Activation of triruthenium carbonyl complexes by incorporation of hemilabile ancillary ligands containing alkoxo, amido, or thiolato groups. Generation of a reactive alkenyl complex

Article abstract of DOI:10.1021/om00039a046

The alkoxo, amido, or thiolato groups derived respectively from 2-hydroxypyridine, 2-anilinopyridine, or 2-mercaptopyridine are incorporated into Ru₃(CO)₁₂ to give several activated anionic and neutral complexes. The anions [Ru₃(μ-η²-X(C₅H₄N))(CO) ₁₀]^- (1a,c) and [Ru₃(μ₃-η²-X(C₅H ₄N))(CO)₉]^- (2a,b): a, X = N(C₆H₅); b, X = S; c, X = O) are obtained (i) in 80-90% yield by treatment of Ru₃(CO)₁₂ with K[X(C₅H₄N)] followed by metathesis with (PPN)Cl (PPN = (C₆H₅)₃PNP(C₆H₆) ₃⁺) or (ii) by reaction of HX(C₅H₄N) with PPN[Ru₃(μ-H)(CO)₁₁] (refluxing THF, 2 h, 60% yield). The amido derivatives 1a-3a are also available via method iii, involving direct reaction of 2-anilinopyridine with Ru₃(CO)₁₂ (refluxing benzene, 2 h) to give Ru₃(μ-H)(μ₃-η²-N(C₆H ₅)(C₅H₄N))(CO)₉ (3a) (yield 85%). The latter is subsequently deprotonated by PPNBH₄ to give 2a (yield 90%). The sulfido derivative Ru₃(μ-H)(μ₃-η²-S(C₅H ₄N))(CO)₉ (3b) is obtained in 80-90% yield by protonation of the potassium salt of 2b. The X-ray structures of the PPN salts of 1c and 2a are reported. Crystallographic data for PPN·1c: triclinic P1 (No. 2), a = 13.209 (1) A?, b = 18.149 (2) A?, c = 11.217 (2) A?, α = 102.37 (1)°, β = 96.52 (1)°, γ = 107.40 (1)°, V = 2461 A?³, Z = 2; μ(Mo Kα) = 10.15 cm^-1; R = 0.042, R_w = 0.043 for 7330 observations and 382 variables. Crystallographic data for PPN·2a: triclinic P1 (No. 2), a = 15.933 (2) A?, b = 17.163 (2) A?, c = 10.384 (2) A?, α = 102.69 (1)°, β = 91.06 (1)°, γ = 107.55 (1)°, V = 2630 A?³, Z = 2; μ(Mo Kα) = 8.64 cm^-1; R = 0.042, R_w = 0.042 for 5665 observations and 364 variables. On the basis of these structures, it is suggested that the variable hapticity of group X (terminal position in 1 and bridging position in 2) plays a lightly stabilizing role for coordination sites. The hydrido complexes Ru₃(μ-H)(μ₃-η²-X(C₅H ₄N))(CO)₉ (3a,b) react cleanly with alkynes (40-50°C, 30-45 min) to give selectively the corresponding alkenyl complexes Ru₃(μ₃(η²-X-(C₅H ₄N))(μ-(C₆H₅)CCH(C₆H ₅))(CO)₈ (4a, 90-95% yield; 4b, 70-80% yield) via cis insertion into the metal-hydride bond. The X-ray structure of 4a has been determined. Crystallographic data for 4a (crystallizing with 1 mol of CH₂Cl₂ per unit cell): triclinic P1 (No. 2), a = 10.424 (1) A?, b = 18.795 (2) A?, c = 8.964 (1) A?, α = 93.97 (1)°, β = 105.09 (1)°, γ = 78.51 (1)°, V = 1661 (5) A?³, Z = 2; μ(Mo Kα) = 13.76 cm^-1; R = 0.023, R_W = 0.025 for 5502 reflections and 436 variables. The cluster consists of a trinuclear ruthenium unit supported by a face-bridging phenylpyridylamido group. The bridging alkenyl group is coordinated at equatorial sites and spans a metal-metal edge adjacent to that supported by the bridging amido group. There is a bridging carbonyl spanning the same edge as the amido group. The features which may account for the high reactivity of this complex are discussed.