Chemistry of boranes. XXVII. Lewis acidity of some substituted 1,2-dicarba-closo-dodecaboranes

Identification of an intermediate in the deboronation of ortho-carborane: an adduct of ortho-carborane with two nucleophiles on one boron atom

“…11 As we previously reported the significance of the interactions between the most electron-poor 3(6)-boron atom of ortho-carboranes and solvents involved in solvolysis occurring adjacent to the carborane moiety, 12 so we examined systematically the reactions of ortho-carboranes with several pyridines. The reaction of 1-bromo-ortho-carborane ( 4) with pyridine at room temperature for 20 h afforded the 1 : 2 adduct (6a; C 12 H 21 B 10 N 2 Br from elemental analysis) in 99% yield (Table 1, run 1); this was expected to be the same product as that isolated by Ples˘ek et al 11 However, X-ray crystallography showed that the structure of 6a was different from their proposed structure, as shown in Fig. 2b and Fig.…”

Rapid Cage Degradation of 1-Formyl- and 1-Alkyloxycarbonyl-Substituted 1,2-Dicarba-closo-dodecaboranes by Water or Methanol in Polar Organic Solvents

“…The reaction of several C-and B-brominated 1,2-dicarba-closo-dodecaboranes with a variety of Lewis bases has also been described. 4 Room-temperature cage opening of 1-methyl-2-cyano-o-carborane 5 and 1,2-dichloro-ocarborane 6 in methanol has also been reported. The mechanism of degradation is thought to involve an initial nucleophilic attack upon the 3 or 6 boron atom, which are the most electropositive boron atoms in the icosahedron.…”

“…The conversion of unsubstituted and alkyl substituted closo ortho -carboranes and meta -carboranes to their respective dicarbaundecaborane (nido) analogues by alkoxide and amine bases has been widely studied. The reaction of several C- and B-brominated 1,2-dicarba- closo -dodecaboranes with a variety of Lewis bases has also been described . Room-temperature cage opening of 1-methyl-2-cyano- o -carborane and 1,2-dichloro- o -carborane in methanol has also been reported.…”

Synthesis and Reactivity of 4,5‐[1,2‐Dicarba‐closo‐dodecaborano(12)]‐1,3‐diselenacyclopentane: Opening of the Icosahedron to Give a Zwitterionic Intermediate and Conversion into 7,8‐Dicarba‐nido‐undecaborate(1−)

“…Clearly, compounds 6 a,b correspond to intermediates prior to base-assisted degradation or deboronation of the icosahedral ortho-carborane. Such an intermediate has already been proposed two times, either with an incorrect structure [24] or without convincing proof. [25] However, recently this type of intermediate was isolated for ortho-carboranes that contain one or two C À Br bonds, as in the case of 10, derived from the unknown 10-B(H)py 2 -nido-7,8-C 2 B 10 H 11, 11.…”