161995-39-7Relevant academic research and scientific papers
π-Stabilized, yet reactive, half-sandwich Cp*Ru(PR3)X compounds: Synthesis, structure, and bonding
Johnson, Todd J.,Folting, Kirsten,Streib, William E.,Martin, James D.,Huffman, John C.,Jackson, Sarah A.,Eisenstein, Odile,Caulton, Kenneth G.
, p. 488 - 499 (2008/10/08)
The compounds Cp*RuLX (L = PiPr2Ph, PCy3; X = Cl, Br, I, OCH2CF3, OSiPh3, OSiMe2Ph, NHPh), as well as their CO adducts, have been studied by NMR, IR, and X-ray diffraction in order to understand the nature of the Ru-X bond. Adducts were also formed with C2H4. Cp*Ru(PiPr2Ph)(OCH2CF3) reacts with MeI (but not PhI) to give Cp*Ru(PiPr2Ph)I and MeOCH2CF3. The compounds Cp*RuLX have a mirror-symmetric structure with Ru, L, X, and the Cp* center coplanar. This is understood, using extended Hückel calculations, to originate in the presence of a Ru-X partial π bond which raises the LUMO. This increases the HOMO-LUMO gap and thus disfavors pyramidalization at the metal center. Calculations of the behavior of systems with X = pure σ donor, π donor, and π acceptor support this analysis. The LUMO of Cp*RuLX still lies low enough to give visible color and to allow rapid addition of (small) Lewis bases. The v(CO) values of the CO adducts show the X ligand donor power to vary in the order OSiMe2Ph > NHPh > OSiPh3 > OCH2CF3 ? Cl > Br > I. Comparison of the Ru-X bond lengthening upon addition of CO is also consistent with this ranking. The lack of facile β-hydrogen migration when X = OCH2CF3 is discussed. Crystallographic data: for Cp*Ru(PCy3)(OSiPh3) at -160°C, a = 12.131(2) ?, b = 17.563(3) ?, c = 10.703(2) ?, α = 102.59(1)°, β = 110.02(1)°, γ = 75.87(1)° with Z = 2 in space group P1; for Cp*Ru(PCy3)CO(OSiPh3) at -178°C, a = 11.331(3) ?, b = 17.840(4) ?, c = 21.813(5) ?, and β = 97.53(1)° with Z = 4 in space group P21/n; for Cp*RuI(PiPr2Ph) at -172°C, a = 8.907(1) ?, b = 15.205(2) ?, c = 17.065(2) ?, and β= 100.62(1)° with Z = 4 in space group P21/n; for Cp*Ru(PCy3)(OCH2CF3) at -173°C, a = 12.640(3) ?, b = 14.140(3) ?, c = 17.271(4) ?, and β = 101.79(1)° with Z = 4 in space group P21/c; for Cp+Ru(PCy3)CO(OCH2CF3) at -172°C, a = 9.607(2) ?, b = 19.704(3) ?, c = 16.370(3) ?, and β = 96.55(1)° with Z = 4 in space group P21/c.
