The Aromatization of C₅ Rings on a Heteronuclear Cluster

Abstract

The reaction of the heteronuclear cluster RuOs3(μ‐H)2(CO)13 with saturated and unsaturated C5 rings led to the aromatization of the rings to afford the clusters RuOs3(μ‐H)(CO)9(μ‐CO)2(η5‐C5R4R′). However, the reaction with cyclopentene gave the cluster RuOs3(μ‐H)3(CO)11(μ,η1:η2‐C5H7) via C–H activation of an sp2 carbon instead. Thermolysis of two of the products, RuOs3(μ‐H)(CO)9(μ‐CO)2(η5‐Cp′) and RuOs3(μ‐H)(CO)9(μ‐CO)2(η5‐C5H4SiMe3), led to their isomerization to butterfly clusters.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)

Reaction of the heteronuclear cluster RuOs3(μ-H)2(CO)13 with azulenes

“…The ruthenium atom capped by the five-membered ring occupies an equatorial position in the metal core. This is consistent with that observed for the closely related indene analogue Ru 2 Os 3 (m-H)(CO) 11 (m 3 ,h 5 :h 2 :h 2 -C 9 H 7 ) [24], and other trigonal bipyramidal pentanuclear ruthenium and osmium clusters containing cyclopentadienyl or arene ligands; without exception, the aromatic ligand always occupies an equatorial position on the pentanuclear metal framework. It has been suggested that having the M(h 5 -C 5 H 5 ) fragment in the equatorial position enhances distribution of electron density from the equatorial to the axial sites, thereby stabilizing the cluster [47].…”

“…Clusters 5a and 5b can be envisaged as having been formed by the addition of an 'Ru(h 5 -azulene)(CO) 2 ' fragment, from decomposition of the tetrahedral cluster RuOs 3 (m-H)(CO) 9 (m-CO) 2 (h 5 -azulene), to 1 followed by a cluster-to-ligand hydrogen atom migration and oxidative addition of the organic moiety. This pathway is similar to that proposed earlier for the cluster Ru 2 Os 3 (m-H) 2 (CO) 13 (m-CO)(m 3 ,h 5 :s 2 -C 5 H 3 C 3 H 7 ) [27]. Unfortunately, we have not been able to isolate either RuOs 3 (m-H)(CO) 9 (m-CO) 2 (h 5 -azulene) or an 'Ru(h 5 -azulene)(CO) 2 ' moiety.…”