Cooling system Coordinative catalysts

For catalyst recyclability, PEG6000-(TEMPO)2/CuC1 is solidified by cooling the resultants, followed by addition of diethyl ether, and thus recovers by simple filtration, and the catalytic system retains excellent catalytic performance after three runs. The presence of base (1-methylimidazole) is crucial for the oxidation of alcohols, which could deprotonate the alcohol and coordinate to Cu [65-67]. 

Figure 8 illustrates the first of a series of NMR spectra of the system reacting with ethylene. The sample was reacted for 70 min at 258 K and then cooled rapidly to 213 K and measured. The enlargement in Fig. 8 shows that the first insertion steps occurred into the Ti-C bond, as indicated by the peaks of the p-carbons of Ti-propyl and Ti-pentyl. The ethylene signal at 123 ppm (not visible in Fig. 8) remains a sharp singlet and is unshifted, demonstrating that even at the chosen ratio Ti/Al/C2H4 = 1.0 0.95 0.7 no interaction with the catalyst is detectible. Thus, pre-coordination of the monomer to the primary complex (for instance, the jt-complex of Cossee [20, 21]) is not observed and can be present only to a very minor extent. 

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