110661-40-0Relevant academic research and scientific papers
Chemical transformations on phosphido-bridged clusters. Reactions of the μ3-η3-allenyl complex Ru3(CO)8{μ3-η3-CH 2CC(i-Pr)}(μ-PPh2). Reversible CO addition, adduct formation with P(OMe)3, hydrogenation, and alkyne insertion
Nucciarone, Donato,Taylor, Nicholas J.,Carty, Arthur J.
, p. 127 - 137 (2008/10/08)
Reactions of the allenyl cluster Ru3(CO)8{μ3-η3-CH 2CC(i-Pr)}(μ-PPh2) (1) with carbon monoxide, trimsthyl phosphite, dihydrogen, and alkynes are described. Addition of CO to 1 affords the 50-electron open cluster Ru3(CO)9{μ3-η3-CH 2CC(i-Pr)}(μ-PPh2) (3) via cleavage of the Ru-Ru bond bridged by the phosphido group. Labeling experiments (13CO) indicate regiospecific incorporation of the nucleophile trans to one arm of the phosphido bridge. Trimethyl phosphite reacts similarly giving an open 50-electron cluster 4. Complex 1 activates molecular hydrogen at room temperature and 1 atm leading to conversion of the allenyl group to a μ3-∥-acetylene hydride (μ-H)Ru3(CO)8{μ3-η 2-CH3C≡C(i-Pr)}(μ-PPh2) (5). Crystals of 5 from n-hexane are monoclinic, space group P21/c, with a = 14.582 (2) A?, b = 11.404 (3) A?, c = 18.496 (3) A?, β = 111.71 (1)°, V = 2857.6 (9) A?3, and Z = 4. The structure was solved by heavy-atom methods and refined to R and Rw values of 0.030 and 0.034, respectively, using 4170 observed reflections. The molecule consists of an asymmetric triangle of ruthenium atoms with a hydrido bridge across the Ru(1)-Ru(3) edge, a μ-PPh2 group bridging the Ru(1)-Ru(2) vector, and a multisite bound isopropylmethylacetylene ligand on the top face of the cluster. The conversion of 1 to 5 represents a useful synthetic route to unsymmetrical trinuclear acetylene clusters. In solution 5 exists as interconverting isomers. The reaction of 1 with alkynes results in coupling of the allenyl group and the acetylene to give the clusters Ru3(CO)7{μ3-η5-CH 2CC(i-Pr)C(R)C(R′)}(μ-PPh2) (R = R′ = Ph, 6; R = CH3, R′ = i-Pr, 7; R = i-Pr, R′ = CH3, 8; R = R′ = H, 9) which contain a wrap-around five-carbon hydrocarbon chain. Single-crystal X-ray analyses of 6 (crystal data: a = 12.130 (2) A°, b = 16.424 (2) A?, c = 18.766 (3). A?, β = 101.52 (1)°, V = 366.3 (8) A?3, Z = 4; R = 0.33, Rw = 0.038 on 6363 observed reflections) and 8 (crystal data: a = 9.690 (1) A?, b = 31.287 (5) A?, c = 10.908 (2) A?, β = 106.40 (1)°, V = 3172 (1) A?3; Z = 4; R = 0.027; Rw, = 0.032 on 4407 observed reflections) have revealed that while the hydrocarbyl-Ru3 frameworks are remarkably similar, the phosphido group is axial to the Ru3 triangle in 6 and equatorial in 8. The variable-temperature NMR spectra of 7-9 are explicable in terms of a hidden partner exchange process involving axial-equatorial phosphido bridge isomerism.
