Published in

American Chemical Society, Journal of the American Chemical Society, 47(135), p. 17943-17951, 2013

DOI: 10.1021/ja407902g

Links

Tools

Export citation

Search in Google Scholar

Bipodal Surface Organometallic Complexes with Surface N-Donor Ligands and Application to the Catalytic Cleavage of C–H and C–C Bonds in n-Butane

This paper is available in a repository.
This paper is available in a repository.

Full text: Download

Red circle
Preprint: archiving forbidden
Orange circle
Postprint: archiving restricted
Red circle
Published version: archiving forbidden
Data provided by SHERPA/RoMEO

Abstract

We present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [( Si-NH2)( Si-OH)] (1) and [( Si-NH2)(2)] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [( Si-NH-)( Si-O-)]Zr-(CH(2)tBu)(2) (3) and [( Si-NH-)(2)]Zr(CH(2)tBu)(2) (4) have been obtained by reaction with Zr(CH(2)tBu)(4). The surfaces were characterized with 2D multiple-quantum H-1-H-1 NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH(2)tBu)(4) reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 degrees C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [( Si-NH-)(2)]Zr(H)(2) (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [( Si-NH-)(2)(Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an H-1 NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [( Si-N=)( Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [( Si-NH-) ( Si-O-)]Zr(H)(2) (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [( Si-NH-)( Si-O-)(2)]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N].