Abstract
A study of the halogenation of [{Ru(π-C5H5)(CO)2}2] has revealed that while neutral [Ru(π-C5H5)(CO)2X](X = Cl, Br, or I) is formed in solvents such as dichloromethane and chloroform, salts of the cation [{Ru(π-C5H5)(CO)2}2X]+ separate from those reactions performed in benzene or toluene and in the presence of large counterions such as PF6 . It is shown that the cationic species [{Ru(π-C5H5)(CO)2}2X]+ is readily susceptible to attack by halides and pseudo-halides to yield products according to the scheme [{Ru(π-C5H5)(CO)2}2X]++ Y→[Ru(π-C5H5)(CO)2X]+[Ru(π-C5H5)(CO)2Y] The mechanism of formation of [Ru(π-C5H5)(CO)2X] from [{Ru(π-C5H5)(CO)2}2] is discussed in terms of this scheme. The cations [{Ru(π-C5H5)(CO)2}2X]+(X = Cl and Br) also react readily with the anion BPh4 . Fission of a boron–carbon bond in BPh4 and transfer of a phenyl group to a ruthenium atom is effected, to yield [Ru(π-C5H5)(CO)2Ph] and [Ru(π-C5H5)(CO)2X]. The cyanide and not a phenyl group is extracted from BPh3CN on reaction with [{Ru(π-C5H5)(CO)2}2X]+(X = Cl or Br) in acetone under reflux to give [Ru(π-C5H5)(CO)2CN] and [Ru(π-C5H5)(CO)2X]; the zwitterionic species [Ru+(π-C5H5)(CO)2NCB-Ph3] is shown to be an intermediate in the reaction.

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