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A range of dialkenylmagnesium compounds ([CH2-CH(CH2)n]2Mg; n = 1-6) were synthesized and used as chain transfer agents (CTA) with either (C5Me5)2NdCl2Li(OEt2)2 (1) or [Me2Si(C13H8)2Nd(BH4)2Li(thf)]2 (2) neodymium precursors for the polymerization of ethylene. In all cases, the systems followed a controlled coordinative chain transfer polymerization mechanism. The intramolecular insertion of the vinyl group on the CTA in growing chains is possible and led to the formation of cyclopentyl, cyclohexyl, and possibly cycloheptyl chain ends. While the production of cyclopentyl- or cyclohexyl-capped polyethylene chains can be quantitative (n = 2-5), the integrity of this double bond can also be kept if n is higher than 6. In comparison to 1/CTA catalytic systems, 2/CTA catalytic systems showed a higher propensity to produce cycloalkyl chain ends. This was ascribed to the lower steric demand around the active site, as shown by DFT calculations. In addition, the formation of bis(cyclopentylmethyl)magnesium from dipentenylmagnesium using a catalytic amount of 2 was shown. [ABSTRACT FROM AUTHOR]

Di(1-(propyl)-2,2,5,5-tetramethyl-1-aza-2,5-disilacylopentane)magnesium was synthesized and used as chain transfer agent for the ethylene polymerization in the presence of a neodymocene precursor. The polymerization was shown to be governed by a catalyzed chain growth process (CCG) on magnesium, allowing the quantitative formation of ammonium or amine functionalized polyethylene (PE) chains. The structure of these chains was shown by 1H and 13C NMR analyses. MALDI-ToF mass spectrometry was successfully used to confirm the structure predicted by the CCG mechanism. The additional formation of telechelic PE chains carrying an ammonium and either a diethyldithiocarbamate or an iodo moiety as end groups was shown after a simple deactivation of the polymerization medium with disulfiram or molecular iodine, respectively. [ABSTRACT FROM AUTHOR]