Cis-catalysts

Figure 9. TEM images of the PtpC)/SBA-15-CI catalysts. X = (a) 1.7nm, (b) 2.6nm, (c) 2.9nm, (d) 3.6nm, and (e) 7.1 nm. The scale bars represent 20nm [13]. (Reprinted from Ref [13], 2005, with permission from American Chemical Society.)...

Figure 6.9 Descriptors calculated for phosphines in the irons-Rh (PR3)2(CO)CI catalyst a the deformation coordinate S4 is employed as steric measure b stereo-electronic map showingthe distribution of the various PR3 ligands.

A complementary approach to the synthesis (1R,2S)-1 has been developed by Merck using (.S, .S )-Mnl.CI catalyst in a hypochlorite medium to provide (IS, 2/0-indene oxide 26. This intermediate was converted without isolation to r/.v-aminoindanol in a stereoselective and regioselective manner using Ritter technology (Scheme 24.2). Several key issues, detailed later in this chapter, have been addressed and resolved in both Jacobsen s AE52 and Ritter technology50 to develop a reproducible and practical large-scale process for the synthesis of enantiopure d.s-aminoindanol. 

With [Ni(C3H5)I]2 as a trans catalyst and [Ni(C3H5)02CF3]2 as a cis catalyst the allyl insertion mechanism has been proven directly by H- and C-NMR spectroscopic measurements as the principle catalytic reaction for chain growth in diene polymerization [24, 25] (cf. Scheme 2). 

Finally the effect of Pt-Re interactions on sulfur adsorption and on coke deposition on the different Pt-Re/AI2O3-CI catalysts was investigated. The toxicity of these poisons was evaluated with regards to a pure metallic reaction, in this case dehydrogenation of cyclohexane. 

Figure 11. Asymmetric (Ci) catalyst precursors for the synthesis of hemiisotactic polymers.

Rieger has recently reported another class of Ci catalysts (45) for the synthesis of stereoblock polypropylenes. However unlike the polymers formed using 42—44, polymers ranging from flexible plastics (with melting points as high as 134 °C) to thermoplastic elastomers are produced. Similar metallocenes... 

Apesteguia, C.R., Garetto, T.F., Borgna, A. (1987). On the Sulfur-Aided Metal-Support Interaction in Pt/ AI2O3-CI Catalysts. Journal of Catalysis, V0I.IO6, No.l, (July 1987),... 

Nickel Catalysts. The use of a Lewis base to convert an otherwise cis catalyst into a trans catalyst has already been demonstrated for nickel (212-214). Similarly, the cis-specific nickel catalyst can also be converted into a trans catalyst by replacing Ni-F complexes with Ni-I. Polymers obtained from these systems can have up to 97% trans content (262). 

To rationalize these results, a conformational study of these peptidomimetics was undertaken. DKP scaffolds can induce a well-defined tridimensional stracture and the importance of this characteristic was proven in several studies [20]. In fact, as a consequence of the absolute configuration of the two a-amino acids forming the cyclic dipeptide unit, the two reachve functionalities (amino and carboxylic acid) are locked in a cis- (catalysts 7 and 8) or trans[Pg.104]

Rh(S,S-Me-DuPHOS)(hepla-2,5-diene)CI catalyst formed in stfufrom Rh(S,S-MeDuPHOS)(ndb) SbF5 under H2 gas. 

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