The indenyl complex [RuCl(η 5 -C 9 H 7 )(PPh 3 ) 2 ] (1) reacts with monodentate (L: PMePh 2 , PMe 2 Ph, PMe 3 ) or bidentate [L-L: Ph 2 PCH 2 PPh 2 (dppm), Ph 2 P(CH 2 ) 2 PPh 2 (dppe)] phosphines to give monosubstituted [RuCl(η 5 -C 9 H 7 )(PPh 3 )(L)], bisubstituted [RuCl(η 5 -C 9 H 7 )(L) 2 ], or chelated complexes [RuCl(η 5 -C 9 H 7 )(L-L)] in toluene or tetrahydrofuran. The corresponding cyclopentadienyl complex [RuCl(η 5 -C 5 H 5 )(PPh 3 ) 2 ] (2) reacts similarly, at higher temperatures or longer reaction times. In refluxing toluene, PMe 3 and dppm give ionic products [Ru(η 5 -C 9 H 7 )(L) 3 ]Cl. The kinetics of PPh 3 substitution by PMePh 2 and PMe 2 Ph in tetrahydrofuran yield first-order rate constants that are independent of the concentration or the nature of phosphine. Rate decrease in the presence of added PPh 3 or saturation behavior at high [PPh 3 ] indicates that the reaction proceeds by a dissociative mechanism, in which extrusion of PPh 3 is rate determining. Kinetics for the reaction with PMePh 2 in the temperature range 12-40 °C for the indenyl and 20-50 °C for the cyclopentadienyl complex give the following activation parameters: ∆H q) 26 ( 1 kcal mol -1 and ∆S q ) 11 ( 2 cal mol -1 K -1 for 1 and ∆H q) 29 ( 1 kcal mol -1 and ∆S q ) 17 ( 2 cal mol -1 K -1 for 2. Complex 1 is 1 order of magnitude more reactive than 2, indicating more efficient stabilization of 16-electron intermediates RuCl(η 5 -ligand)(PPh 3 ) by the indenyl group. Cyclic voltammetry measurements for [RuCl(η 5 -ligand)(L) 2 ] in dichloromethane indicate that indenyl or pentamethylcyclopentadienyl complexes are oxidized at lower potentials than cyclopentadienyl complexes. Kinetics and electrochemistry suggest that indenyl is electron donating toward the metal fragment, with respect to cyclopentadienyl.

The indenyl complexes [RuX(η 5 -C 9 H 7 )(dppm)] (dppm ) bis(diphenylphosphino)methane, X ) H, D) react with phenylacetylene to give the products of syn addition [Ru{(E)-CHdCXPh}(η 5 -C 9 H 7 )(dppm)] in toluene, in the temperature range 40-80 °C. The indenyl complexes [RuH(η 5 -C 9 H 7 )LL′] (L ) L′ ) PMe 2 Ph; L ) PPh 3 , L′ ) PMe 2 Ph; L ) PPh 3 , L′ ) PMe 3 ; LL′ ) dppe) and [RuH(η 5 -Me 3 C 9 H 4 )(CO)(PPh 3 )] and the cyclopentadienyl complex [RuH(η 5 -C 5 H 5 )(dppm)] do not react with PhCtCH, even under more forcing conditions. The complexes [RuH(η 5 -C 9 H 7 )LL′] (LL′ ) dppe; LL′ ) dppm; L ) L′ ) PMe 2 Ph; L ) PPh 3 , L′ ) PMe 3 ; L ) PPh 3 , L′ ) PMe 2 Ph) and the indenyl-substituted complexes [RuH(η 5 -Me 3 C 9 H 4 )(CO)(PR 3 )] (PR 3 ) PPh 3 , P i Pr 3 ) react with dimethyl acetylenedicarboxylate to give the alkenyl derivatives [Ru{(E)-C(CO 2 Me)dCH(CO 2 Me)}(η 5 -C 9 H 7 )LL′] and [Ru{(E)-C(CO 2 -Me)dCH(CO 2 Me)}(η 5 -Me 3 C 9 H 4 )(CO)(PR 3 )], respectively, in diethyl ether under reflux. The reaction of [RuH(η 5 -C 9 H 7 )LL′] with methyl propiolate yields the R-metalated alkenyl complexes [Ru{C(CO 2 Me)dCH 2 }(η 5 -C 9 H 7 )LL′] (LL′ ) dppe, dppm; L ) L′ ) PMe 2 Ph; L ) PPh 3 , L′ ) PMe 3 ) in refluxing diethyl ether. A kinetic study has been carried out for the reaction of the complexes [RuX(η 5 -C 9 H 7 )(dppm)] with phenylacetylene in toluene, by 1 H and 31 P{ 1 H} NMR spectroscopy. The reactions are first order with respect to the ruthenium complex and to the alkyne. The hydride and the deuteride complexes react at the same rate; intermediates are not detectable neither by kinetic studies nor by spectroscopy. The activation parameters, from rate measurements in the range 40-60 °C, are as follows: ∆H q ) 17 ( 2 kcal mol -1 , ∆S q ) -21 ( 4 cal mol -1 K -1 . An associative mechanism is proposed for the reaction, which involves the formation of an intermediate from the ruthenium complex and the alkyne under rate-determining steady-state conditions, followed by fast hydride migration and product formation. Due to the lack of reactivity of the analogous cyclopentadienyl complex [RuH(η 5 -C 5 H 5 )(dppm)], the reaction represents a case of indenyl effect. On the other hand, the indenyl and the cyclopentadienyl complexes react at comparable rates with the activated alkyne methyl propiolate.