Homoleptic dithiolenes

Beswick, Colin L., Structures and Structural Trends in Homoleptic Dithiolene... 

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... 

Similar to homoleptic dithiolene complexes, alkylation of Cp2M(S2C2Z2) results in the alkyl group being added to the ligand sulfur atom (Eq. 28) (131). 

Homoleptic dithiolene complexes such as ML , where L = dithiolene ligand (1,1-, 1,2- or 1,3-), and n = 2 [bis(dithiolene)] or 3 [tris(dithio-lene)] (see Scheme 2). Within this class of compounds, a further distinction should be made between symmetrical compounds in which all dithiolene ligands are identical [see, e.g., M(mnt)2 in Scheme 3 ... 

Although several authors have reported on symmetrical and unsymmetrical homoleptic dithiolene complexes for third-order NLO applications (368, 436-440), the most complete and significant studies have been carried out by Underhill and co-workers (397, 431, 433, 434, 441-448). Two of these systems are shown in Scheme 25. One of the conclusions (434) is that an optimized material should absorb 800 nm (433) in order to have the highest ratio x(3 /a. For obtaining the material in a useful form, it is also proposed to embed the dithiolene complexes as guests in polymers such as poly(methylmethacrylate) (PMMA) (434, 449, 450). Along this line, the most efficient material in this series is the bis[l-butyl-2-phenylethene-l,2-dithiolato(2 )-S,S ]nickel(II) compound (29) shown in Scheme 25 (451). 

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