Heats of reaction of pyridine, triphenylphosphine, and triphenyl phosphite with the chloro-, bromo-, and iodo-1,5-cyclooctadienerhodium(I) dimers and dichlorobis(benzonitrile)palladium(II)

Partenheimer, Walter,Hoy, Edgar F.

, p. 2805 - 2809 (1973)

The heats for the following reactions in dichloromethane are reported: [RhX(COD)]2 + 2B → 2[RhX(COD)(B)]; [RhX(P-(OC6H5)3)2]2 + 2P(OC6H5)3 → 2[RhX(P(OC6H5)3)3]; [RhX(COD)2] + 2P(OC6H5)3 → [Rh2X2(COD)(P(OC6H5) 3)2] + COD; [Rh2X2(COD)(P(OC6H5) 3)2] + 2P(OC6H5)3 → [RhX(P(OC6H5)3)2]2 + COD; [PdCl2(C6H5CN)2] + 2B → [PdCl2B2] + 2C6H5CN; and [PdCl2(COD)] + 2P(OC6H5)3 → [PdCl2(P(OC6H5)3)2] + COD (B = pyridine, triphenylphosphine; X = Cl, Br, I; COD = 1,5-cyclooctadiene). Relative displacement energies are for the rhodium compounds, triphenyl phosphite ? 1,5-cyclooctadiene and triphenylphosphine > pyridine, and for the palladium compounds, triphenylphosphine > triphenyl phosphite > pyridine ? cyclooctadiene. Arguments are given that solvent-solute enthalpic contributions are not predominant in the displacement energies. For a given reaction, the effect of varying the halogens upon the observed enthalpies is very small or nonexistent. Equilibrium constants for the first reaction are too high to measure when B = triphenylphosphine and are approximately 5 × 104 when B = pyridine.

Partenheimer, W.,Hoy, E. F.

, p. 2840 - 2845 (1973)

Regioselectivity in the rhodium catalysed 1,4-hydrosilylation of isoprene. Aspects on reaction conditions and ligands

Gustafsson, Magnus,Frejd, Torbj?rn

, p. 438 - 443 (2007/10/03)

The regioselectivity in the Rh catalysed 1,4-hydrosilylation of isoprene was investigated. Variation of solvents and temperature did not significantly affect the isomer distribution between tail-product (I) and head-product (II). The choice of ligands had

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.