DIRECT STUDIES OF 1,1-DIAZENES - SYNTHESES, INFRARED AND ELECTRONIC-SPECTRA, AND KINETICS OF THE THERMAL-DECOMPOSITION OF N-(2,2,6,6-TETRAMETHYLPIPERIDYL)NITRENE AND N-(2,2,5,5-TETRAMETHYLPYRROLIDYL)NITRENE
DIRECT STUDIES OF 1,1-DIAZENES - SYNTHESES, INFRARED AND ELECTRONIC-SPECTRA, AND KINETICS OF THE THERMAL-DECOMPOSITION OF N-(2,2,6,6-TETRAMETHYLPIPERIDYL)NITRENE AND N-(2,2,5,5-TETRAMETHYLPYRROLIDYL)NITRENE
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DOI：
10.1021/ja00367a020
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发表时间：
1982-01-01
影响因子：
15
通讯作者：
DERVAN, PB
中科院分区：
文献类型：
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作者：
HINSBERG, WD;SCHULTZ, PG;DERVAN, PB
本文报道了稳定的1，1-二氮烯Ar-（2，2，6，6-四甲基哌啶基）氮烯（4）和Ar-（2，2，5，5-四甲基吡咯烷基）氮烯（5）的合成、直接光谱观察和热分解动力学。4在-78 ℃下的电子吸收光谱揭示了n，ir* 跃迁的结构吸收：在Et 2 O中，Xmax= 543 nm，X 0，0= 620 nm，和emax= 18±3;在CH 2Cl 2中，Xmax= 541 nm，X 0，0 = 610 nm;在i-PrOH中，Xmax= 526 nm，和X 0，0 = 592 nm。1，1-二氮烯5在-78 ℃下的电子吸收光谱显示了一个结构化的n，ir* 跃迁吸收带：在CH_2Cl_2中，Xmax= 497 nm，Xq_0 = 572 nm，tmax= 20±3;在f-PrOH中，Xmax= 487 nm，Xq_0 = 552 nm. 4的红外光谱在1595 cm-1（R214 N = 14 N伸缩）处显示出强吸收，并提供了1，1-二氮烯4在基态具有相当大的N= N双键特征的证据。5的红外光谱在1638 cm-1处显示出强吸收（R214 N = 14 N伸缩）。4的热分解的单分子速率对溶剂敏感，该速率随着溶剂极性的降低而增加（在THF、Et 2 O和己烷中分别为k^= 1.0、1.7、4.8）。1，1-二氮烯4的单分子断裂的活化参数如下：在己烷中log A= 11.6 ± 0.5和ε a= 16.9±0.7 kcal mol-1;在Et 2 O中log A= 13.7±0.3和ε a= 20.0±0.4 kcal mol-1;在THF中log A= 13.6±0.3和ε a= 20.1±0.4 kcal mol-1。在CDC 13中，4的双分子二聚化的活化参数为log A= 3.8±0.7和Ea = 6.4±0.9 kcal mol-1。5的单分子热分解速率对溶剂敏感，随着溶剂极性的减小，速率增大，THF、Et 2 O和己烷的kni分别为1.0、2.4和5.1。1，1-二氮烯5单分子裂解的活化参数如下：在己烷中，log A= 10.9±0.3，ε a= 16.8±0.5千卡mol ~（-1）;在Et_2O中，log A= 12.4±0.4，ε a= 19.0±0.6千卡mol ~（-1）;在THF中，log A= 12.1±0.3，ε a= 19.1±0.4千卡mol ~（-1）。在-41.1C下，5的二聚反应的双分子速率常数为8.5 X 10 '5 L/（mol s），比4的速率慢90倍。从六元环到五元环的1，1-二氮烯的变化导致n，ir* 跃迁向高能量的移动和N= N伸缩频率向增加的波数（cm ~（-1））的移动，这与等电子酮、四甲基环己酮和四甲基环戊酮的变化没有什么不同。4和5的单分子热碎裂的类似的ε a值可能表明4和5之间的应变能差也很小。1，1-二氮烯5的生成热约为30.5kcal·mol ~（-1），比顺式，2-二氮烯异构体高20 kcal·mol ~（-1）。
The syntheses, direct spectroscopic observation, and kinetics of thermaldecomposition of the persistent 1, 1-diazenes, Ar-(2, 2, 6, 6-tetramethylpiperidyl) nitrene (4) and Ar-(2, 2, 5, 5-tetramethylpyrrolidyl) nitrene (5) are reported. The electronic absorption spectrum of 4 at-78 C reveals a structured absorption for the n, ir* transition: Xmax= 543 nm, X0> 0= 620 nm, and emax= 18±3 in Et20; Xmax= 541 nm and Xoi0= 610 nm in CH2C12; Xmax= 526 nm and Xo, o= 592 nm in i-PrOH. The electronic absorption spectrum of 1, 1-diazene 5 at-78 C reveals a structured absorption band for the n, ir* transition: Xmax= 497 nm and Xqo= 572 nm and tmax= 20±3 in CH2Cl2; Xmax= 487 nm and X00= 552 nm in f-PrOH. The infrared spectrum of 4 shows a strong absorption at 1595 cm'1 (R214N= 14N stretch) and provides evidence that 1, 1-diazene 4 has considerable N= N double-bond character in the ground state. The infrared spectrum of 5 shows a strong absorption at 1638 cm'1 (R214N= 14N stretch). The unimolecular rate of thermal decomposition of 4 is sensitive to solvent, the rate increasing with decreasing solvent polarity (k^= 1.0, 1.7, 4.8 in THF, Et20, and hexane, respectively). The activation parameters for the unimolecular fragmentation of 1, 1-diazene 4 are as follows: log A= 11.6• 0.5 and£ a= 16.9±0.7 kcal mol'1 in hexane; log A= 13.7±0.3 and£ a= 20.0±0.4 kcal mol'1 inEt20; log A= 13.6±0.3 and£ a= 20.1±0.4 kcal mol'1 in THF. The activation parameters for the bimolecular dimerization of 4 are log A= 3.8±0.7 and£ a= 6.4±0.9 kcal mol'1 in CDC13. The unimolecular rate of thermal decomposition of 5 is sensitive to solvent, the rate increasing with decreasing solvent polarity, kni= 1.0, 2.4, and5.1 for THF, Et20, and hexane, respectively. The activation parameters for the unimolecular fragmentationof 1, 1-diazene 5 are as follows: log A= 10.9±0.3 and£ a= 16.8±0.5 kcal mol'1 in hexane; log A= 12.4±0.4 and£ a= 19.0±0.6 kcal mol'1 in Et20; log A= 12.1±0.3 and£ a= 19.1±0.4 kcal mol'1 inTHF. At-41.1 C the bimolecular rate constant for the dimerization of 5 is 8.5 X 10'5 L/(mol s), 90 times slower than that found for 4. The change from a six-membered to a five-membered ring 1, 1-diazene causes a shift to higherenergy for the n, ir* transition and a shift to increased wavenumber (cm'1) for the N= N stretching frequency, not unlike that of the isoelectronicketones, tetramethylcyclohexanone and tetramethylcyclopentanone. Similar£ a values for the unimolecular thermal fragmentationof 4 and 5 may indicate the strain energy difference between 4 and 5 is also small. An approximate value of 30.5 kcal mol'1 for the heat of formation of the 1, 1-diazene 5 is estimated, indicating the1, 1-diazene 5has a higher heat of formation than the c/vl, 2-diazene isomerby 20 kcal mol'1.