title: Diametrically opposite trends in alkene insertion in late and early transition metal compounds: relevance to transition-metal-catalyzed polymerization of polar vinyl monomers.
abstract: Variable-temperature 1H NMR studies of the reaction of cationic (alpha-diimine)Pd-alkyl complexes with alkenes are presented. The studies reveal that vinyl bromide coordinates to the Pd(II)-Me complex followed by migratory insertion and beta-bromo elimination, to generate free propene. Propene further reacts to give beta-agostic Pd(II)-tert-butyl species. From the reactions with vinyl bromide, stable chloro-bridged dicationic Pd complex was isolated and characterized. For a series of alkenes (CH2=CHX), the rate for migratory insertion decreases as follows: X = CO2Me > Br > H > Me.
authors.affiliation: Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.
authors.forename: Myeongsoon
authors.initials: M
authors.lastname: Kang
authors.forename: Ayusman
authors.initials: A
authors.lastname: Sen
authors.forename: Lev
authors.initials: L
authors.lastname: Zakharov
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold