Ruthenium complexes ruthenocenes

This procedure was first used to prepare ruthenocene and other ruthenium complexes of cyclic olefin (136). The acyclic ruthenocenes are pale yellow, air-stable materials, soluble in organic solvents and readily sublimed. One representative compound of the lanthanides, NdPl 3 (137), and one of the actinides, UP1 3 (138), have also been described. 

This type of sandwich complex, first reported with iron as the central metal, has now become widespread with ruthenium as well. Early routes to ruthenium complexes were modeled on iron chemistry, and used the AICI3-catalyzed exchange of a cyclopentadienyl ligand for an arene in ruthenocene, or reaction of CpRu(CO)2Cl with AlCb/arene. These methods are less successful with ruthenium than with iron, however, owing to the greater stability of ruthenocene. A mixture of arene, pentamethylcyclopentadiene, and RuCls in the Zn reduction method gives good yields of the mixed-sandwich cations. A... 

Ruthenium complexes having cyclopentadienyl ligands have also been extensiveK investigated. Because ruthenocene is relatively unreactive, much attention has been focused on mononuclear ruthenium complexes with one cyclopentadienyl ligand or ruthenium dimers having cyclopentadienyl ligands. 

Some spectroscopic studies on metallocenes are as follows Gas phase syndiesis of unsymmetrically substituted ruthenocenes have been prqiared by gas phase electrocyclic reactions of pentadieny] ruthenium complexes. In the continuing soies of ptqiers on the Mdssbauer spectra of ferrocenes, azaferrocenes and phosphaferrocenes have been examined. H NMR studies have been carried out on the compounds of iod(4)iruthenoceniums(II,IV). A series of multinuclear NMR and X-ray single crystal diffraction shidies of metallocene containing cryptands has been carried out in addition to coordination studies of these species. ... 

Ruthenocene, and other ruthenium complexes were shown by Cluff et al, some of which were labelled with H, were adsorbed on silica surfaces by grinding the polycrystalline materials with silica. The progress was monitored by H, C, and solid-state NMR spectroscopy. The transition from the crystal lattice to the surface species that are highly mobile is proven by strongly reduced chemical shift anisotropies and diminished dipolar interactions. The MAS spectra of surface-adsorbed ferrocene-da prove that the motion of the metallocenes on the surfaces is fast and nearly isotropic, as in solution. ... 

The silanol complex 57 exhibits a Si H M agostic interaction characterized by a /(Si-H) of 41 Hz and a Si-H distance of 1.70(7) It would be incautious to interpret such a low value of the Si-H coupling in terms of a significant Si-H bond activation, because the Si-H bond forms rather acute angles with the Si-C and Si-Si bonds (about 82 and 101°, respectively) and thus must have a considerable p character on silicon, which should contribute to the decrease of /(Si-H). The silanol ligand is -coordinate to ruthenium and the Ru-Si bond of 2.441(3) A is not exceptional, but the Si(SiMe3)3 deviates from the silanol plane by 19.0°, probably as a result of the Si-H interaction. Deprotonation of 57 by strong bases affords a neutral ruthenocene-like product. 

Ruthenium reacts with cyclopentadiene in ether to form a sandwich complex, a yellow crystalline compound, bis(cyclopentadiene) ruthenium(0), also known as ruthenocene. 

Reasonably similar observations can be made for the complexes bis(2,3,4-trimethyl-pentadienyl)ruthenium and bis(2,4-dimethylpentadienyl)chromium, both of which contain metals larger than iron. Thus, in ruthenocene and chromocene the average M-C bond distances have been found to be 2.196(3) and 2.169(4) A, respectively, whereas for their open analogs, the distances are quite comparable, if not actually shorter, at 2.188(3) and 2.165(4) A, respectively. Thus it does seem that the Fe-C bond distances in Fe(2,4-... 

The common metathesis reactions for the preparation of metallocenes, treating a metal salt MX2 with NaCp, are hampered in the case of ruthenium by the lack of suitable Ru salts. (Rul2 is commercially available, but is still not commonly used in the synthesis of rathenocene.) Thus, ruthenocene has been obtained from Ru(acac)3 and NaCp in very low yield and later from RuCb and NaCp in 50-60% yield. It has now become apparent that alkene polymers, in particular [Ru(nbd)Cl2]x, but also [Ru(cod)Cl2]x and hydrazine derivatives (Section 3.1), can serve as Ru precursors. Equally successful in many cases is reductive complexation of cyclopentadiene in ethanol in the presence of Zn (Section 3.2), which furnishes the metallocene in about 80% yield. Decamethylruthenocene (82) was first obtained by the Zn reduction route in 20% yield, but can now be prepared conveniently from halide complexes [Cp RuCl2]2 or [Cp RuCl]4, a common method for the preparation of symmetrical and unsymmetrical sandwich compounds of ruthenium featuring one alkyl-substituted ligand. 

Ruthenium has played a central role in the development of 30 valence electron triple-decker cations of the iron group. These compounds were first prepared by Rybinskaya eto/., through reaction of a 12 valence electron [CpRu]+ fragment with a metallocene. The well-known photofragmentation of [CpFe(arene)]+ was used to generate [FeCp]+, which was then complexed to ruthenocene in situ. The stmcture of the triple-decker shows three exactly parallel rings, two of them (one outer and the inner) echpsed and... 

Aromatization of the ligand is a major driving force in the C-C bond-cleavage reaction. For example, sp C-sp C bond cleavage in (pentamethylcydohexadienyl)ruthe-nium is reported to give ruthenocene derivatives (Scheme 14.23) [54]. In this reaction, a Bronsted base is believed to promote demethylation from the exo face similar reactions are documented for cationic ruthenium(II) complexes [55-57]. 

Ruthenium, the homologue of iron in this group, was also shown to form complexes quite early. Ruthenocene, Ru( 5H5)2, is obtained by treatment of the acetylacetonate of tervalent ruthenium with five times the theoretical quantity of the Grignard reagent (206), or, better, by the action of cyclopentadienyl sodium on ruthenium trichloride in tetrahydrofuran (47). It forms pale yellow scales which sublime at 120° and melt at 200°. Its properties are closely similar to those of ferrocene it is soluble in organic solvents, and in the absence of air is not attacked by bases or by sulfuric or hydrochloric acid. Oxidation converts it into the pale yellow [Ru( 5H6)2] + ion. 

The d oxidative addition may seem unfamiliar because there are many more examples 47) of d d and d d processes. However, ruthenocene, which is sl (P ruthenium (II) complex with a delocalized electronic structure, undergoes two-electron oxidative addition by I2 and Br2 to give the Ru(IV) complexes Ru(cp)2r and Ru(cp)2Br (48). X-ray studies of Ru(cp)2r show that it is eflFectively a seven-co-ordinate complex (48). 

H NMR spectra (DMSO-dg) of the Ag" complexes of ruthenocenophanes (81) and (82) suggest no interaction between the ruthenium and the complexed silver ion. In this case, the methylene protons attached to sulfur atoms were shifted more than the protons of the ruthenocene nucleus. H NMR spectra of the mercury(II) complexes of (80)-(82) suggest that there is signihcant interaction between ruthenium and the mercury(II). The P protons of the Cp rings were shifted further downfield than the a protons, and the ethylene protons exhibited very little downfield shift <85BCJ3540>. 

IR spectral data of the mercury(II) and silver(I) complexes of ruthenocenophanes (80)-(82) have been used to help determine the extent of interaction between the ruthenium atom of the ruthenocene unit and the encapsulated metal ion. The Cp—Ru—Cp ring tilting band around 430 cm is very instructive in these studies <85BCJ3540). 

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