461695-86-3Relevant academic research and scientific papers
Synthesis and characterization of coordinatively unsaturated alkynyl- and aryl-cobalt complexes with 15 valence electrons, TpiPr2Co-R, bearing the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (TpiPr2)
Yoshimitsu, Shin-Ichi,Hikichi, Shiro,Akita, Munetaka
, p. 3762 - 3773 (2002)
Coordinatively unsaturated 15e alkynyl- (TpiPr2Co-C≡C-R) and aryl-cobalt complexes (TpiPr2Co-aryl) bearing the hydrotris(3,5-diisopropylpyrazolyl)borato ligand (TpiPr2) are prepared by dehydrative condensation of the hydroxo complex [TpiPr2Co(μ-OH)2]2 with 1-alkyne and arylation of the chloro complex TpiPr2Co-Cl with Grignard reagents, respectively. Spectroscopic and crystallographic analyses reveal the apparent C3-symmetrical tetrahedral structures with high-spin electronic configuration (S = 3/2), which should result from the property of the TpiPr2 ligand as a tetrahedral enforcer. The TpiPr2Co and hydrocarbyl fragments, are connected dominantly through σ-bonding interaction, and π-interaction including back-donation is not significant as revealed by EHMO calculations. The Co-C bonds are so polarized as to be readily protonated even by moisture to give the corresponding hydrocarbons, but the reactivity toward unsaturated hydrocarbons turns out to be sluggish. TpiPr2Co-C≡C-COOMe is found to catalyze a rare example of specific linear trimerization of methyl propiolate to give (E,E)-MeOOC(H)C=CH-CH=C(COOMe)-C≡C-COOMe.
