135585-06-7Relevant academic research and scientific papers
(η6-Naphthalene)(η 4-1,5-cyclooctadiene)ruthenium(0): Efficient synthesis, chemistry, and catalytic properties
Bennett, Martin A.,Neumann, Horst,Thomas, Marian,Wang, Xian-Qi,Pertici, Paolo,Salvadori, Piero,Vitulli, Giovanni
, p. 3237 - 3245 (2008/10/08)
The ruthenium(0) complex (η4-1,5-cyclooctadiene)(η 6-naphthalene)ruthenium(0), Ru(η6-C10H8)(η4-C 8H12) (2), is conveniently synthesized in 55-64% yield on a gram scale by treatment of Ru(acac)2(η4-C8H12) (acac = acetylacetonate) with sodium naphthalide. A preliminary 1H NMR study of the rate of replacement of naphthalene by arenes in the presence of acetonitrile at room temperature has been made. The reaction is first order in 2 and approximately first order in acetonitrile up to [CH3CN]/[2] ca. 3, but a higher order for the latter cannot be excluded. Benzene, toluene, and xylene (8 mol per mol of 2) in THF-d8 replace naphthalene at almost the same rate, but the reaction is slower when there are more than two methyl groups in the entering arene, the order being p-xylene > 1,2,4-trimethylbenzene > 1,2,3,4-tetramethylbenzene ? mesitylene. The results are consistent with the initial formation of labile intermediate η4- or η2-naphthalene complexes that are stabilized by acetonitrile, e.g., Ru(η4-C10H8)(η4-C 8H12)(NCMe). Solutions of 2 in acetonitrile lose naphthalene to form a dinuclear μ-naphthalene complex Ru2(η4-C8H12) 2(μ-C10H8) (5). The new η6-arene complexes Ru(η6-arene)(η4-C8H12) (arene = C6H6CN (4), 1,2,4-C6H3Me3 (6), 1,2,3,4-C6H2Me4 (7), C6H6CH=CH2 (9), 1-Me-4-CH2=CMeC6H4 (10), (E)-C6H5CH=CHC6H5 (11), (C6H5)3As (14), and (2-MeC6H4)3P (15) have been obtained from 2, and the new ruthenium(II) complexes [RuCl2(η6-arene)]2 (12) and Ru(O2CMe)2(η6-arene) (13) (arene = 1-Me-4-CH2=CMeC6H4) have been prepared from 10. Protonation of 2 with HPF6 gives the hydridoruthenium(II) complex [RuH(η6-C10H8)(η4-C 8H12)]PF6 (16), from which naphthalene is readily displaced by p-xylene or mesitylene to give [RuH(η6-arene)(η4-C8H 12)]PF6. In the presence of acetonitrile and hydrogen (1-20 atm), 2 catalyzes the hydrogenation of olefins. It is much more active than Ru(η6-arene)(η4-C8H12) (arene = C6H6, 1-Me-4-Me2CHC6H4) under the same conditions, probably as a consequence of the ease of η6 → η4 conversion for naphthalene.
