title: Well-defined silica-supported rare-earth silylamides.
abstract: Rare-earth silylamides [Ln{N(SiMe3)2}3] [1a-d, Ln = Y (1a), La (1b), Nd (1c), Sm (1d)] react with partially dehydroxylated silica to generate the singly surface-bonded species [(Si-O)Ln{N(SiMe3)2}2] (2a-d). Trimethylsilylation of silanols occurs during the grafting process, affording in fine a hydroxyl-free surface. Contacting these well-defined surface species with excess triphenylphosphine oxide yields [(Si-O)Ln{N(SiMe3)2}2(OPPh3)] surface adducts 3a-d as the major (80%) species, leaving about 20% of unreacted siloxide bisamido species (20%). In addition to elemental analysis and infrared spectroscopy, solid-state NMR spectroscopy was used to characterize these new materials and proved to be a particularly efficient tool for the study of the paramagnetic Nd- and Sm-containing materials and for providing unambiguous verification of OPPh3 coordination on the rare-earth center. Silica-supported rare-earth amides 2a-d are active catalysts for 1-hexene and styrene hydrosilylation and for phenylacetylene dimerization. When compared to the molecular species 1a-d, grafting of the catalyst induces significant changes in the activity and selectivity of these systems.
authors.affiliation: Unité de Catalyse et de Chimie du Solide UMR 8181 CNRS, ENSCL, BP 90108, 59652 Villeneuve d'Ascq Cedex, France. regis.gauvin@ensc-lille.fr
authors.forename: Régis M
authors.initials: RM
authors.lastname: Gauvin
authors.forename: Laurent
authors.initials: L
authors.lastname: Delevoye
authors.forename: Rahma Ali
authors.initials: RA
authors.lastname: Hassan
authors.forename: Jérôme
authors.initials: J
authors.lastname: Keldenich
authors.forename: André
authors.initials: A
authors.lastname: Mortreux