Iridium electronic structure

Ir Me3tpa)(ethene)] + have indicated that MeCN coordination to the metal can be sufficient to overcome the unfavorable bending of the olefin, thus yielding an iridium-olefin species with an electronic structure intermediate between a slipped olefin Ir —CH2=CH2 and an alkyl radical Ir —CH2—CH2 description (see Section IV.D). In addition to the energy gain from MeCN coordination, delocalization of the unpaired spin to iridium renders formation of such species less unfavorable in this case. 

The period under discussion has seen intense interest in the recently discovered i7 -H2 complexes. The relevance of these to some isomerization reactions of square-planar complexes was reported in Volume 5 of this series, and is covered in another recent review. " More of these fluxional ds-dihydridoplatinum compounds have been reported, and the role of 17 -H2 derivatives in oxidative additions to d rhodium(I) and iridium(I) has been discussed. The increasing role of theoretical and bonding studies is reflected in four works relevant to 4-and 5-coordinate molecules. Electronic structure is related to chemical reactivity in the reactions of phosphine bases with d bis(l,l-dithiolato)platinum com-plexes. Huckel calculations on the reactions of bis(nitrogen donor) ligands with 16-electron platinum(II) complexes have been carried out, as has more work on symmetry selection rules for isomerization reactions, which includes pseudorotation of 5-coordinate complexes and square-planar to tetrahedral conversions of 4-coordinate molecules. ... 

In a number of papers attempts have been made to find a correlation between the catalytic activity and physicochemical characteristics of metals and alloys. It has been suggested that the strong catalytic properties of platinum— ruthenium alloys can be related to their electronic structure [247, 248]. The number of impaired d electrons on the catalyst atom can serve as a quantitative characteristic of the electronic structure. According to [247], for platinum and palladium the number of d electrons on the atoms is 0.6 for rhodium 1.4 for iridium 1.7 and for ruthenium 2.2. 

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