S. Triki

Molecular assemblies based on tricyanomethanide units and copper(II) ions

Abstract New co-ordination polymers of formulae [Cu(tcm) 2 (tn)] ( 1 ) and [Cu(tcm)(tn) 2 ](tcm) ( 2 ) (tcm − =tricyanomethanide and tn=1,3-diaminopropane) have been synthesised and characterised by X-ray crystallography and magnetic measurements. For compound 1 , the Cu(II) ion presents an elongated and distorted CuN 4 N 1 N 1 octahedron generated by one chelating tn ligand and by four μ 2 -bridging tcm − ligands. The molecular arrangement of 1 can be described as a monodimensional chain of a ladder-like structure in which the Cu⋯Cu distance (7.5157(4) A) through the tcm − ligand forming the sides is significantly shorter than the corresponding distance observed through that providing the rung (7.7455(4) A). For compound 2 , the Cu(II) ion presents a centrosymmetric elongated CuN 4 N 2 octahedron; the equatorial plane is generated by two chelating tn ligands and the two axial positions are filled by two weakly co-ordinated equivalent tcm − units acting as μ 2 -bridging ligands. This leads to a monodimensional polymer in which the intrachain Cu⋯Cu distance is 9.1062(2) A. Magnetic measurements, performed in the temperature range 2–300 K for both compounds, show weak antiferromagnetic interactions for compound 1 while compound 2 obeys a Curie law. The difference between the magnetic behaviours can be explained from the larger intrachain Cu⋯Cu separation in 2 than in 1 .

Polymeric networks of copper(II) ions linked by a bridging polynitrile ligand

Synthesis, crystal structure and magnetic properties of [Cu{C[C(CN) 2 ] 3 }(en) 2 ] n , which arises from reaction of Cu(II) with the highly conjugated polynitrile C 10 N 6 2 ligand ( C 10 N 6 2 = [C{C(CN) 2 } 3 ] 2. ) in presence of ethylenediamine (an = NH 2 CH 2 CH 2 NH 2 ). are reported. This compound presents a polymeric structure of pseudo-octahedral copper(II) ions bridged by the polynitrile unit C 10 N 6 2 . The magnetic susceptibility data in the 5-300 K range can be analysed by a Curie law with C = 0.43 cm 3 . K.mol -1 .

Pentacyanopropenide group as ligand in organometallic chemistry. Crystal structure and electrochemical studies of (Et4N)[W(CO)5{(C(CN)2C(CN)C(CN)2}]

Abstract The title complex has been obtained by reaction of the tetraethylammonium pentacyanopropenide with tungsten hexacarbonyl in acetone. Its crystal structure involves discrete [W(CO)5{C3(CN)5}]− anions in which the organic fragment is N-coordinated via one of the nitrogen atoms of a cyano group borne by one of the terminal carbon atoms of the allylic skeleton. The anion presents a distorted octahedral coordination with a W–N bond length [2.168(5) A] considerably longer than the W–C bond lengths [cis-W–C in the range 1.998(7)–2.068(4) A; trans-W–C 1.962(7) A]. Cyclic voltammograms of this complex, recorded in CH2Cl2 and CH3CN (Bu4NPF6 0.1 M), display a quasi-reversible reduction and irreversible oxidation waves.

Synthesis and characterisation of new binuclear oxo-vanadium(IV) complexes with a bis(bidentate)oxalate bridge. Crystal structures of the cationic and anionic complexes [V2O2(C2O4)(H2O)6]Cl2·4Bu4NCl·H2O and [FeCp*2]2[Et4N]2[V2O2(C2O4)(NCS)6]

Abstract The new oxalate–vanadyl compounds [V2O2(C2O4)(H2O)6]Cl2·4Bu4NCl·H2O (1) (Bu=C4H9) and [Et4N]4[V2O2(C2O4)(NCS)6] (2′) (Et=C2H5) have been synthesized starting from V2O5 and VOSO4·5H2O, respectively. Metathesis of 2′ with [FeCp*2]BF4 (Cp*=C5(CH3)5) gave a partial substitution of the cations affording [FeCp*2]2[Et4N]2[V2O2(C2O4)(NCS)6] (2). The X-ray structures of 1 and 2 have been determined. In both complexes, which crystallise in the monoclinic space group P21/c, the centrosymmetric binuclear vanadium species present a bis(bidentate)oxalate ligand and an almost planar [V2O2(C2O4)X2] unit (X=O(H2O) for 1 and N(NCS) for 2) with two VO groups located in trans positions in the equatorial plane. In both cases, the strong VO terminal bond (1.569(7) in 1, 1.580(7) A in 2) has a strong trans influence which is slightly greater in the cation of 1 than in the anion of 2. Magnetic susceptibility measurements indicate weak antiferromagnetic pairwise interactions for 1, 2 and 2′.

Radical cation salts based on BEDT-TTF and the paramagnetic anion [Cr(NCS)6]3-

Abstract A new radical cation salt formulated as (ET)5.5[Cr(NCS)6] (ET = BEDT-TTF = bis(ethylene)dithiotetrathiafulvalene) has been synthesised and characterised by X-ray diffraction and magnetic measurements. The structure shows the presence of alternating layers of the ET units and mixed layers of anions and an isolated ET molecule. The magnetic susceptibility data in the temperature range 2–300 K show a Curie law with C = 1.771 cm3.K.mol−1 and Nα = 1.20.10−5 cm3.mol−1, in agreement with the presence of isolated Cr(III) without any contribution from the organic part.