Insertion Reactions of Alkynes into the Ru−H Bond of Indenylruthenium(II) Hydride Complexes. Mechanism of the Reaction of Phenylacetylene with [RuH(η⁵-C₉H₇)(dppm)] (dppm = Bis(diphenylphosphino)methane)

Abstract

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.

Regioselective Synthesis of Indenylruthenium(II) Vinylalkylidene Complexes via Proton Additions to Vinylalkenyl Derivatives

“…All the alkenyl complexes are isolated as orange solids and have been characterized by elemental analysis (see Experimental Section) and NMR ( 31 P{ 1 H}, 1 H, 13 C{ 1 H}) spectroscopy. The spectra exhibit resonances of the indenyl and dppm ligands in accordance with the proposed structures (see Tables and and Experimental Section). 31 P{ 1 H} NMR spectra (Table ) show a single signal ( 1a , b and 2a − c , δ 22.26−22.44; 3a , δ 23.11 ppm), indicating the chemical equivalence of both phosphorus atoms.…”

(Alkenylalkylidene)(indenyl)ruthenium(II) Complexes: Synthesis by Protonation of Alkenyl Derivatives

“…The 13 C{ 1 H} and 1 H NMR spectra show the expected resonances of the alkenyl groups which can be compared with those of the analogous (alkenyl)(dppm)ruthenium(II) complexes. [17] In particular, some resonances of the 1 H NMR spectra show coupling constants arising from a cis (geminal) arrangement for complex 4 (the relatively small J H,H ϭ 2.3 Hz of the nonequivalent vinylic protons indicates α-metalation) and an (E) configuration for complex 5 (the large proton coupling constant J H,H ϭ 15.9 Hz indicates the mutually trans arrangement). In order to confirm the stereochemistry of complex 3, an X-ray crystal structure determination has been carried out.…”

Reactivity of Hydride Half‐Sandwich Ruthenium(II) Complexes Bearing the Scorpionate Ligands Hydridotris(pyrazol‐1‐yl)borate and Tris(pyrazol‐1‐yl)methanesulfonate

“…The differences in the reactivity of the hydride complexes 2 and 3 are probably due to the steric hindrance of the PPh 3 ligands, as shown for the complexes [RuH(η 5 ‐C 9 H 7 )(PPh 3 )(PMe 2 Ph)] . Thus, the steric influence of the ancillary phosphane ligands is important, and the smaller cone angle of the pta (114°) compared with the PPh 3 (145°) ligand favours the insertion reactions of non‐activated alkynes.…”