17084-20-7Relevant academic research and scientific papers
Kinetic and thermodynamic stabilities of the geometric isomers of (R3P)2Ru(CO)2Cl2 and (R3P)3Ru(CO)Cl2 complexes
Krassowski, Daniel W.,Nelson, John H.,Brower, Kay R.,Hauenstein, Dale,Jacobson, Robert A.
, p. 4294 - 4307 (2008/10/08)
A series of ruthenium(II) complexes of the type RuCl2(CO)2P2 (P = Bzl3P, Ph3P, Ph2MeP, PhMe2P, Me3P) have been prepared and characterized by elemental analyses, physical properties, infrared spectroscopy, UV-visible spectroscopy, and 1H, 13C{1H} and 31P{1H} NMR spectroscopy. The first-formed complex, with all ligand pairs trans (ttt), thermally isomerizes in solution to produce the isomer with all ligand pairs cis (ccc). This ccc isomer further isomerizes in solution to produce the thermodynamically preferred isomer with only the phosphine ligands trans (cct). The size and basicity of the phosphine affect the isomerization rate, which increases with an increase in size and a decrease in phosphine basicity and proceeds by initial dissociation of carbon monoxide. Activation parameters, ΔS? and ΔV?, are both positive for the ttt-ccc isomerization consistent with a dissociative process. Negative values of ΔS? for the ccc → cct isomerization suggest that an associative step may be important, cis- and trans-RuCl2(CO)P3 complexes with meridionally coordinated phosphines (P = Me3P, PhMe2P, Ph2MeP) were also prepared and characterized by the same methods. The first-formed isomer with trans chlorides thermally isomerizes in solution to the thermodynamically stable isomer with cis chlorides. Positive values of both ΔS? and ΔV? are consistent with a dissociative process. Phosphine inhibition of this isomerization indicates initial phosphine dissociation. The crystal structures of cis(1)- and trans-RuCl2(CO)(Ph2MeP)3 (1 and 2, respectively) have been determined by counter methods. Compound 1 crystallizes in space group P1 with a = 16.158 (4) A?, b = 18.361 (3) A?, c = 13.170 (4) A?, α = 93.36 (2)°, β = 108.03 (3)°, γ = 90.75 (2)°, and Z = 4. Compound 2 crystallizes in space group P21/c with a = 20.373 (9) A?, b = 9.831 (5) A?, c = 20.689 (7) A?, β = 117.43 (3)°, and Z = 4. Both structures were refined by least-squares methods with R = 0.093 for 1 and R = 0.069 for 2 for 4614 and 2974 unique reflections with I/σ(I) ≥ 3.0 for 1 and 2, respectively. The bond distance of the phosphine trans to carbon monoxide in the trans isomer (d(RuP) = 2.490 (4) A?) is longer than the other two Ru-P distances (2.403 (4) A?). The 31P{1H} NMR data also suggest that this phosphine is relatively weakly bound and so this phosphine likely dissociates as the first step in the geometric isomerization.
