title: Polyphosphazenes for the Stille reaction: a new type of recyclable stannyl reagent.
abstract: A random phosphazene copolymer {[N = P((CH2)7-Br)Ph]0.5[N = PMePh]0.5}n (2) and a block copolyphosphazene {[N = P((CH2)7-Br)Ph]0.5[N = PMePh]0.5}45-b-[N = P(O2C12H8)]55 (5), having a branch with two randomly distributed units, have been synthesized and used as precursors for the stannyl derivatives {[N = P((CH2)7-SnBu2An)Ph]0.5[N = PMePh]0.5}n (3) and {[N = P((CH2)7-SnBu2An)Ph]0.5[N = PMePh]0.5}45-b-[N = P(O2C12H8)]55 (6, An = p-MeOC6H4). Polymers 3 and 6 were tested as recyclable tin reagents in the Stille cross-coupling reaction with ArI, using various Pd catalysts and different experimental conditions. Polymer 6 can be recycled without a significant release of tin, but its efficiency decreased after three consecutive cycles. This effect was explained by studying the self-assembly of the polymer under the same conditions used for the catalytic experiments, which evidenced the progressive coalescence of the polymeric vesicles (polymersomes) leading to stable and bigger core-shell aggregates by the attraction of the [N = P(O2C12H8)] rich membranes, thus decreasing the accessibility of the tin active centers.
authors.affiliation: IU CINQUIMA/Química Inorgánica, Universidad de Valladolid, 47071-Valladolid, Spain. albeniz@qi.uva.es.
authors.forename: Sheila
authors.initials: S
authors.lastname: Martínez-Arranz
authors.forename: David
authors.initials: D
authors.lastname: Presa-Soto
authors.forename: Gabino A
authors.initials: GA
authors.lastname: Carriedo
authors.forename: Alejandro
authors.initials: A
authors.lastname: Presa Soto
authors.forename: Ana C
authors.initials: AC
authors.lastname: Albéniz