132373-99-0Relevant articles and documents
Organometallic clusters with face-capping arene ligands. 4. Tris(cyclopentadienylcobalt) clusters with μ3-alkenyl- and μ3-alkylbenzenes
Wadepohl, Hubert,Büchner, Klaus,Herrmann, Michael,Pritzkow, Hans
, p. 861 - 871 (2008/10/08)
The (CpCo)3(μ3-(1-alkenyl)benzene) clusters 5a,b and 6a,b are prepared from CpCo(C2H4)2 (3) and α-methylstyrene, β-methylstyrene, 1,1-diphenylethylene, and stilbene. From 3 and 4-methoxystilbene a mixture of the coordination isomers of (CpCo)3(μ3-4-methoxystilbene) (7a,b) is obtained. (CpCo)3(μ3-1,1-diphenylpropene) (10) is formed from 1,1-diphenylpropene and CpCo(C6Me6) (4). Styrene and 3 do not give a μ3-styrene cluster, but (CpCo)3(μ3-4-methylstyrene) (8) and (CpCo)3(μ3-4-methoxystyrene) (9) are isolated in good yield from the reaction of 3 and the corresponding substituted styrenes. Allylbenzene, 4-methoxy(allyl)benzene, and 4-phenyl-1-butene are catalytically rearranged by 3 or 4 to the (1-alkenyl)benzene derivatives. By reaction of the further ligands with 3 molar equiv of 3 the (CpCo)3(μ3-(1-alkenyl)arene) complexes 5b, 11, and 12 are formed. The X-ray crystal structures of 5b and 6a have been determined. Crystal data: 5b, monoclinic, P21, a = 8.725 (5) A?, b = 7.542 (5) A?, c = 15.151 (6) A?, β = 103.17 (4)°, Z = 2, R = 0.026, Rw = 0.027 (w = σ-2(F)) with 2893 reflections; 6a·0.5C7H8, triclinic, P1, a = 8.734 (4) A?, b = 11.470 (5) A?, c = 12.791 (6) A?, α = 85.37 (3)°, β = 83.81 (3)°, γ = 83.52 (3)°, Z = 2, R = 0.043, Rw = 0.038 (w = σ-2(F)) with 5795 reflections. The face-capping arene rings in both compounds are coplanar with the (CpCo)3 triangles and adopt a staggered orientation. Bond length alternation within the μ3-η2:η2:η 2-coordinated arene rings is only slight, with a mean difference of 0.03 A? between longer and shorter carbon-carbon bonds. In solution rotation of the arenes on top of the (CpCo)3 triangles takes place, which can be frozen out at low temperature. The chemical reactivity of the title compounds is low. The μ3-arene ligands cannot be displaced by other arenes or by two-electron donors. Bromination, hydrosilylation, and cyclopropanation of the exocyclic alkenyl group of 5b cannot be achieved. However, catalytic hydrogenation of 5b to give (CpCo)3(μ3-n-propylbenzene) (18) proceeds readily. The relationship of the μ3-arene clusters to the metal surface adsorption states of benzene is discussed.
