Transition metals 1.2- dithiolene complexes

The 0/1 couple in Au(tfd)21 (tfd = bis(trifluoromethyl)ethylenedithiolate, lb) occurs at a slightly lower potential (+1.32 V vs SCE in CH2CI2) than the mnt counterpart911. This is in accord with observations that in other transition metal 1,2-dithiolene complexes the ease of oxidation is dependent on X with X = Ph > CF3 > CN9. Replacing sulfur with the less electronegative atom, selenium, results in a lower oxidation potential for Aul lds)2 (tds = bis(trifluoromethyl)ethylenediselenolate, lc) relative to [Au( ltd) 12. More electronegative substituents make a complex easier to reduce, as expected. Thus, the 1/2 couple for Au(mnt)2 occurs approximately 500 mV more positive than the same couple for [Au(tds)2]. ... 

Similar processes are observed with transition metal dithiolene complexes, in which a range of formal oxidation states of metal ions may be accommodated. In reality, this is... 

This chapter discusses the synthesis of transition metal dithiolene complexes and is current to late 2002. Dithiolene chemistry has been reviewed several times previously, but this is the first review dedicated to synthetic aspects. Emphasis is placed on more contemporary methods, and the reader should consult the older reviews, especially those by Mueller-Westerhoff et al. (8) and McCleverty (9) for discussions of earlier literature. An effort was made to be comprehensive with respect to methods and the range of complexes examined, but the chemistry of metal dithiolenes is so vast that it is not practical to be exhaustive. 

Transition metal dithiolene complexes have received considerable attention since their discovery in 1962 because of their unusual optical, magnetic, electronic, and electrochemical properties (170, 294, 370). Dithiolene ligands, 26 (R = H, Me, Ph, CN, CF3 R = H, Me, etc.) have been shown to stabilize unusual formal oxidation states (294) and geometries (133), for example, Rh, and the trigonal prismatic geometry in Re(S2C2H2)s. 

Mdssbauer spectra of bonding and structure in, 15 184-187 reactions with diborane, 16 213 stabilization of, 5 17, 18-19 cyanates, 17 297, 298 cyanide complexes of, 8 143-144 cyclometallated bipyridine complex, 30 76 diazene complexes, 27 231-232 dinitrogen complexes, 27 215, 217 diphosphine complexes of, 14 208-219 dithiocarbamates, 23 253-254 -1,2-dithiolene complexes, 22 323-327 hydrogen bonding, 22 327 halide complexes with phosphine, etc., 6 25 hexaflouride, structure, 27 104 hydride complexes, 20 235, 248-281, see also Transition metal-hydride complexes... 

Chapter 2- Transition metal dithiolenes are versatile complexes eapable of a wide range of oxidation states, coordination geometries, and magnetie moments. As a eonsequence, these complexes have been widely studied as building bloeks for erystalline molecttlar materials. Particularly successful are the square-planar metal dithiolenes (Chart 1), from which materials have been produeed that exhibit condueting, magnetic, and nonlinear optieal properties, as well as supereonduetivity in some cases. " In their application to molecular- based... 

Most of the compounds listed in this class (Table 7) are tetraalkylammonium (R4N+) salts of metal dithiolene complexes. These salts generally exist in a 2 1 or 1 1 stoichiometry. The 2 1 salts, such as [ra-Bu4N]2[Cu(mnt)2]114) and [Et4N]2-[Cu(mnt)2]115,116) can exhibit interesting properties, but they will not be considered here since the transition-metal components are isolated from each other (d(M-M) > 5 A). 

As has been noted previously81, the structural parameters of metal dithiolene complexes are relatively insensitive to the overall charge on the complex, and the monoanionic dithiolene complexes generally retain the mmm (D2h) molecular symmetry found in both neutral and dianionic dithiolene complexes. The only notable structural trend is a lengthening of the M-S bond as the overall charge on the transition-metal complex increases. 

Last, but not least, Chapter 11 reveals how the dithiolene unit has been used as a building block to construct more complex organic ligands. These ligands form a remarkable variety of novel complexes (see dedication) that display new forms of reactivity, which may yet reveal ways in which important small molecules are activated and converted by enzyme systems in the transition metal dithiolene family. 

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