Insertion reactions of phenyl isocyanate into hafnium nitrogen bonds: synthesis and reactivity of hafnium complexes bearing substituted pyrrolyl ligands
Resource
Journal of Organometallic Chemistry 689 (21): 3362-3369
Journal
Journal of Organometallic Chemistry
Journal Volume
689
Journal Issue
21
Pages
3362-3369
Date Issued
2004
Date
2004
Author(s)
Hsieh, Kun-Chun
Lee, Wen-Yi
Lai, Chun-Liang
Hu, Ching-Han
Lee, Hon Man
Huang, Jui-Hsien
Lee, Gene-Hsing
Abstract
A bis(diethylamido)hafnium compound [C4(CH2NMe 2)-2]2Hf(NEt2)2 (1) has been prepared in 79% yield by reacting Hf(NEt2)4 with 2 equiv. of [C4H(CH2NMe2)-2] in heptane via deamination. Reacting compound 1 with 2 equiv. of phenyl isocyanate at room temperature in diethyl ether results in the PhNCO being inserted seletively into hafnium-NEt2 bonds to generate [C4(CH2NMe2)-2]2Hf[PhNC (NEt2)O]2 (2) in 56% yield. Similarly, while reacting 1 with 2 equiv. of phenyl isocyanate for a week in toluene produces a mixture of 2 and [C4(CH2NMe 2)-2]Hf[PhNC(NEt2)O]3 (3). For comparison, reacting Hf(NEt2)4 with 4 equiv. of PhNCO in a toluene solution at room temperature results in the PhNCO inserted into Hf-N bonds, and forms a tetrakis-ureato hafnium compound Hf[PhNC(NEt2)O]4 (4) in 88% yield. A theoretical calculation found that the unpaired electrons of the ureato fragments of 2 are resonance delocalized between the C-O, C-NPh, and C-NEt2 bonds, which are all partially doubly bonded. © 2004 Elsevier B.V. All rights reserved.
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