Title
Silica-Supported Organolanthanum Catalysts for C–O Bond Cleavage in Epoxides
Publication Date
2-12-2020
Department
Ames Laboratory; Chemistry
Campus Units
Ames Laboratory, Chemistry
OSTI ID+
1601279
Report Number
IS-J 10158
DOI
10.1021/jacs.9b11606
Journal Title
Journal of the American Chemical Society
Volume Number
142
Issue Number
6
First Page
2935
Last Page
2947
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.
DOE Contract Number(s)
AC02-07CH11358
Language
en
Publisher
Iowa State University Digital Repository, Ames IA (United States)
Supporting Information
