Iridium complexes 2,2 -bipyridyl

The preparation of bis(bipyridyl) (702) and bis(phenanthroline) cobalt(III) complexes (576) has been the subject of a number of papers. Interest centers on the possibility of cis-trans isomerism in these complexes, since it would seem that the close approach of the 6,6 -(bipyridyl) and 2,9-(phenanthroline) protons in the trans complex would make this stereochemistry unattractive for central ions such as co-balt(III), rhodium(III), or iridium(III). Cis complexes are well established, but a violet compound claimed to be anionic cobalt(II) species (21, 573, 591). 

The structure of a further iridium bis(boryl) complex, the cationic species [(tbbpy)(cod)Ir(Bpin)2]+[OTf] (9.33), together with that of a related neutral tris(boryl) system (vide infra), has been reported as part of a study to elucidate the mechanism and intermediates of arene borylation chemistry [136]. 9.33 features an approximately octahedral coordination geometry with mutually cis pairs of bipyridyl, diene and Bpin ligands. The two Ir-B bond lengths [2.06(2) and 2.12(1) A] are effectively identical within the standard 3a limit. 

Apart from the phosphine complexes described, the hydrogen transfer activity of several other derivatives has also been investigated. Among them rhodium, and iridium bipyridyl, and phenanthroline compounds displayed the highest catalytic activity with turnover numbers up to 900 cycles/min. Reducing unsaturated ketones, first the C=C double bond is saturated, but the successive reduction of the C=0 group is comparable in rate with that of the olefinic bond. 

Bipyridyl complexes of Ru(II) can be used for the production and storage of multiple photochemical redox equivalents by attachment to a soluble polymer. The photoactive complexes have been bound to a styrene/chloromethylstyrene copolymer by nucleophilic displacement of the chloro groups from the chloromethyl-styrene. Because the excited state properties are relatively unaffected in the mixed-valence polymers, it is possible to build up a chain of approximately 30 oxidative equivalents with a (bpy)2Ru or a (bpy)20s moiety bonded to each strand of the polyma . Excited state donors and acceptors can also be immobilized using a sol-gel technique. Such a technique has been s plied to the 1,4-dimethoxyl-benzene mediated photoinduced electron transfer between bipyridyl complexes of ruthenium and iridium. Metallopolymeric films have also been used for energy... 

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