Joost P. Cornelissen

Preparation, spectroscopic and magnetic characterization of a new series of two-dimensional transition metal compounds. The x-ray structure of poly-bis(thiocyanato-N)-bis-μ- [1,2,4] triazolo [1,5-a] pyrimidine-N1,N3)iron(II)

The synthesis of a series of polynuclear compounds of general formula [M(tp) 2 (NCS) 2 ] n (M = Mn, Fe, Co, Ni and tp = [1,2,4]triazolo[1,5− a ]pyrimidine, C 5 H 4 N 4 ) is described. The compounds are X-ray and IR isostructural and were further characterized by ligand field and magnetic susceptibility measurements. The structure of the iron compound was determined by X-ray diffraction methods. It crystallizes in the orthorhombic space group Aba 2, with a =8.028(2), b =20.422(6), c =10.129(5) A. The structure has been solved from diffractometer data by Patterson and Fourier methods and refined by full-matrtx least-squares to R = 0.040 for 706 observed reflections. The structure consists of octahedral iron complexes in which the metal atom is coordinated by two nitrogen atoms from two monodentate NCS groups and by four nitrogen atoms from four symmetry-related tp molecules; each organic ligand bridges two metal atoms through both non-bridgehead triazole nitrogen atoms, joining the octahedral complexes in a layered system where the Fe···Fe distance is 6.49 A.

Structures and properties of bis(thiocyanato-N)bis(6-methyl[1,2,4]triazolo[1,a]pyrimidine-N3)copper(II), a distorted tetrahedral copper(II) thiocyanate compound, and bis(thiocyanato-N)bis(5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-N3)copper(II), a polynuclear pseudo-layered system

The molecular structures and spectroscopic properties of the compounds [Cu(NCS)2(L)2] (L = 6-methyl[1,2,4]triazolo[1,5-a]pyrimidine, C6N4H6, abbreviated 6mtp, and L = 5-methyl[1,2,4]triazolo[1,5-a]pyridimine, C6N4H6, abbreviated 5mtp) are described. The structures of [Cu(NCS)2(6mtp)2] (1) and [Cu(NCS)2(5mtp)2] (2) have been determined by single-crystal X-ray diffraction. Compound 1 is monoclinic, space group C2/c, with a = 12.096(9), b = 8.466(6), c = 18.327(7) A, β = 101.95(9)°, Z = 4. Compound 2 is monoclinic, space group P21/c, with a = 12.451(7), b = 8.952(5), c = 8.061(5) A, β = 106.53(2)°, Z = 2. Both structures have been solved from diffractometer data by Patterson and difference Fourier methods, and refined by full-matrix least-squares to R = 0.0365 for 1400 observed reflections (1) and to R = 0.0370 for 1195 independent observed reflections (2). In 1 mononuclear complexes are present, in which each copper atom is surrounded by four donor nitrogen atoms: two N-atoms of two N(3)-coordinating 6mtp ligands, and two N-atoms of the non-bridging NCS-ions in a distorted tetrahedral arrangement (CuN = 1.931(3)–1.975(2) A, NCuN = 93.5(1)–143.5(1)°). In 2 four donor nitrogen atoms, from two N(3)-coordinating 5mtp ligands and two monodentate NCS-ions, give square-planar copper in a trans configuration (CuN = 1.921(4)–2.020(4) A, NCuN = 91.2(1)-88.8(2)°). Two N(1)-atoms of the 5mtp ligands of neighbouring complexes, at a rather long distance of 2.677 A, complete the elongated octahedral coordination of the metal and join the complexes in layers.

Crystal structure and electrical conductivity of N-methylquinolinium bis(1,3-dithiole-2-thione-4,5-dithiolato)nickelate(III)

Abstract The crystal structure and electrical conductivity of [MeQ][Ni(dmit)2] is reported (dmit = 1,3-dithia-2-thione-4,5-dithiolate and MeQ = N-methylquinolinium). The compound crystallises in the monoclinic space group P21/n, with a = 17.55(1), b = 10.893(7), c = 23.11(2) A, β = 92.30(9)° and Z = 4 with the asymmetrical unit having formula Ni2C32H20N2S20. The structure was solved by direct methods, Fourier and least-squares techniques. It consists of diads made up from two crystallographically independent Ni(dmit)2 units, and two N-methylquinolinium cations lying next to the [Ni(dmit)2]2 diads. Both Ni(dmit)2 units show considerable deviation from planarity, i.e. a distortion towards a V shape and a twist towards a more tetrahedral environment around the nickel atoms. The Ni(1)S distances vary from 2.142(5)–2.167(5) A, and the Ni(18)S bond lengths are between 2.157(5)–2.2162(5) A. The overall packing motive can be considered as being highly irregular. In the crystal lattice several short interdiad S…S contacts are present, the shortest one being 3.491(7) A, building a two-dimensional network. In accordance, with its structure and its stoichiometry, the compound behaves as a semiconductor with a relatively high room-temperature conductivity of 10−3 S cm−1.

Preparation, spectroscopic and magnetic characterization of two pseudo layered copper(II) systems. The x-ray structures of bis(thiocyanato-N)bis([1,2,4] triazolo[1,5-a]pyrimidine-N3)copper(II) and dichlorobis([1,2,4]triazolo[1,5-a]pyrimidine-N3)copper(II)

Abstract The structures of α-Cu(NCS)2(tp)2 (1) and CuCl2(tp)2 (2), with tp = [1,2,4]triazolo[1,5-α]pyrimidine, C5H4N4, have been determined by single crystal X-ray diffraction methods. 1 is monoclinic, space group P21/c, with a = 11.669(2), b = 8.808(2), c = 7.951(2) A, β = 102.52(2)° and Z = 2. 2 is also monoclinic, space group P1/c, with a = 9.546(1), b = 8.958(1), c = 8.082(1) A, β = 107.32(1)° and Z = 2. Both compounds show essentially layered structures with the copper atoms square planarly coordinated by two nitrogen atoms (trans) from N3-coordinating tp ligands and by two donor atoms (trans) from anions [N atoms from thiocyanate ligand in 1 and Cl atoms from chloride ligands in 2; in 1 CuN (tp ligand) = 2.035(5) and CuN(thiocyanate group) = 1.935(6) A, in 2 CuN(tp ligand) = 2.021(4) and CuCl = 2.297(1) A]; the coordination is completed to octahedral by two nitrogen atoms from adjacent tp molecules which N1-coordinate axially to the metals at relatively long distances (CuN = 2.633(6) in 1 and 2.692(4) A in 2) so that in both compounds two-dimensional systems parallel to each other are formed. The structural properties of the two compounds are correlated to their IR, UV and ESR spectra and magnetic susceptibilities.

Crystal structures and electrochemical properties of two phases of tetrabutylammonium bis(1,3-dithiole-2-thione-4,5-diselenolato)nickelate(III)

Abstract The crystal structures of two phases (α and β) of [Bu4N]2[Ni(dsit)2]2 are reported (dsit=1,3-dithiole-2-thione- 4,5-selenolate). The compound crystallises either in blocks (α-phase) or needles (β-phase). The α-phase crystallises in the triclinic space group P 1 , with a=12.381(3), b=14.009(2), c=9.571(1) A, α=94.43(1), β=99.61(2), γ=81.32(2)° and Z=1 with the asymmetric unit having the formula Ni2C44H72N2S12Se8. The β-phase crystallises in the triclinic space group P 1 , with a=11.820(1), b=14.998(1), c=9.517(1) A, α=96.980(8), β=100.251(9), γ=76.926(8)° and Z=1 with the asymmetric unit having the formula Ni2C44H72N2S12Se8. The structures were solved by direct methods, and refined by Fourier and least-squares techniques. Both crystal structures differ only marginally. They consist of anionic dimers made up of two chemically bound Ni(dsit)2 units. The Ni atom is square pyramidally coordinated by five selenium donor atoms, with the apically bridging NiSe distances (2.48 and 2.47 A for α- [Bu4N]2[Ni(dsit)2]2 and β-[Bu4N]2[Ni(dsit)2]2, respectively) being significantly longer than the equatorial distances (2.316–2.347 A). In the β-phase one of the thionyl groups and three of the four butyl chains of the cations are in disorder. Because of the bulky nature of the cations, no short interdimer contacts are present in the lattices. Cyclic voltammety studies of [Bu4N]2[Ni(dsit)2]2 in acetone show a first reversible 2[Ni(dsit)2]−⇌[Ni(dsit)2]22− couple at E1/2=−0.12 V (versus Ag/AgCl), and a second quasi-reversible couple involving a single anodic peak at 0.18 V and two reduction peaks at 0.08 and −0.01 V.

Crystal and molecular structure of diaquabis(thiocyanato-N)bis(5-methyl-[1,2,4]triazolo[1,5-a]pyridine-N3)cobalt(II), [Co(NCS)2(C6H6N4)2(H2O)2]

The X-ray crystal structure of the title compound, [Co(NCS)2(C6H6N4)2(H2O)2], has been determined. The crystals are monoclinic, space groupC2/c, with cell dimensionsa=15.6901(5),b=7.9248(10),c=16.1278(12) Å,β=94.4(8)°Vc=1999.44 Å3,Mr=479.18,Z=4,Dx=1.5918 Mg m3,Cu Kα radiation (graphite crystal monochromator, λ=1.54051 Å), μ(CuKα)=39.08 cm−1,F(000)=980.00 andT=290 K. Final conventionalR-factor=0.051, andRw=0.053 for 1430 “observed” reflections and 141 variables. The structure was solved using the programsPatsys andDirdif. The Co atom is octahedrally coordinated (CoN2O2N2 chromophore), with only the 5-methyl-[1,2,4]-triazolo[1,5-a]pyrimidine (5mtp) ligands in thetrans positions. The triazolo pyrimidine rings are planar and coordinated through their N(3) atoms. The H2O ligands are also H-bond donors to N(4) (intramolecularly) and to the S atoms of the NSC anions (intermolecularly).

Crystal structures, electrical conductivity and band-structure calculations of three new [cation][Ni(C3S5)2]2 compounds

The mixed-valence radical salts [smdt][Ni(C3S5)2]21, [dmp][Ni(C3S5)2]22 and [dmm][Ni(C3S5)2]23(C3S52–= 1,3-dithiole-2-thione-4,5-dithiolate, smdt =S-methyl-1,3-dithianium, dmp =N,N-dimethylpyrrolidinium and dmm =N,N-dimethylmorpholinium) have been obtained by electrochemical oxidation of the corresponding [cation][Ni(C3S5)2] complexes in acetonitrile. Single-crystal X-ray studies revealed that all three crystallise in essentially the same packing mode. Their structure consists of anionic diads stacked face-to-face along one direction. The stacks form layers of Ni(C3S5)2 units which are separated by the cations. In the structure of 3 two types of Ni(C3S5)2 layers exist, exhibiting different structural and electrical properties. The acceptor molecules neighbouring along the longest axis make an angle of 135 (1), 139 (2) and 152°(3) with each other, thereby forming a herringbone motif. In all three structures, short intermolecular S ⋯ S contacts can be found predominantly between Ni(C3S5)2 units lying side-by-side to each other, but also within the stacks in 3. At ambient pressure, all three Ni(C3S5)2 compounds have room-temperature conductivities ranging between 1 and 70 S cm–1. Their thermal behaviour is consistent with semiconductors having activation energies of about 0.14 eV. Band-structure calculations were carried out and found to be in agreement with the observed conductivities when some degree of electron correlation is taken into account. Calculation of molecular orbital overlaps indicated dimerisation of the anions, with a weak, essentially two-dimensional conduction pathway for salts 1 and 2. In the crystal lattice of 3 one Ni(C3S5)2 layer can be considered as conducting along the stacking direction, while in the second type of layer a two-dimensional conduction pathway appears to be present.

Conducting Ni(DMIT)2-compounds with a new class of closed-shell cations. Conductivity and crystal structures of [SMDT][Ni(DMIT)2]2 and [DMP][Ni(DMIT)2]2

Abstract Small, cyclic, saturated cations form a new class of closed shell counter cations to be used in combination with radical anions such as Ni(dmit) 2 n− (dmit 2− = 4,5-dimercapto-1,3-dithia-2-thione). The crystal structures of [smdt][Ni(dmit) 2 ] 2 ( I ) smdt = S - methyl -1,3- dithianium ) and [dmp][Ni(dmit) 2 ] 2 ( II ) ( dmp = N,N - dimethylpyrrolinium ) , the first inorganic conductors based upon this type of cations, were determined. In both compounds the anionic units stack in a herring-bone motive. Short interstack sulfur-sulfur contacts are found along two dimensions, but there is no significant overlap between the orbitals of the thionyl groups. Both compounds are semi -conductors. Their room temperature conductivity is 1–10 ohm −1 cm −1 and E a = 0.15 eV.

Synthesis, crystal structure and electrical properties of two new palladium complexes of selenium and sulfur ligands: [NMe4][Pd(C3S3Se2)2]2 and [PMe4][Pd(C3S5)2]2

The compounds [NMe4][Pd(C3S3Se2)2]2 and [PMe4][Pd(C3S5)2]2[C3S3Se2= 4,5-bis(hydroseleno)-1,3-dithiole-2-thionate; C3S5= 4,5-dimercapto-1,3-dithiole-2-thionate] have been prepared by electrochemical oxidation of [NBu4]2[Pd(C3S3Se2)2] and [NBu4][Pd(C3S5)2] in the presence of a large excess of NMe4PF6 and PMe4I, respectively. Their structures have been determined by X-ray crystallographic methods. Both compounds, with space group C2/c, are isostructural to the superconducting phase β-[NMe4][Pd(C3S5)2]2. The PdL2(L = C3S3Se2 or C3S5) entities are paired, forming [(PdL2)2] dimmers with a Pd–Pd bond length of 3.174 and 3.177 A, respectively. The structure consists of [(PdL2)2] dimer layers in the (001) plane separated from each other by sheets of cations. The dimers are stacked along [110] and [10]. Both compounds show similar electrical properties: the room-temperature conductivities are ≈ 50 and ≈ 20 S cm–1, respectively; at high temperature the conductivity is weakly temperature dependent, but abruptly decreases at low temperatures; the conductivity increases when applying pressure. A broad dispersion of optical excitations was observed in the reflectance spectra of [NMe4][Pd(C3S3Se2)2]2, indicating an overlap of the highest occupied (HOMO) and lowest unoccupied molecular orbital (LUMO) bands and a HOMO-type conduction band.