Synthesis, structure, and reactivity of C-isopropyl-ortho-carborane organoboron derivatives

Abstract

A reaction of isopropyl-ortho-carborane with n-butyllithium, followed by treatment of the lithium derivative formed with boron trichloride, chlorodimethoxyborane, or chloropinacolatoborane furnished C-boryl-ortho-carboranes 1a-c. Further functionalization of 1-Cl₂B-2-Prⁱ-1,2-C₂B₁₀H₁₀ (1a) with pentafluorophenylmagnesium bromide or pentafluorophenol led to 1-(C₆F₅)₂B-2-Prⁱ-1,2-C₂B₁₀H₁₀ (2) and (1-(C₆F₅O)B-2-Prⁱ-1,2-C₂B₁₀H₁₀)₂O (3), respectively. A reaction of 1-(MeO)₂B-2-Prⁱ-1,2-C₂B₁₀H₁₀ (1b) with the complexes of BH₃ with THF and dimethyl sulfide gave rise to carboranylborane adducts 4a,b. The use of the complex of 1-H₂B-2-Prⁱ-1,2-C₂B₁₀H₁₀ with dimethyl sulfide 4b as a hydroboration agent in the reactions with hex-1-ene and phenylacetylene allowed us to obtain dialkyl- and di(phenylolefin)-containing C-isopropyl-ortho-carboranylboranes, respectively. The reaction of C-isopropyl-ortho-carboranyldimethoxyborane with triallylborane led to the substitution of only one of two MeO groups with the allyl one, which is explained by the steric effects of bulky carboranyl substituent in the precursor. Compounds obtained are characterized by X-ray diffraction analysis.