79792-60-2Relevant academic research and scientific papers
Neighboring Group Participation of Halo and Aryl Groups in the Stoichiometric and Catalytic Reactions of Olefins with Transition-Metal Hydrides and a New Route to Arene Complexes
Crabtree, Robert H.,Mellea, Michelle F.,Quirk, Jennifer M.
, p. 2913 - 2917 (2007/10/02)
BF4 (1) reacts with ArCH=CH2 to give 6-ArEt)L2>BF4 (2, Ar=Ph, 2,6-Me2C6H3, p-MeOC6H4, PhCH2, Ph(CH2)2, 2,6-Cl2C6H3, and 2-XC6H4 ).For the first three substrates, a neighboring group participation of the aryl group via an η3-benzyl intermediate is proposed.For the next two, isomerisation takes place to give a styrene derivative which then reacts as above.For the halogen-containing substrates the unusual intermediates 3-XC6H4CH=CH2)L2>BF4 are observed, in which the substrate chelates to the metal via the (C=C) and halo groups.These are rare examples of both a halocarbon complex and an olefin dihydrido complex.The high branched:linear isomer ratios generally observed in the hydroformylation and hydrosilation of styrene are interpreted in terms of neighboring group participation via an η3-benzyl intermediate.Halo and aryl groups are suggested as candidates for study in connection with directing effects and asymmetric induction in homogeneous catalysis.
Alkane Dehydrogenation by Iridium Complexes
Crabtree, Robert H.,Mellea, Michelle F.,Mihelcic, Jean M.,Quirk, Jennifer M.
, p. 107 - 113 (2007/10/02)
Cyclopentene reacts with IrH2S2L2+ at 40 deg C (S = H2O or acetone; L = PPh3) to give CpIrHL2+.The same product is formed cyclopentane at 80 deg C in the presence of 3,3-dimethyl-1-butene (5).Cyclooctene or cyclooctane and 5 give Ir(1,5-cyclopentadiene)L+.Evidence against colloid, radical, or carbonium mechanisms is given.We propose that this system constitutes the first example of a reversible hydrogenation of an alkane by a transition-metal complex.
Dihydrido Olefin and Solvento Complexes of Iridium and the Mechanisms of Olefin Hydrogenation and Alkane Dehydrogenation
Crabtree, Robert H.,Demou, Peter C.,Eden, Don,Mihelcic, Jean M.,Parnell, Charles A.,et al.
, p. 6994 - 7001 (2007/10/02)
Tests for homogeneity are applied to the catalysts L2>A/CH2Cl2/H2 (cod-1,5-cyclooctadiene; A = BF4; L=PPh3, PMePh2) and their possible generality is discussed. L2>A (L=PPh3) reacts with H2 and S (S=solvent) to give the isolable complexes IrH2S2L2>A (1) in which the displacement order of the M-S groups is H2O ca.THF2L2>A (ol = C2H4, C3H8) and L2>A (ol = PhCH=CH2, C5H8, t-BuCH=CH2).Their role in hydrogenation is discussed in the light of stepwise catalytic 1H NMR studies at -80 to +25 deg C, in which they appear to be intermediates in catalysis.A catalytic cycle is proposed.Selectivity in competitive experiments is discussed.The rhodium analogues do no exhibit similar properties.
