24651-65-8Relevant articles and documents
HRh4 as a hydrogenation and isomerization catalyst
Coolen, H.K.A.C.,Nolte, R.J.M.,Leeuwen, P.W.N.M.
, p. 159 - 168 (1995)
The preparation and reactions of 4> (2) have been investigated.The metallation product 3> (4) has been characterized by 31P NMR spectroscopy.Catalytic hydrogenation of alkenes with 2 depends strongly on the amount of extra ligand added and the substrate (1-hexene, Z,E-2-hexene and allylbenzene).Without added phosphite, traces of 2)2> are the actual catalyst.Under these conditions the reaction is zero order in substrate.The kinetics are completely different when extra triphenyl phosphite is present.Complex 2 behaves as a catalyst with a character in between that of ClRh(PPh3)3 and cationic Rh(diphosphine)+. Keywords: Rhodium; Hydrogenation catalyst; Isomerization catalyst
New insight into role of ortho-metallation in rhodium triphenylphosphite complexes. Hydrogen mobility in hydrogenation and isomerization of unsaturated substrates
Trzeciak, Anna M.,Ziólkowski, Józef J.
, p. 69 - 76 (2007/10/03)
The hydrogen transfer from two rhodium(I) hydrido complexes HRh{P(OPh)3}4 and HRh(CO){P(OPh)3}3 to methyl acrylate and/or allylbenzene leads to the formation of ortho-metallated complexes Rh{P(OC6H4)(OPh)2}{P(OPh)3} 3 (I) and Rh{P(OC6H4)(OPh)2}(CO){P(OPh)3} 2 (II), respectively. During these reactions unsaturated substrates, methyl acrylate or allylbenzene undergo stoichiometric hydrogenation. A similar reaction was also observed for HRh{P(OR)3}4 complexes (R=3-CH3C6H4, 4-CH3C6H4). The complex HRh{P(OPh)3}4 catalyses the isomerization of hex-1-ene to hex-2-ene in the absence of H2; however at 1 atm of H2 the formation of hexane is observed. Hydrido complexes of the type HRh{P(OR)3}4 in D2 atmosphere undergo H/D exchange at the ortho position of coordinated triarylphosphite. Deuteration of the ortho protons in complexes with R=Ph, 3,5-(CH3)2C6H3 and 4-CH3C6H4 is total, whereas only one ortho hydrogen is replaced in the case of R=3-CH3C6H4. The formation of an ortho-metallated chelating ring causes a downfield shift in the 1H-NMR signal of one proton from the phenyl ring to δ ca. 8 ppm.
