Square planar ruthenium complex

A ruthenium complex, Ru(CO)2Cl2L, has been reported with ortfto-phenylenebis-(methylphenylarsine) (L) and there is a square-planar platinum complex (As—Pt 2.396 A) with the fully phenylated diarsine in which the metal atom also carries two p-(trifluoromethyl)phenyl groups . ... 

The reactivity of neutral square-planar d butatrienylidene complex 11 (Scheme 3.8) strongly deviates from that of cationic d ruthenium complexes. The deviation is readily understood when considering the orbital contributions of the metal and the carbon atoms of the chain to the LUMO. In d and d complexes the LUMO is predominantly localized at the metal, at Cl and C3. However, the relative contribution of the metal in d and d complexes is significantly different. In d complexes the metal contributes considerably less than Cl and C3, in d complexes its contribution is approximately equal to that of Cl and C3. 

R. Flugel, B. Windmuller, O. Gevert, and H. Werner, Synthesis, Molecular Structure and Reactions of Stable Square-Planar 16-Electron Ruthenium(O) Complexes trans-[RuC1(NO)(PR3)2], Chem. Ber. 129, 1007-1013 (1996). 

Cobalt(iii) diketonate complexes generate alkyl peroxo adducts that can oxidize alkenes to oxiranes <1999IC1603>. 0-Phenylenebis(oxamate)-Iigated square-planar cobalt(iii) complexes catalyze high-yield epoxida-tions of unfunctionalized tri- and disubstituted alkenes <1997TL2377>. Low yields are obtained with terminal alkenes. Terminal alkenes can be converted smoothly to aldehydes using an epoxidation-isomerization with ruthenium(ii) porphyrin catalysts <2004AGE4950>. 

Jitsukawa, K., Shiozaki, H., Masuda, H. Epoxidation activities of mononuclear ruthenium-oxo complexes with a square planar 6,6 -bis(benzoylamino)-2,2 -bipyridine and axial ligands. Tetrahedron Lett. 2002, 43,1491-1494. 

Ruthenium(II) phthalocyanine has been reported by Kreuger and Kenney 193). It is formed by the reaction of ruthenium trichloride and o-cyanobenzamide, and sublimes with difficulty. It is presumably square planar, although no magnetic data were recorded, and like ferrous phthalocyanine it forms adducts with aniline and o-toluidine containing six molecules of base. It is stable in concentrated sulfuric acid but is not oxidized in hydrochloric acid suspension. There is obviously much scope for further study, particularly with regard to higher oxidation state complexes. 

Almost 40 years ago, cisplatin, a square planar coordination compound of platinum(II), was found to be an effective antitumor agent. It forms complexes with some of the nitrogen bases of DNA, producing mutations during the replication of cancer cells. Second-generation square-planar platinum(II) complexes such as carboplatin and oxaliplatin that have less severe side effects are now available. Octahedral platinum(IV) complexes such as satraplatin as well as triplatin, a tri-nuclear platinum(II) complex, are in various stages of development. A new class of ruthenium(III) anticancer complexes hold promise of targeting additional cancer types with fewer side effects. 

Oxidative additions are particularly common for square-planar complexes the electronic configuration of the metal changes from rf to d. Oxidative eliminations are common for complexes, which give products. Oxidations of d centres to d are less common, though a recent example will be found in the section on ruthenium below. Indeed, for ruthenium, both d -> d, i.e. ruthenium(n) to ruthenium(iv), and J d i.e. ruthenium(o) to ruthenium(n), processes are possible. Again, for platinum, [Pg.350]

Non-metathetical reactions catalysed by ruthenium-carbene complexes are multifaceted and cover a broad range of transformations, thanks in part to the large number of oxidation states and coordination geometries available for the metal centre, in sharp contrast with other elements such as rhodium, palladium and platinum, which reluctantly form compounds with high oxidation states and have a strong preference for the square planar geometry. Several... 

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