Ruthenocene structure

The structure of ferrocene and an MO description of its bonding have already been given (p. 937). The rings are virtually eclipsed as they are in the analogous ruthenocene (light-yellow, mp 199°C) and osmocene (white, mp 229°C). 

Synthesis of ruthenocene from fission-product ruthenium isotopes was done by neutron irradiation ofU30g and FeCpj powder mixtures. It was shown that most of the ruthenocene found was actually produced by the decay of a precursor. Subsequent knowledge makes it apparent that the fission product recoils formed a rhodium dicyclopentadienide whose structure was preserved through the decay . The total yield of ruthenocene reached a value of 60% under some experimental conditions and was rarely less than 40%. 

It would also be interesting to check the ability of the ruthenocene acrylonitrile cation-radical to rotate around the ethylene bond Ruthenocenyl is weaker than ferrocenyl as a donor substituent (Laus et al. 2005). The particular property of rotating around the ethylenic bond in cation-radicals is a method of elucidating an electronic structure. 

While metallocenes are usually acetylated with acid halides, acid anhydrides, or carboxylic acids, a number of other acylating agents have been reported. The reaction of ferrocene with various isocyanates and aluminum chlorides leads to N-substituted ferrocenecarboxamides (IX) (89). Use of ruthenocene in place of ferrocene leads to analogous results (88). The preparation of V-phenyl-ferrocenecarboxamide from phenyl isocyanate in this manner has been used as a proof of structure for the product obtained from the Beckmann rearrangement of benzoylferrocene oxime (124). 

The traditional names ferrocene, manganocene, ruthenocene, nickelocene, etc. are given to the respective bis(ri5-cyclopentadienyl)metal complexes. Ocene names should not be coined for isoelectronic species such as chromocene for bis(ri6-benzene)chromium, for structurally analogous... 

Ferrocene is only one of a large number of compounds of transition metals with the cyclopentadienyl anion. Other metals that form sandwich-type structures similar to ferrocene include nickel, titanium, cobalt, ruthenium, zirconium, and osmium. The stability of metallocenes varies greatly with the metal and its oxidation state ferrocene, ruthenocene, and osmocene are particularly stable because in each the metal achieves the electronic configuration of an inert gas. Almost the ultimate in resistance to oxidative attack is reached in (C5H5)2Co , cobalticinium ion, which can be recovered from boiling aqua regia (a mixture of concentrated nitric and hydrochloric acids named for its ability to dissolve platinum and gold). In cobalticinium ion, the metal has the 18 outer-shell electrons characteristic of krypton. 

The reaction of 1,3-diboroles 4, LiMe and [ (C5Me5)RuCl 4] leads to the violet, highly air-sensitive Ru sandwich complexes 1810. The compounds 17 and 18 are derived from ferrocene and ruthenocene by formal replacement of two CH groups for B-R units. Therefore the complexes should have only 16 valence electrons (VE). However, the electronic structure of the iron compound 17, studied by EH-MO theory, exhibits a unique bonding The electron density of two B-C c orbitals participates in the bonding by... 

Ruthenocene, Ru(Cp)2 [2,67,68. The analysis of the emission spectrum of this molecule provides another example of the determination of multiple distortions by using time-dependent theory. The spectrum is more complicated than that of the previous example because it contains two well separated origins and the distortions are much bigger. This example shows the effects of large distortions on the shape of the emission spectrum as discussed in Section III.E.l. It also provides an example of the effect of many modes which have significant displacements on the vibronic structure of the emission spectrum (Section III.E.3). The relationship between the distortions and the molecular orbitals involved in the one-electron transition is discussed. 

The appearance of nontotally symmetric modes in the emission spectrum has important ramifications to the structure of the excited state. Because they do appear, the point group of the excited state of ruthenocene is lower than Djh. The point group in the excited state must be one in which these vibrational modes are totally symmetric. The point group which satisfies this condition is C,. In this symmetry, the 445 cm ring-metal stretch and one component of the ring tilt mode are totally symmetric. The involvement of... 

A striking feature in the vibronic structure of the low temperature emission spectrum of ruthenocene is a repetitive pattern of clusters of bands. The pattern consists of the main peak and three side-peaks which are separated from the main peak by about 47 cm , 65 cm , and 112 cm . The first two side peaks are often not well resolved. The separation between the bands within a cluster is less than the energy of any normal mode. A possible explanation for the side-peaks could be phonon wings on the main 333 cm progression. However, the spectra obtained from organic glasses contain the same repetitive pattern. Thus the structure must arise from molecular normal modes and not from crystal lattice modes. 

Although the previously observed phosphorescence of ferrocene now appears to have been artlfactual, a fairly strong luminescence has been observed from the analogous ruthenium(II) compound (53,210). The emission spectrum of ruthenocene, measured at low temperatures either from the pure solid or from glassy media, appears as a rather broad but highly structured band centered around a maximum at about 17 kK. The lifetime of the emission from the solid is strongly temperature dependent. 

Ferrocene is reduced to [FeCp2] in dme. The process is chemically reversible at -45°C, but large CV peak separations may imply structural distortion in the anion (539). By contrast to ruthenocene, [Ru(fj-C5Me5)2] gives a stable monocation (540) (Section X,E). 

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