Tris[p-(N-oxyl-N-tert-butylamino)phenyl]amine, -methyl, and -borane Have Doublet, Triplet, and Doublet Ground States, Respectively
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- 作者：Tetsuji Itoh ; Kenji Matsuda ; Hiizu Iwamura ; and Kenzi Hori
- 刊名：Journal of the American Chemical Society
- 出版年：2000
- 出版时间：March 22, 2000
- 年：2000
- 卷：122
- 期：11
- 页码：2567 - 2576
- 全文大小：194K
- 年卷期：v.122,no.11(March 22, 2000)
- ISSN：1520-5126
文摘
N,N,N-Tris[p-(N-oxyl-tert-butylamino)phenyl]amine (N) was obtained as dark violet plates bylithiation of tris(4-bromophenyl)amine, followed by reaction with 2-methyl-2-nitrosopropane and oxidation ofthe resulting tris(hydroxyamine) with Ag2O. An X-ray crystal and molecular structure analysis of the monoclinicsingle crystal with space group Cc showed that it has neither C3 symmetry nor zwitterionic quinonoid structure.An EPR spectrum in MTHF solution at room temperature consisted of seven lines (aN = 4.06 G (3N) at g =2.0058). The temperature dependence of the magnetic susceptibility data on N in the range 2-300 K wasanalyzed in terms of a triangular coupling model for three S = 1/2 spins to give a set of best-fit parameterswhich placed a doublet state as the ground state with a quartet state lying 559 K (= 1.11 kcal mol-1) aboveit. B3LYP/6-31G*//B3LYP/6-31G computations were performed on both spin states of a model molecule (N')in which all three N-tert-butyl groups in N were replaced with N-methyl groups. The doublet state was foundto be more stable than the quartet state by 0.84 kcal mol-1. Tris[p-(N-oxyl-tert-butylamino)phenyl]methyl (C)gave a monoclinic single crystal with space group Cc (no. 9) and has been shown to have a benzoquinoneimineN-oxide type diradical structure. Temperature dependence of its magnetic susceptibility showed that C has atriplet ground state with a singlet state lying 410 K above the triplet. Reactions of the correspondingorganolithium compounds with BF3·OEt2 were not applicable to give tris[4-(N-oxyl-tert-butylamino)phenyl]borane (B) but its 2,2',2' ',6,6',6' '-hexamethyl derivative (B'). In the trigonal crystal with space group R
(no.148), the three benzene rings are tilted by 49.2
with respect to the valence plane of the boron atom. Themagnetic susceptibility data on B' were consistent with a doublet ground state with an energy gap to a quartetstate by 9.9 K (= 0.0197 kcal mol-1). All the results together with ab initio MO studies are consistent witha picture that the ground spin states of title compounds N, C, and B are doublet, triplet, and doublet, respectively.The electronic structures are explained qualitatively by p-(N-oxyl-tert-butylamino)phenyl homologues of(
H2C)3X in which X = N, C·, and B atoms, and two, one, and no 
-electrons are contained, respectively.
(no.148), the three benzene rings are tilted by 49.2 with respect to the valence plane of the boron atom. Themagnetic susceptibility data on B' were consistent with a doublet ground state with an energy gap to a quartetstate by 9.9 K (= 0.0197 kcal mol-1). All the results together with ab initio MO studies are consistent witha picture that the ground spin states of title compounds N, C, and B are doublet, triplet, and doublet, respectively.The electronic structures are explained qualitatively by p-(N-oxyl-tert-butylamino)phenyl homologues of(H2C)3X in which X = N, C·, and B atoms, and two, one, and no -electrons are contained, respectively.