Dithiolenes different dithiolene ligands

We are therefore faced here with radical complexes which easily distort depending on the structural arrangement and whose SOMO is different for every crystal structure associated with a given counter-ion, a very original feature in these series. The unfolded d1 complexes can be described as Mo(IV) complexes with a spin density essentially localized on the dithiolene ligand while the more folded complexes have a stronger metal character. This variable spin density delocalization is expected to influence strongly the amplitude and dimensionality of intermolecular interactions between radical species in the solid state, as detailed below in Sect. 3. 

Multifunctional dithiolene ligands have been used to prepare binuclear as well as polymeric complexes. Some examples of this type of complex were already mentioned above (25 and 41) and involve the ligands benzenetetrathiol (51) or its alkyl ethers,78 the tetrathiosquaric acid (52), ethylenetetrathiol (53) and tetrathiooxalic acid (54) and its Se analog. The two-electron difference in oxidation state between (53) and (54) is much the same as that discussed for the parent dithiolene ligand. Crystallographic results (see Section 16.5.3.1) point out the equivalence of the latter two ligands. 

Dithiolenes can serve quite well as bridging ligands (see compound 43). A regular dithiolene ligand has also been shown to coexist in a binuclear complex with a bridging one the sulfur rich dithiolene28 Mo2(S2)(S2C2Ph2)4, cited earlier in a different context, is an example of this type of coexistence. 

The ability of the dithiolene ligand to promote in-plane spin delocalization in metallo-bis(dithiolenes) has been determined using [Cu(mnt)2]2, which possesses an unpaired electron in an in-plane b g (d ) orbital (390). This electronic structure allows a detailed comparison with the out-of-plane 7t-type spin delocalization present in square-planar nickel bis(dithiolenes). Interestingly, the measured spin delocalization onto the dithiolene ligands in [Cu(mnt)2]2 is remarkably different from that determined for [Ni(mnt)2]1-and [Ni(tds)2]1. The ESEEM studies on the [Cu(mnt)2]2 ion doped in a diamagnetic [Ni(mnt)2]2 host have determined that 50% of the unpaired spin... 

Several intriguing differences were observed between the oxidized and reduced/sulfurated forms of aldehyde oxidase (18). First, there is a significantly different distance between the dithiolene sulfur atoms, 3.0 A in the oxidized form as compared to 3.5 A in the reduced form. The short S—S separation has been interpreted as a partial bond, whose precedent exists in Mo bis(thiolato) complexes (80, 81). The importance of a partial disulfide resides in the possibility of dithiolene ligand-based redox that accompanies turnover or otherwise occurs in these enzymes. The longer bonds in the reduced form seem to effect a puckering of the M0S2C2 ring of the dithiolene chelate. 

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