Other nitrogen donor ligands

Several papers have appeared concerning Ru -porphyrin complexes. The first examples of metalloporphyrin dimers linked by M—M bonds have been synthesized  

Taube s recent isolation of a pyrazine-bridged Ru -Ru dimer 

Although Taube s pyrazine Ru —Ru dimer was produced by the Ag oxidation of [(NHjljRu—NC4H4N—Ru(NH3)5] , attempts to prepare similar Ru -Ru complexes from [(NH3)5Ru(C5H4N)2Ru(NH3)5] and [(NHjljRu—NC5H4C2H4C5H4N—Ru(NH3)5] were unsuccessful. Cyclic voltammetric data indicated a two-electron oxidation to Ru -Ru dimers. In view of the identical ligands around each Ru atom, Mayoh and Day have questioned the localization of the Ru valencies in Taube s dimer into discrete Ru and Ru centres. However, a theoretical calculation of the conditions necessary for valence trapping in any mixed valence system, showed that the condition is indeed satisfied by the above Ru compound. Other workers have suggested that the available data on this complex could also be explained by a molecular orbital scheme in which the Ru ion and pyrazine-filled n (or k ) molecular orbitals are mixed, and the unpaired electron is mainly but un-symmetrically shared by the two cations.  

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Other nitrogen donor ligands. A series of complexes of the unusual 1,3-di-p-tolyltriazenido ligand (L) (9) has been prepared, including [OsH(CO)-(PPh3)2L]. The i.r. spectrum of the diamagnetic, air-stable complex indicates bidentate co-ordination of... 

In common with other nitrogen donor ligands, the majority of reported coordination compounds are with later d transition elements, or early B subgroup elements, in oxidation states of II or III. Tetraaza macrocycles predominate, with 14 followed by 16 as the most common ring sizes. 

Other nitrogen donor ligand complexes reported include some 67... 

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