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Uranium(vi) trans-bis(imido) complexes [U(κ4-{(tBu2ArO)2Me2-cyclam})(NPh)(NPhR)] react with CO2 to eliminate phenyl isocyanates and afford uranium(vi) trans-[O[double bond, length as m-dash]U[double bond, length as m-dash]NR]2+ complexes, including [U(κ4-{(tBu2ArO)2Me2-cyclam})(NPh)(O)] that was crystallographically characterized. DFT studies indicate that the reaction proceeds by endergonic formation of a cycloaddition intermediate; the secondary reaction to form a dioxo uranyl complex is both thermodynamically and kinetically hindered.

Uranium(vi) trans-bis(imido) complexes [U(κ4-{(tBu2ArO)2Me2-cyclam})(NPh)(NPhR)] react with CO2 to eliminate phenyl isocyanates and afford uranium(vi) trans-[O[double bond, length as m-dash]U[double bond, length as m-dash]NR]2+ complexes, including [U(κ4-{(tBu2ArO)2Me2-cyclam})(NPh)(O)] that was crystallographically characterized. DFT studies indicate that the reaction proceeds by endergonic formation of a cycloaddition intermediate; the secondary reaction to form a dioxo uranyl complex is both thermodynamically and kinetically hindered.

New iron and cobalt bis(dithiolene) complexes [M(3cbdt)2] (3cbdt = 3-cyanobenzene-1,2-dithiolate) were prepared as tetraphenylphosphonium (Ph4P+) salts for Fe in the monoanionic state and for Co in both the dianionic and monoanionic states: (Ph4P)2[Fe(III)(3cbdt)2]2 (1); (Ph4P)2[Co(III)(3cbdt)2]2 (2); (Ph4P)2[Co(II)(3cbdt)2] (3). These compounds were characterized by single-crystal X-ray diffraction, cyclic voltammetry, EPR, and static magnetic susceptibility. Their properties are discussed in comparison with the corresponding complexes based on the isomer ligand 4-cyanobenzene-1,2-dithiolate (4cbdt) and 4,5-cyanobenzene-1,2-dithiolate (dcbdt), previously described by us. The Fe(III) and the Co(III) compounds (1 and 2) are isostructural, crystallizing in the triclinic P 1 ¯ space group, with cis [M(III)(3cbdt)2] complexes dimerized in a trans fashion, and the transition metal (M = Fe, Co) has a distorted 4+1 square pyramidal coordination geometry. The Co(II) compound (3) crystallizes in the triclinic P 1 ¯ space group, with the unit cell containing one cis and three trans inequivalent [Co(II)(3cbdt)2] complexes with the transition metal (Co) and having a square planar coordination geometry. The Fe(III) complex (1) is EPR-silent, and the static magnetic susceptibility shows a temperature dependence typical of dimers of antiferromagnetically coupled S = 3/2 spins with −J/kB = 233.6 K and g = 1.8. Static magnetic susceptibility measurements of compound (3) show that this Co(II) complex is paramagnetic, corresponding to an S = ½ state with g = 2, in agreement with EPR spectra showing in solid state a hyperfine structure typical of the I(59Co) = 7/2. Static susceptibility measurements of Co(III) complex (2) showed an increase in the paramagnetic susceptibility upon warming above 100 K, which is consistent with strong AFM coupling between dimerized S = 1 units with a constant −J/kB ~1286 K. [ABSTRACT FROM AUTHOR]

New nickel and copper bisdithiolene complexes were prepared as tetraphenylphosphonium (Ph4P+) salts, (Ph4P)n[M(3cbdt)2], [n = 1, 2; M = Ni, Cu; 3cbdt = 3-cyanobenzene-1,2-dithiolate]: (Ph4P)2[Ni(3cbdt)2] (1); Ph4P[Ni(3cbdt)2] (2); (Ph4P)2[Cu(3cbdt)2] (3); Ph4P[Cu(3cbdt)2] (4), and characterised by single crystal X-ray diffraction, cyclic voltammetry, EPR and static magnetic susceptibility for the paramagnetic species. These Cu and Ni complexes obtained as stable monoanionic and dianionic anions are the first members of this family of cyano benzene functionalized bisdithiolene transition metal complexes, opening the way to the preparation of analogous compounds with other transition metals and their future use as building blocks for the preparation of molecular materials. Their properties are discussed in comparison with the corresponding complexes based on the 4-cyanobenzene-1,2-dithiolate (4cbdt) ligand previously described by us. The salts (Ph4P)n[M(3cbdt)2], [n = 1, 2; M = Ni, Cu] present the metal complexes always in a square-planar coordination geometry with a ligand trans configuration, but revealing a rich polymorphism. The Ni and Cu compounds are isostructural and occur as two polymorphs (α, β) with the exception of the salt of the monoanionic Ni complex, that was found only as the α-polymorph. The salt of the dianionic Ni complex was found to crystallise also with one acetonitrile molecule, when recrystallised from this solvent. The salts of monoanionic [Ni(3cbdt)2] and dianionic [Cu(3cbdt)2] complexes have been characterised by EPR and static magnetic susceptibility as paramagnetic S = 1/2 species. [ABSTRACT FROM AUTHOR]

Five new salts of 5-cyanobenzene-ethylenedithio-tetrathiafulvalene (CNB-EDT-TTF), with the general formula (CNB-EDT-TTF)4A, and anions A = Ag(CN)2 (1), Ag(CN)2·H2O (2), Ag2(CN)3 (3), Ag(SCN)2 (4) and Hg2(SCN)5 (5), were prepared by electrocrystallisation and characterised by single crystal X-ray diffraction, electrical conductivity, thermoelectric power and magnetic susceptibility measurements. Their crystal structure is based on a double layer arrangement of the donors with a β′′ packing pattern identical to that previously observed in related salts with small discrete anions. The donor bilayers are separated by layers of anions which however are incoherently arranged perpendicular to the layers. The average structures obtained are compatible with anionic arrangements similar to those previously observed in single layer salts of BEDT-TTF and related donors, where, with the exception of 1, the anions are polymeric. While 2 presents electrical resistivity with a thermally activated regime, 1, 3, 4 and 5 show metallic behaviour at high temperatures, with room temperature values in the range 10–20 S cm−1 and sample dependent electronic localisation effects at lower temperatures. The thermoelectric power of these compounds is +82–90 μV K−1 at room temperature, following behavior identical to that of their analogues with small discrete anions. The paramagnetic susceptibility of 4 and 5, similar to those of their analogues with I3, PF6, AsF6 and ReO4 anions, has values of ≈1.0 × 10−3 emu mol−1 at room temperature, being significantly enhanced compared with the Pauli-type contribution predicted from electron band calculations. [ABSTRACT FROM AUTHOR]

The crystal engineering strategy have revealed crucial factors for the synthesis of the first stacked dianionic Ni(super III) dimeric compound with a Ni2Se8 coordination environment, each Ni center showing a square-pyramidal geometry. A metal-centered Ni(super II)/Ni(super III) redox process is proposed to occur, which is clearly reflected in the geometry change that accompanies the alteration of the Ni center oxidation state.

The importance of C–H⋯N≡C interactions in the crystal engineering of conducting materials was recently evidenced by a new type of two-dimensional conducting material with the composition of (5-CNB-EDT-TTF)4A with a variety of anions A, where CNB-EDT-TTF denotes the electron donor cyanobenzene-ethylenedithio-tetrathiafulvalene, which has been described in the last few years, presenting a new type of bilayer structure. The unique bilayer donor structure of these compounds is due to the network of C–H⋯N≡C interactions, which although generally considered weak, are effective in the self-assembly of the crystal structure. The role of these weak interactions is made clear by a comparison of the salts of this donor and the related isomer 4-CNB-EDT-TTF, where no bilayer structure is obtained but a variety of related interactions are observed instead. This comparison allows different patterns of weak C–H⋯N≡C interactions to be identified in these compounds, which can be described as combinations of several different synthons of type R 22 (10), R 22 (24), R 22 (26), R 23 (10), R 24 (8), R 24 (10), R 48 (20), and R 34 (30) or C(5) and C(6) infinite chains. The different patterns of interactions are comparable with those observed in other cyano compounds, as well as the magnitude of the interaction enthalpy associated with the different synthons, as estimated by means of density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]