Ruthenium ruthenocene

A significant step was made by neutron irradiation of ruthenocene. It was found that 20—25% of the ruthenium activity was recoverable as ruthenocene, and that also considerable rhodium activity was sublimed along with the ruthenocene. The rhodium was identified as being rhodium dicyclopentadienide, produced in high yield by the decay of ruthenocene. 

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%. 

A very interesting result on ruthenocene showed that when fission product ruthenium was projected into dimeric cyclopentadiene, the yield of ruthenocene was quite low, while when monomeric cyclopentadiene was used, the yield was close to 100%. This was interpreted as involving a thermal reaction between the ruthenium atom and a cyclopentadiene monomer molecule, likely the simple displacement of an acid hydrogen. 

The radiochemistry of ruthenocene has been studied by Baumgartner and Reichold (9) and by Harbottle and Zahn (29). It is found that neutron irradiation of crystalline RuCp2 yields about 10% of the radioactive ruthenium as RuCp2- More specifically, an isotopic difference in the radiochemical yield is found Ru, 9.6 0.1% Ru, 10.7 0.2% and Ru, 9.9 0.2% (29). In liquid solution the isotopic effect is much more pronounced, although the yields are lower. This was suggested by Harbottle as a general principle the greatest isotope effects are associated with the lowest yields. While this principle has not yet been substantiated, it seems reasonable since any thermal reactions which may increase the yields would not likely show any isotope effect. 

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. 

B. BIS(i/ -2,4-DIMETHYLPENTADIENYL)RUTHENIUM ( OPEN RUTHENOCENE ), RuCi/ -CsHsMCi) ... 

The yield reported here is based on the total amount of ruthenium (both Rum and Ru°) available for formation of ruthenocene. An additional quantity of ruthenocene may be obtained by extraction of the pyrophoric residue from the sublimation step with benzene in a Soxhlet extractor under a nitrogen atmosphere. The benzene solution is filtered through activated alumina, the solvent evaporated, and the residue sublimed. 

Ruthenocene has been prepared in 20% yields by reaction of cyclopentadienylmagnesium bromide with ruthenium(III) acetyl-acetonate.8 More recently,4 the compound has been made in 43-52% yield by treatment of sodium cyclopentadienide with ruthenium trichloride in tetrahydrofuran or 1,2-dimethoxyethane. 

The dicyclopentadienyl metal compounds undergo Friedel-Crafts alkylation and acylation, sulfonation, metalation, arylation, and formyla-tion in the case of ferrocene, dicyclopentadienyl ruthenium, and dicyclopentadienyl osmium, whereas the others are unstable to such reactions ( ). Competition experiments (128) gave the order of electrophilic reactivity as ferrocene > ruthenocene > osmocene and the reverse for nucleophilic substitution of the first two by n-butyl lithium. A similar rate sequence applies to the acid-catalysed cleavage of the cyclopentadienyl silicon bonds in trimethylsilylferrocene and related compounds (129), a process known to occur by electrophilic substitution for aryl-silicon bonds (130). 

Ruthenocene [bis-(cyclopentadienyl)ruthenium] [I287-I3-4] M 231.2, m 195.5 , 199-210 . Sublime in high vacuum at 120 . Yellow crystals which can be recrystallised from CCI4 as transparent plates. (7ACS74 6146 1952]. 

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. 

Open ruthenocenes have been obtained by reaction of hydrated ruthenium trichloride with methylated pentadienes in ethanol in the presence of zinc dust... 

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. 

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-... 

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