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.