Pentamethylcyclopentadienyl ruthenium dichloride is an organoruthenium chemistry with the formula [(C<sub>5</sub>(CH<sub>3</sub>)<sub>5</sub>)RuCl<sub>2</sub>]<sub>2</sub>, commonly abbreviated [Cp*RuCl<sub>2</sub>]<sub>2</sub>. This brown paramagnetic solid is a reagent in organometallic chemistry. It is an unusual example of a compound that exists as isomers that differ in the intermetallic separation, a difference that is manifested in a number of physical properties.
The compound has C<sub>2h</sub> symmetry, with each metal atom having pseudo-octahedral geometry. In the crystal structure, two isomers are observed in the unit cell, one with a 2.93 àrutheniumâÂÂruthenium bond and the other with a long internuclear distance of 3.75 à. The former isomer is diamagnetic, and the latter is magnetic.
It is prepared by the reaction of hydrated ruthenium trichloride with pentamethylcyclopentadiene.
The reaction is accompanied by formation of decamethylruthenocene.
Pentamethylcyclopentadienyl ruthenium dichloride can reduced to the diamagnetic tetramer of Ru(II):
Methoxide also can be used to produce a related diruthenium(II) derivative, which is also diamagnetic:
Treating the tetramer with 1,5-cyclooctadiene in etheral solvent gives the mononuclear complex chloro(1,5-cyclooctadiene)(pentamethylcyclopentadienyl)ruthenium(II).
Compounds like Cp*RuCl(1,5-cyclooctadiene), the tetramer [Cp*RuCl]<sub>4</sub>, and related diamagnetic Cp*Ru(III) complexes have been investigated as hydrogenation catalysts.