C−C and C−H Bond Activation at Ruthenium(II):  The Stepwise Degradation of a Neopentyl Ligand to a Trimethylenemethane Ligand

Abstract

Ruthenacyclobutane complexes (SiP3)(PMe3)Ru(CH2EMe2CH2) (SiP3 = MeSi(CH2PMe2)3; 1, E = C; 2, E = Si) were synthesized from (SiP3)(PMe3)RuCl2 (3) and 2 equiv of the Grignard reagents, Me3ECH2MgCl. Metallacycle 1 was found to reversibly interconvert with the allyl complex (SiP3)Ru(Me)(η3-CH2CMeCH2) (4) and PMe3 when heated above 75 °C. From the results of kinetic studies and thermolysis of labeled material, the interconversion is proposed to take place by reversible β-methyl elimination/insertion. Conversion of 1 to 4 is an endothermic process (ΔH° = 14.3 ± 1.1 kcal mol-1), but it is entropically favorable (ΔS° = 40.9 ± 2.8 cal K-1 mol-1) due to the loss of the PMe3 ligand. Activation parameters for the β-insertion were determined to be ΔH ⧧ = 26.0 ± 1.2 kcal mol-1 and ΔS ⧧ = −10.5 ± 0.9 cal K-1 mol-1. Allyl complex 4 has been isolated as a mixture of isomers (7:1 endo:exo). The mechanism of interconversion of 4 endo and 4 exo was determined by 1H{31P} NMR spectroscopy (EXSY) to be a process involving a stereochemically rigid, square-pyramidal η1-intermediate. Thermolysis of 4 leads to loss of CH4 and the production of the trimethylenemethane complex (SiP3)Ru(η4-C(CH2)3) (7). The solid state structures of 1 and 7 were determined by X-ray diffraction.

Organometallic Chemistry of Ga+: Formation of an Unusual Gallium Dimer in the Coordination Sphere of Ruthenium

“…This value matches well with the data of most other TMM complexes. [22,23] The Ru À Ga bond length averages to 2.348 , which is relatively short, but still in line with known Ru II À GaCp* complexes that also show symmetrically h 5 -coordinated Cp* ligands at the Ga centre. [16,19] The preparation of the second test complex, the Ru II hydride,…”

Synthesis and Characterization of Pentaphosphino Zero-Valent Iron Complexes and Their Corresponding Iron(II)-Chloride and -Hydride Complexes

“…Small volumes of methanol, tert-butyl alcohol, indene, and ethyl acetate were degassed and stored over 4 Å molecular sieves. Tris(dimethylphosphinomethyl)-methylsilane (SiP 3 ) 52 and [(SiP 3 Fe) 2 (μ-Cl) 3 ] [Cl] 19 were prepared according to literature procedures. 1 H nuclear magnetic resonance (NMR) spectra were obtained on Varian Inova 300 MHz and Varian Unity Plus 400 MHz instruments.…”

Bis(acetylido) Complexes of Ruthenium(II) Bearing Monodentate Phosphane Ligands

“…Terminal acetylenes were purchased from Aldrich and used as received. cisRuMe 2 (PMe 3 ) 4 (1) was prepared from trans-RuCl 2 (PMe 3 ) 4 [34] and Me 2 Mg in thf. The NMR spectra of this complex corresponded with that reported in the literature.…”