34692-09-6Relevant articles and documents
ALKYL-, ALKENYL- UND HYDRIDO-OLEFIN-KOMPLEXE DES RUTHENIUMS
Lehmkuhl, Herbert,Grundke, Juergen,Benn, Reinhard,Schroth, Gerhard,Mynott, Richard
, p. C5 - C8 (1981)
Cp(PPh3)2Ru-prim.alkyl complexes 2-6 and the η1-alkenylruthenium compound 7 have been prepared by treatment of the corresponding chlororuthenium compound 1 with the appropriate organomagnesium halides.Magnesium compounds with sec.- or tert.-alkyl groups afford the hydrido-Ru-complex 8 via olefin elimination.At 80 deg C 3-5 eliminate one PPh3 and are converted into the hydridoolefin-complexes 9-11.Stable Cp(PPh3)Ru-η1,η2-4-alkenyl complexes 14 and 15 are obtained if β-H-elimination is prevented by trans configuration of Ru and β-H in a cyclopropyl system.
Addition of catecholborane to a ruthenium-alkyl: Evidence for σ-bond metathesis with a low-valent, late transition metal
Hartwig, John F.,Bhandari, Sonali,Rablen, Paul R.
, p. 1839 - 1844 (2007/10/02)
Addition of catecholborane to the low-valent CpRu(PPh3)2Me complex led to formation of the corresponding ruthenium hydride and methylcatecholborane by a mechanism more characteristic of high-valent metal centers. Kinetic experiments conclusively showed that oxidative addition of the B-H bond did not occur. A stereochemical analysis of the reaction employing, (R,R)- and (R,S)-CpRu(DPPP)Me (DPPP = 1,2-bis(diphenylphosphino)propane) showed that epimerization of the ruthenium center was occurring before product formation and that the species undergoing epimerization never reformed starting material. The exchange reaction, therefore, involved an intermediate whose formation was rate determining. The observation of a primary deuterium isotope effect (1.62±0.13) and the absence of exchange between CpRu(PPh3)Me-d3 and MeBcat provided strong evidence for weakening of the borane B-H bond during formation of the transition state leading to this intermediate. The electronic effect of varying the phosphine ligand suggested a buildup of positive charge at the metal center, consistent with an intermediate possessing a coordinated hydridoborate ligand. All of the data were consistent with a mechanism proceeding through a four-centered transition state that involves partial cleavage of the B-H bond during formation of the B-C bond. Epimerization occurred by dissociation of the resulting hydridoborate ligand to form a three-coordinate ruthenium cation. The intermediate resulting from this step was trapped as a THF complex of the cationic ruthenium center during reactions in this solvent. The unligated three-coordinate cation provided epimerized product, but was not on the pathway to exchange of the boron-hydrogen and ruthenium-methyl groups.
Alkylruthenium(II) Compounds and their β-H-Elimination into (η2-Alkene)hydridoruthenium Complexes
Lehmkuhl, Herbert,Grundke, Juergen,Mynott, Richard
, p. 159 - 175 (2007/10/02)
Reaction of Cp(PPh3)2RuCl (1) with primary alkylmagnesium halides (alkyl = Et, Pr, n-Bu, i-Bu) leads to the corresponding alkylruthenium complexes 4 - 7.Above 50 deg C 4 - 7 lose a PPh3 molecule and form by Ru-β-H-elimination the (η2-alkene)hydridoruthenium complexes 9 - 12.With R = isobutyl the intermediately formed, coordinatively unsaturated Cp(PPh3)Ru - R commplex can be stabilized by complexation with ethylene (50 bar) as (η2-ethylene)isobutylruthenium complex 15.Mechanistic investigations of the ethyl complex 16 indicate that the Ru-β-H-elimination is reversible. - Rotation of the η2-alkene ligand in 9 - 12 leads to temperature-dependent 1H NMR spectra.The 31P chemical shifts of 1,2,4 - 7 and 9 - 12, respectively, are characteristic for the corresponding type of complexes.
