Campus Units

Chemistry, Ames Laboratory

Document Type

Article

Publication Version

Submitted Manuscript

Publication Date

2-12-2020

Journal or Book Title

Journal of the American Chemical Society

Volume

142

Issue

6

First Page

2935

Last Page

2947

DOI

10.1021/jacs.9b11606

Abstract

Single-site organolanthanum complexes supported on mesoporous silica nanoparticles, La{C(SiHMe2)3}n@MSNs, catalyze the ring-opening hydroboration reaction of aliphatic and styrenic epoxides with pinacolborane (HBpin). The surface-bound complexes, synthesized by reaction of the homoleptic tris(alkyl)lanthanum La{C(SiHMe2)3}3 and SBA-type MSN treated at 700 °C (MSN700), are mostly monopodal ≡SiO—La{C(SiHMe2)3}2 and contain an average of one bridging La↼H—Si per alkyl ligand. This structure was established through a combination of solid-state NMR (SSNMR) experiments, including J-resolved SiH coupling and quantitative 29Si measurements, diffuse reflectance IR, and elemental analysis. These rigorous analyses also established that grafting reactions in pentane provide a preponderance of ≡SiO—La{C(SiHMe2)3}2 sites and are superior to those in benzene and THF, and that grafting onto MSN treated at 550 °C (MSN550) results in a mixture of surface species. The single-site supported catalysts are more selective and in most cases more active than the homogeneous analogue, allow easy purification of products from the catalyst, are strongly resistant to leaching into solution phase, and may be recycled for reuse at least five times. After reaction of La{C(SiHMe2)3}n@MSN and HBpin, species including ≡SiO—La{C(SiHMe2)3}(H2Bpin) and ≡SiO—La{C(SiHMe2)3}{κ2–pinB–O(CMe2)2OBH3} are identified by detailed 1D and 2D 11B SSNMR experiments.

Comments

This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of the American Chemical Society, copyright © American Chemical Society after peer review. To access the final edited and published work see DOI: 10.1021/jacs.9b11606. Posted with permission.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

2020-SadowAaron-SilicaSupported-SI.pdf (1242 kB)
Supporting Information

Published Version

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