The magnetic data show only a weak antiferromagnetic interaction ( θ CW = −0.52(1) K). Crystallographic data for [Cu(4-CNpy) 2 Cl 2 ] n ( 2 ): space group P 2 1 / n with a = 3.779(2), b = 25.711(12), c = 7.104(4) A , β = 95.98(4)°, V = 686.48(4) A 3 , Z = 2, D calc = 1.658 Mg m −3 , μ = 5.575 mm −1 . Crystallographic data for [Mn(4-CNpy) 2 Cl 2 ] n ( 6 ): space group P 2 1 / c with a = 3.700(2), b = 7.198(2), c = 26.520(5) A , β = 92.13(3)°, V = 705.8(4) A 3 , Z = 2, D calc = 1.572 Mg m −3 , μ = 1.303 mm −1 . Both dichloride compounds similar structures, consisting of chains of metal ions bibridged by chlorides with the 4-CNpy ligands coordinated to the metal ions in the axial sites through the pyridine nitrogens. The difference in space groups is caused by the different modes of packing the chains into 3D lattices. Infrared spectra and powder X-ray diffraction patterns indicate that the remaining compounds form an isostructural series. The powder magnetic susceptibilities have been measured between 2 and 300 K for all compounds. Antiferromagnetic exchange (Cu, Mn) or ferromagnetic exchange (Ni, Co, Fe) exists within the chains. The Ni, Co and Fe compounds order antiferromagnetically at 7.2(2), 2.1(2) and 4.6(2) K, respectively. Magnetic field induced transitions have been observed in these three compounds below their ordering temperatures. The copper and manganese data have been fit to models for Heisenberg antiferromagnetic linear chain with S = 1 2 and S = 5 2 with exchange constants J Co / k = −13.7(2) K and J Mn / k = −0.5 7(1) K, respectively. The nickel and cobalt data have been fit to models for ferromagnetic linear chains, with the nickel compound corresponding to a S = 1 Heisenberg model with exchange constant J / lk = +4.8(2) K, and the cobalt compound to a S = 1 2 ferromagnetic Ising linear chain with exchange constant J / k = + 6.6(2) K. The iron data has not been successfully to fit to any model. It is concluded that the total magnetic interaction between the chains has been increased by approximately 50% by the substitution of 4-CNpy for pyridine.

Crystal Structure and Optical Properties of (CH3)2NH2CuCl3

The crystal structure of (CH3)2NH2CuCl3 has been determined by x‐ray diffraction techniques. The compound contains approximately planar Cu2Cl6= dimers which contain two bridging chlorine atoms. All Cu–Cl bond distances in the dimer are approximately 2.3 A and all bond angles approximately 90°. The crystals are pleochroic with maximum visible absorption when the electric vector is parallel to the [301] direction.

Crystal chemistry of the copper bromide/2-aminopyrimidine system

Abstract The preparation and crystal structures are reported for seven compounds obtained from the interaction of copper(II) bromide with 2-aminopyrimidine. This includes four copper(II) bromide compounds and three copper(I) bromide complexes. The L = 2-aminopyrimidine moiety can exist as neutral L species, as well as either a monoprotonated LH + cation or a diprotonated LH 2 2+ dictation in which one or two of the ring nitrogen atoms, respectively, are protonated. The neutral ligand is found to coordinate to one or two Cu ions through the ring nitrogen atoms, while the monocation may or may not coordinate through the unprotonated ring nitrogen atom. The crystals are stabilized by hydrogen bonding between the halide ions and the −NH 2 and/or > N  H + fragments. The Cu(II) species show a range of coordination geometries L 2 CuBr 2 contains isolated four-coordinate species with a planar coordination geometry ( CuN = 1.996(5) and CuBr = 2.401(1) A ) (LH) 2 CuBr 4 contains isolated six-coordinate species with a square planar CuBr 4 2− arrangement ( CuBr = 2.427(1) and 2.487(1) A ) augmented by two LH ligands ( CuN = 2.787(6) A ). The (LH) 2 Cu 2 Br 6 salt contains planar bibridged Cu 2 Br 6 2− dimers (CuBr(av.) = 2.424 A) which aggregate into stacks through the formation of semicoordinate CuBr bonds ( distances = 3.067(1) and 3.335(1) A ). Finally, (LH) 2 CuBr 4 contains isolated distorted tetrahedral CuBr 4 2− anions, with CuBr = 2.388 A (av.) and the larger trans BrCuBr angles of 135.4° (av.). The Cu(I) compounds all contain a common structural element: a (CuBr) n chain as illustrated in I with CuBr ≌ 2.52−2.56 A and CuBrCu = 99–107°. In each chain, the Cu(I) ion completes a tetrahedral coordination by forming bonds to Br − ions or ring N atoms in the ligands. In LCuBr, the pyrimidine ligands bridge Cu atoms on adjacent chains, forming a rectangular two dimensional network. This gives the Cu(I) ion a N 2 Br 2 coordination environment. For the LCu 2 Br 2 compound, the (CuBr) n chains dimerize through the formation of CuBr linkages between chains. The pyrimidine ligands now bridge between Cu atoms on adjacent dimerized chains. Thus the Cu(I) ion has a Br 3 N coordination environment. Finally, in (LH)CuBr 2 , each copper ion in the chain completes its coordination sphere by coordinating to one pyridinium cation and to one bromide ion, to also attain a Br 3 N coordination sphere.

The crystal structure of bis(isopropylammonium)tetrachlorocuprate(II)

Abstract The structure of the low temperature (green) phase of the thermochromic compound bis(isopropylammonium)tetrachlorocuprate(II), [CH3)2CHNH3]2CuCl4, has been determined by X-ray diffraction. The compound crystallizes in the triclinic space group P1 with lattice constants of a = 7.245(1) A, b = 14.588(1) A, c = 21.738(1) A, α = 87.08(1)°, β = 103.59(1)° and γ = 104.73(1)° at 20°C. There are six formula units per unit cell. Least squares refinement of 3240 reflections with I >2σ1 led to a final value of R = 7.3%. The structure contains discrete CuCl42− ions which pack together to form infinite ribbons parallel to the a-axis. The ribbons are held together by hydrogen bonds between the CuCl42− ions and the isopropylammonium ions. One-third of the CuCl42− ions have a square-planar geometry; the other two-thirds have a small tetrahedral distortion superimposed on the square- planar configuration.