TY - JOUR
T1 - Synthesis of and stereospecific hydride migration in cationic (tricyclic arene)(cyclooctadiene)ruthenium(II) complexes
AU - Hirano, Masafumi
AU - Shibasaki, Takao
AU - Komiya, Sanshiro
AU - Bennett, Martin A.
PY - 2002/12/23
Y1 - 2002/12/23
N2 - The (tricyclic arene)ruthenium(0) complex [Ru(η4-1,5-COD)(η6-phenanthrene)] (4) (COD = cyclooctadiene) is prepared by reduction of [Ru(acac)2(η4-1,5-COD)] (3) (acac = acetylacetonato) with sodium phenanthrene in 15% yield. Similar treatment of 3 with sodium anthracene gives a mixture of [Ru(η4-1,5-COD)(η6-anthracene)] (6) and [Ru(η4-1,5-COD)(η6-9,10-dihydroanthracene)] (7) in 3:1 molar ratio, from which only 7 can be isolated in a pure state. Protonation of 4 by HPF6 yields the cationic hydridoruthenium(II) complex [RuH(η4-1,5-COD)(η6-phenanthrene)]PF6, [5]PF6, in 53% yield, whereas similar protonation of 7 gives an equilibrium mixture of a hydrido diene complex [RuH(η4-1,5-COD)(η6-9,10-dihydroanthracene)]PF 6, [8]PF6, and an agostic cyclooctenyl complex [Ru(η1,η3-C8H13)(η6 -9,10-dihydroanthracene)]PF6, [9]PF6, in 4:1 molar ratio at 295 K in CD2Cl2, in which the endomethylene protons of the COD ligand and the agostic hydride in [9]PF6 exchange rapidly on the NMR time scale, even at 193 K. Thermodynamic parameters for the equilibrium between [8]PF6 and [9]PF6 in acetone-d6 have been derived from variable-temperature NMR experiments; ΔH° = -12 ± 1 kJ mol-1, ΔG° = 1 ± 2 kJ mol-1, and ΔS° = -44 ± 4 J K-1 mol-1. The large negative entropy is consistent with the agostic formulation. As expected, the η3-cyclooctenyl complex can be trapped as [Ru(1-3-η3-C8H13)(η6-9,10-di hydroanthracene)-(CO)]PF6, [10]PF6, in 80% yield on exposure of the equilibrium mixture of [8]PF6 and [9]PF6 to an atmosphere of CO. Addition of D2O to the equilibrium mixture leads to selective facile deuteration of the hydride and endo-methylene protons of the 1,5-COD and cyclooctenyl ligands. Such endo-selective H/D exchange reaction is also observed for [5]PF6.
AB - The (tricyclic arene)ruthenium(0) complex [Ru(η4-1,5-COD)(η6-phenanthrene)] (4) (COD = cyclooctadiene) is prepared by reduction of [Ru(acac)2(η4-1,5-COD)] (3) (acac = acetylacetonato) with sodium phenanthrene in 15% yield. Similar treatment of 3 with sodium anthracene gives a mixture of [Ru(η4-1,5-COD)(η6-anthracene)] (6) and [Ru(η4-1,5-COD)(η6-9,10-dihydroanthracene)] (7) in 3:1 molar ratio, from which only 7 can be isolated in a pure state. Protonation of 4 by HPF6 yields the cationic hydridoruthenium(II) complex [RuH(η4-1,5-COD)(η6-phenanthrene)]PF6, [5]PF6, in 53% yield, whereas similar protonation of 7 gives an equilibrium mixture of a hydrido diene complex [RuH(η4-1,5-COD)(η6-9,10-dihydroanthracene)]PF 6, [8]PF6, and an agostic cyclooctenyl complex [Ru(η1,η3-C8H13)(η6 -9,10-dihydroanthracene)]PF6, [9]PF6, in 4:1 molar ratio at 295 K in CD2Cl2, in which the endomethylene protons of the COD ligand and the agostic hydride in [9]PF6 exchange rapidly on the NMR time scale, even at 193 K. Thermodynamic parameters for the equilibrium between [8]PF6 and [9]PF6 in acetone-d6 have been derived from variable-temperature NMR experiments; ΔH° = -12 ± 1 kJ mol-1, ΔG° = 1 ± 2 kJ mol-1, and ΔS° = -44 ± 4 J K-1 mol-1. The large negative entropy is consistent with the agostic formulation. As expected, the η3-cyclooctenyl complex can be trapped as [Ru(1-3-η3-C8H13)(η6-9,10-di hydroanthracene)-(CO)]PF6, [10]PF6, in 80% yield on exposure of the equilibrium mixture of [8]PF6 and [9]PF6 to an atmosphere of CO. Addition of D2O to the equilibrium mixture leads to selective facile deuteration of the hydride and endo-methylene protons of the 1,5-COD and cyclooctenyl ligands. Such endo-selective H/D exchange reaction is also observed for [5]PF6.
UR - http://www.scopus.com/inward/record.url?scp=0037482846&partnerID=8YFLogxK
U2 - 10.1021/om0205997
DO - 10.1021/om0205997
M3 - Article
SN - 0276-7333
VL - 21
SP - 5738
EP - 5745
JO - Organometallics
JF - Organometallics
IS - 26
ER -