Synthesis and Characterization of Coordinatively Unsaturated Alkynyl- and Aryl-Cobalt Complexes with 15 Valence Electrons, TpiPr2Co-R, Bearing the Hydrotris(3,5-diisopropy
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- 作者：Shin-ichi Yoshimitsu ; Shiro Hikichi ; and Munetaka Akita
- 刊名：Organometallics
- 出版年：2002
- 出版时间：September 2, 2002
- 年：2002
- 卷：21
- 期：18
- 页码：3762 - 3773
- 全文大小：292K
- 年卷期：v.21,no.18(September 2, 2002)
- ISSN：1520-6041
文摘
Coordinatively unsaturated 15e alkynyl- (TpiPr2Co-C
C-R) and aryl-cobalt complexes(TpiPr2Co-aryl) bearing the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (TpiPr2) areprepared by dehydrative condensation of the hydroxo complex [TpiPr2Co(
-OH)2]2 with1-alkyne and arylation of the chloro complex TpiPr2Co-Cl with Grignard reagents, respectively. Spectroscopic and crystallographic analyses reveal the apparent C3-symmetricaltetrahedral structures with high-spin electronic configuration (S = 3/2), which should resultfrom the property of the TpiPr2 ligand as a tetrahedral enforcer. The TpiPr2Co and hydrocarbylfragments are connected dominantly through 
-bonding interaction, and 
-interactionincluding back-donation is not significant as revealed by EHMO calculations. The Co-Cbonds are so polarized as to be readily protonated even by moisture to give the correspondinghydrocarbons, but the reactivity toward unsaturated hydrocarbons turns out to be sluggish.TpiPr2Co-CC-COOMe is found to catalyze a rare example of specific linear trimerizationof methyl propiolate to give (E,E)-MeOOC(H)C=CH-CH=C(COOMe)-CC-COOMe.
C-R) and aryl-cobalt complexes(TpiPr2Co-aryl) bearing the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (TpiPr2) areprepared by dehydrative condensation of the hydroxo complex [TpiPr2Co(-OH)2]2 with1-alkyne and arylation of the chloro complex TpiPr2Co-Cl with Grignard reagents, respectively. Spectroscopic and crystallographic analyses reveal the apparent C3-symmetricaltetrahedral structures with high-spin electronic configuration (S = 3/2), which should resultfrom the property of the TpiPr2 ligand as a tetrahedral enforcer. The TpiPr2Co and hydrocarbylfragments are connected dominantly through -bonding interaction, and -interactionincluding back-donation is not significant as revealed by EHMO calculations. The Co-Cbonds are so polarized as to be readily protonated even by moisture to give the correspondinghydrocarbons, but the reactivity toward unsaturated hydrocarbons turns out to be sluggish.TpiPr2Co-CC-COOMe is found to catalyze a rare example of specific linear trimerizationof methyl propiolate to give (E,E)-MeOOC(H)C=CH-CH=C(COOMe)-CC-COOMe.