Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

7-8-2009

Journal or Book Title

Inorganic Chemistry

Volume

48

Issue

16

First Page

8020

Last Page

8029

DOI

10.1021/ic900689k

Abstract

Ligand substitution reactions and catalytic hydroamination/cyclization of aminoalkenes have been studied with a new oxazolinylborato yttrium compound, tris(4,4-dimethyl-2-oxazolinyl)phenylborato bis(trimethylsilylmethyl)yttrium ([Y(κ3-ToM)(CH2SiMe3)2(THF)], 1). THF exchange in 1 is rapid at room temperature, and activation parameters obtained by simulation of 1H NMR spectra acquired from 190 to 280 K are consistent with a dissociative mechanism (ΔS‡ = 30 ± 1 e.u., ΔG‡ = 11.9 kcal mol−1 at 243 K). The related phosphine oxide adduct [Y(κ3-ToM)(CH2SiMe3)2(OPPh3)] (2) also undergoes exchange via OPPh3 dissociation with a much higher barrier (ΔG‡ = 15.0 kcal mol−1 at 320 K). Compound 1 reacts with the amines tBuNH2, para-MeC6H4NH2, and 2,6-iPr2C6H3NH2 to provide six-coordinate [Y(κ3-ToM)(NHR)2(THF)] (3: R = tBu; 4: R = para-MeC6H4) and five-coordinate [Y(κ3-ToM)(NH-2,6-iPr2C6H3)2] (6). These oxazolinylborato yttrium compounds are precatalysts for the cyclization of aminoalkenes; the kinetics of catalytic conversion indicate zero-order substrate dependence and first-order catalyst dependence. Kinetic investigations of ligand exchange processes and hydroamination reactions indicate that the tris(oxazolinyl)borato-yttrium interaction is robust even in the presence of excess phosphine oxide and primary and secondary amines.

Comments

Reprinted (adapted) with permission from Inorganic Chemistry 48 (2009): 8020, doi:10.1021/ic900689k . Copyright 2009 American Chemical Society.

Language

en

File Format

application/pdf

Included in

Chemistry Commons

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