The reaction of cyclopentadiene with dodecacarbonyltriruthenium: the isolation and crystal structure of tetracarbonylbis[dicarbonyl(η-cyclopentadienyl)ruthenio]ruthenium, [{Ru(η-C5H5)(CO)2}2Ru(CO)4]

Abstract

The new title compound (1) has been isolated, in addition to the normal product [{Ru(η-C₅H₅)(CO)₂}₂](2) from the reaction of cyclopentadiene and [Ru₃(CO)₁₂] in refluxing heptane. Its formation, which may represent an early stage of the reaction of the diene with the triruthenium cluster, is enhanced by short reaction times and by a low relative concentration of cyclopentadiene. Crystals of (1) are monoclinic, space group P2₁/c, with Z= 2 in a unit cell of dimensions a= 6.819(3), b= 11.757(3), c= 13.085(5)Å, and β= 110.84(2)°. The molecules are therefore centrosymmetric. The structure has been determined by heavy-atom methods from diffractometer data and refined to R 0.027 for 1 563 independent reflections. The three ruthenium atoms form a linear array [Ru–Ru 2.889(1)Å] with the cyclopentadienyl rings in a mutually trans relationship on the terminal metal atoms. The central metal atom has four equatorial carbonyl groups, while the terminal metal atoms each carry two carbonyl groups which are eclipsed relative to those on the central atom. The metal–carbonyl distances on the central atom are significantly longer than those on the terminal atoms.