Homoleptic complexes ruthenium

For this triad, only iron (Table 4.17) gives homoleptic complexes containing (tM — C bonds. The remaining elements form heteroleptic compounds. The stability of phosphine complexes of the type M(aryl)2 (PR3)2 decreases considerably according to the series Ni>Co>Fe. Ruthenium and osmium complexes characteristically activate the C —H bond in coordinated ligands and form compounds with (tM—C bonds as a result of oxidative addition. The following reactions serve as examples ... 

Osmium forms a wide variety of alkyl and aryl complexes including homoleptic alkyl and aryl complexes and many complexes with ancillary carbonyl (see Carbonyl Complexes of the Transition Metals), cyclopentadienyl (see Cyclopenta-dienyl), arene (see Arene Complexes), and alkene ligands (see Alkene Complexes). It forms stronger bonds to carbon and other ligands than do the lighter elements of the triad. Because of this, most reactions of alkyl and aryl osmium complexes are slower than the reactions of the corresponding ruthenium complexes. However, because osmium is more stable in higher oxidation states, the oxidative addition (see Oxidative Addition) of C-H bonds is favored for osmium complexes. The rate of oxidative addition reactions decreases in the order Os > Ru Fe. 

Different from the ruthenium system previously discussed, [Ir(COD)Cl]2 reacted with the electron-rich olefin (217) to afford the homoleptic organoiridium tricycle complex (223) with an increase of the iridium oxidation state from (I) to (III) (equation 41). This spontaneous orthometallation process... 

Synthetic routes to homoleptic and heteroleptic tris(diimine)ruthenium(II) complexes incorporating bidentate imine ligands and used, particularly, as photosensitizers in transformations of solar energy to chemical or electric energy 04CCR(248)1329. 

Figure 7 Transient resonance Raman spectra of homoleptic and heteroleptic complexes of ruthenium(II) with bipyridine and bip5razine (adapted from ref. 9).

Another family of phosphane ligands that contain a phosphine unit and stericaUy shielded nitrogen lone pairs in the ligand periphery are the so-called AZARYPHOS (aza-aryl-phosphane, L) ligands. The incorporation of these ligands into homoleptic ruthenium complexes [RuCp(L)2(MeCN)][PF6], either preformed [86] or generated in situ [87], provides catalysts for the anti-Markovnikov hydration of terminal... 

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