Stabilization of Isolated Mixed-Valence Trimers in a Novel Nickel Dithiolene Complex with CF2 Substituents

Olivier J. Dautel (1) , Marc Fourmigué (1)

1 IMN - Institut des Matériaux Jean Rouxel

The preparation of the novel paramagnetic nickel dithiolene complex Ni(F2pdt)2- (F2pdt2-: 2,2-difluoro-1,3-propanediyldithioethylene-1,2-dithiolate) and its X-ray crystal structure as n-Bu4N+ salt are described. (n-Bu4N)[Ni(F2pdt)2] (2) crystallizes in the orthorhombic system, space group Pna21 with a = 21.379(4) Å, b = 8.9702(18) Å, and c = 18.527(4) Å. The radical anions are isolated from each other by the bulky n-Bu4N+ cations and exhibit a Curie-type magnetic behavior. Two reversible redox waves corresponding to the redox couples Ni(F2pdt)22-/- and Ni(F2pdt)2-/0 are observed at -0.55 and 0.30 V vs SCE, illustrating the electron withdrawing effect of the CF2 substituents. As a consequence, (TTF)3(BF4)2 oxidation of the radical anion does not afford the neutral Ni(F2pdt)20 but a TTF salt formulated as [TTF]3[Ni(F2pdt)2]3[CH2Cl2]. It crystallizes in the triclinic system, space group P with a = 12.330(3) Å, b = 12.726(3) Å, c =15.706(3) Å, = 91.10(3), = 110.78(3), and = 116.01(3). Donor and acceptor moieties are organized into (TTF)32+ and [Ni(F2pdt)2]32- trimers whose dicationic and dianionic charges have been inferred from the intramolecular bond lengths evolution and the singlet-triplet magnetic behavior. These trimers arrange orthogonally to each other into chess-board-like slabs, characterized by a segregation of the CF2 fragments and further stabilized by weak C-H···F interactions. Extended Hückel calculations show that only the nickel dithiolene complex trimer actually contributes to the magnetic susceptibility.

Domaines: Chimie organique; Matériaux; Cristallographie

Olivier J. Dautel, Marc Fourmigué. Stabilization of Isolated Mixed-Valence Trimers in a Novel Nickel Dithiolene Complex with CF2 Substituents. Inorganic Chemistry, 2001, 40 (9), pp.2083 - 2087. ⟨10.1021/ic0013835⟩. ⟨hal-00177994⟩