Facile Changes in Bonding Modes of Azulene in Di- and Triruthenium Clusters upon Interaction with CO

Abstract

Carbonylation of the known cluster [Ru 3 (CO) 6 (μ-CO)(μ 3 -η 5:η 3:η 3 −C 10 H 8 )] ( 1 ) gives the metastable trinuclear derivative [Ru 3 (CO) 8 (μ 3 -η 5:η 2:η 1 -C 10 H 8 )] ( 2 ). On further carbonylation of 1 the stable product [Ru 2 (CO) 5 (μ 2 -η 5:η 3 -C 10 H 8 )] ( 3 ) is obtained. X-ray diffraction studies and full spectroscopic assignment of 3 show that the azulene ligand is bonded through a π-Cp to one metal and via a π-allyl moiety to the other. Compound 3 reacts reversibly with CO to yield [Ru 2 (CO) 6 (μ 2 -η 5:η 1 -C 10 H 8 )] ( 4 ), which maintains the π-Cp bond while the heptadienyl ring contributes to the bonding only through one σ-C−Ru interaction.