Homoleptic dithiolenes structural properties

To underpin the syntheses, properties, and applications of dithiolene molecules, this chapter presents a comprehensive discussion of structurally characterized homoleptic dithiolene complexes. That is, the structural unit must contain dithiolene ligands as the only ligand type, and there must be only one type of dithiolene ligand. Emphasis is placed on structural aspects such as coordination geometries, bond distances and angles, and on identifying trends related to the specific dithiolene ligand and the identity and formal oxidation... 

A great amount of research has focused on the electronic structure, spectroscopy, redox properties, and conductivity of homoleptic bis(l,2-dithiolene) complexes of c transition metal ions (51). The compounds are often highly... 

Some homoleptic unsymmetrical (dmit/mnt, dmit/tdas) dithiolene nickel complex-based D-A compounds with D = TTF and EDT-TTF also exhibit metal-like conductivity (see Table I) (101). Their molecular structure is shown in Scheme 3. The unsymmetrical tetraalkylammonium salts [MLjLJ- (M = Ni, Pd, Pt) have been prepared by ligand exchange reaction between tetraalkylammonium salts of MLj and ML21 (128, 129) and the D-A compounds have been synthesized by electrooxidation. Among these complexes, only the Ni derivatives exhibit metallic-like properties, namely, TTF[Ni(dmit)(mnt)] (metallic down to --30 K), a-EDT-TTF[Ni(dmit)(mnt)] (metallic down to 30 K), TTF[Ni(dmit)(tdas)] (metallic down to 4.2 K), and EDT-TTF[Ni(dmit)(tdas)] (metallic down to --50 K) (see Table I). The complex ot-EDT-TTF-[Ni(dmit)(mnt)J is isostructural (130) to a-EDT-TTF[Ni(dmit)2)] [ambient pressure superconductor, Section II.B.2 (124)]. Under pressure, conductivity measurements up to 18 kbar show a monotonous decrease of the resistivity but do not reveal any superconducting transition (101). 

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