Fluxional Behavior of a Perpendicularly Coordinated μ₃-Alkyne Ligand on a Triruthenium Cluster. Synthesis and Structure of a μ₃-η²:η²(⊥)-Cycloalkyne Complex

Abstract

Treatment of the triruthenium pentahydrido complex {Cp*Ru(μ-H)}3(μ3-H)2 (1; Cp* = η5-C 5Me5) with cycloalkene resulted in exclusive formation of the μ3-cycloalkyne complex {Cp*Ru(μ-H)}3(μ3-η2:η2(⊥)-C n H2 n - 4) (2a; n = 5, 2b; n = 6) as a result of vinylic C−H bond cleavage. VT NMR studies revealed fluxional behavior of the perpendicularly coordinated cycloalkyne ligand. Reaction of 2b with carbon monoxide afforded the 48-electron complex (Cp*Ru)3(μ-CO)(μ3-CO)(μ-H)(μ3-η2(∥)-C6H8) (3b) with a parallel-coordinated alkyne ligand.

Synthesis, structure, and property of a triruthenium cluster having a μ-alkyl ligand: Transformation of a μ3(⊥)-alkyne ligand into a μ-alkyl ligand via a μ3-vinylidene complex

“…At 23°C, the time-averaged spectrum showing two sharp Cp * signals with the intensity ratio of 2:1 was obtained. Although the motion was not completely frozen even at À90°C, free energy of activation, DG à , at the coalescence temperature (6); Ru(1)-C(1), 2.124(4); Ru(1)-C(7), 2.065(4); Ru(1)-C(8), 1.998(4); Ru(2)-C(7), 2.066(3); Ru(2)-C(8), 2.030(4); Ru(2)-C(9), 1.965(4); Ru(3)-C(1), 2.387(4); Ru(3)-C(7), 2.176(4); Ru(3)-C(9), 2088(4); Ru(3)-H(1), 1.89(6); C(1)-C(2), 1.542 (5); C(1)-H(1), 1.00 (6); C(1)-H(2), 1.12 (5); C(2)-C(3), 1.547 (5); C(7)-O(1), 1.208(4); C(8)-O(2), 1.182(5); C(9)-O(3), 1.184(4); Ru(1)-Ru(2)-Ru (3), 59.629 (15); (2), 59.742 (12); Ru(2)-Ru(1)-Ru (3), 60.629 (14); Ru(1)-C(1)-C(2), 118.9(2).…”

“…As mentioned in our previous communication, reaction of the (^)-cyclohexyne complex, {Cp * Ru(l-H)} 3 (l 3 -g 2 :g 2 (^)-cyclo-C 6 H 8 ) (3) with CO resulted in the formation of a (//)-cyclohexyne complex, (Cp * Ru) 3 (l 3 -g 2 -cyclo-C 6 H 8 )(l-H)(l-CO)(l 3 -CO) (4), with elimination of dihydrogen [14].…”

“…Complex 1c-in possesses a butyl group at the inner acetylenic carbon atom, and 1c-out lies in the opposite situation. These two isomers were rapidly converted between each other by way of switchback motion of the alkyne moiety at room temperature [14]. Gentle heating of 1c afforded a mixture of 1c and l 3 -hexenylidene complex, {Cp * Ru(l-H)} 3 (l 3 -g 2 -C@C n BuH) (5c).…”

“…(12); Ru(1)-C(1), 1.997 (6); Ru(1)-C(2), 2.033 (6); Ru(1)-C(4), 2.018 (7); Ru(2)-C(1), 2.013 (6); Ru(2)-C(2), 2.049 (6); Ru (2) (2), 59.96 (2); Ru(2)-Ru(1)-Ru (3), 59.91 (3). (2), 2.7095 (6); Ru(2)-Ru (3), 2.7464(6); Ru (1) (14); Ru(2)-Ru(1)-Ru (3), 60.921 (14).…”

The Ditertiary‐Phosphane‐Bridged Heteronuclear Cluster RuOs3(μ‐H)2(CO)9(μ‐CO)2(μ‐dppm): Synthesis and Reactivity with Alkynes

“…[17] More recently, a reversed scheme termed switchback motion has been suggested to explain the fluxional behavior of the triruthenium cluster [{Cp*Ru(µ-H)} 3 (µ 3 ,η 2 :η 2 -C 5 H 6 )]. [18] We have monitored the isomerization of 3c to 4c by 1 H NMR spectroscopy and found that it is a very slow process at ambient temperature. After five months at ambient temperature, the mixture was heated in refluxing hexane for 4 h in order to obtain the equilibrium concentrations.…”