J. Sala Pala

RADICAL CATION-RADICAL ANION SALTS : MOLYBDENUM COMPLEXES CONTAINING THE TCNQ.- OR TCNE.- RADICAL ANIONS. X-RAY CRYSTAL STRUCTURE OF MO(ET2NCS2)4(TCNQ )

Abstract The reactions between the molybdenum(IV) complexes [Mo(dtc) 4 ] 1 (dtc = Et 2 NCS 2 for 1a and Me 2 NCS 2 for 1b ) and TCNQ produced the 1 : 1 derivatives [Mo(dtc) 4 ](TCNQ) 2. Subsequent reaction of 2 with TCNQ gave the 1 : 2 complexes 3 [Mo(dtc) 4 ](TCNQ) 2 . Complexes 1 reacted with TCNE under nitrogen to give the 1 : 1 compounds [Mo(dtc) 4 ](TCNE) 4 while under ambient conditions the pentacyanopropenide derivatives [Mo(dtc) 4 ](NC) 2 CC(CN)C(CN) 2 ] 5 were obtained. In solution, cyclic voltammetry and ESR studies revealed the presence for all types of complexes of the molybdenum(V) radical cation [Mo(dtc) 4 ] •− which is associated with the radical anion TCNX •− in 2 (X = Q) and 4 (X = E) and with a 1:1 mixture of neutral and anionic TCNQ species in 3 . Complex 2a has been studied by single crystal X-ray diffraction. The crystal structure consists of monomeric TCNQ •− radical anions and [Mo(dtc) 4 ] •+ cations with a triangular dodecahedral arrangement of S atoms and a point group symmetry which is approximately D 2 d .

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 .

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.

Preparation, X-ray crystal structure and theoretical study of the bonding in [Mo2O4I2L3] (L = OPPh3), an example of an unsymmetrical dinuclear molybdenum complex

Abstract The reaction between the oxomolybdenum(V) complex Et4N[MoOI4(H2O)] and triphenylphosphine oxide (L = OPPh3) produces the mononuclear complex [MoOI3L2] and the dinuclear complex 1 [Mo2O4I2L3], the crystal structure of which has been studied by X-ray. Each metal centre is bound to a terminal and two bridging oxygen atoms; the Mo2O2 central fragment appears slightly disymmetric with a short MoMo distance [2.557(1) A], in agreement with a single metalmetal bond. The whole structure is strongly asymmetric, with the three phosphorus ligands bound to a first molybdenum atom with a distorted octahedral MoO6 coordination and the two iodo ligands bound to a second molybdenum atom which has a cis-MoOO2I2 square-pyramidal coordination. Extended Huckel calculations on the model [Mo2O4I2L3] (L = OPH3), the structure of which was derived from the averaged structure of 1, have been performed to understand the structure and bonding in this unsymmetrical dimer. They show a HOMO-LUMO gap of 1.06 eV and indicate that 1 can be considered unambiguously as an MoVMoV [and not an MoIVMoVI] dinuclear complex. An orbital explanation is provided to rationalize why the cis conformation is generally preferred for MoVMoV dinuclear species: such a conformation allows a stronger MoMo bond. Some predictions are made, concerning the reactivity of the MoMo bond with respect to nucleophilic and electrophilic attacks.