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Chlorination of the terminal hydrogen atoms in the hydrogen-rich group 5 dimetallaboranes (Cp*M)2(B2H6)2 (M = Nb, Ta)
Rini Prakash, Kirubakaran Bakthavachalam, Babu Varghese,
Published in Elsevier B.V.
2017
Volume: 846
   
Pages: 372 - 378
Abstract
Reaction of Cp*NbCl4 with 4 equivalents of LiBH4.thf followed by thermolysis with BH3.thf in xylene yielded a chlorine substituted [(Cp*Nb)2(B2H5Cl)2], 1 and its parent [(Cp*Nb)2(B2H6)2], 2. Under the same reaction conditions, Cp*TaCl4 afforded the Ta analogue of 1, [(Cp*Ta)2(B2H5Cl)2], 4 and a monochlorinated metallaborane [(Cp*TaCl)2B5H10Cl], 5. Reaction of 2 with CH2Cl2 for a prolonged period resulted in the formation of a terminal perchlorinated niobaborane [(Cp*Nb)2(B2H4Cl2)2], 3 along with 1. Formation of 1 and 3 have also been achieved at a faster rate using other chlorinated solvents such as CHCl3 and CCl4. In contrast, reaction of [(Cp*Ta)2(B2H6)2] with CH2Cl2 for a long time yielded the known [(Cp*TaCl)2B5H11] and its monochlorinated derivative 5. All the compounds have been characterized by mass spectrometry, 1H, 11B{1H}, 13C{1H} NMR spectroscopy and the structural types were unequivocally established by crystallographic analysis of the compounds 1 and 3–5. Density functional theory (DFT) calculations reveal geometries in agreement with the structural determinations. Increase in the HOMO−LUMO energy gap due to chlorination of the parent metallaboranes verifies the substitution, which in turn shows good agreement with the electronic spectra of the molecules 1–3. © 2017 Elsevier B.V.
About the journal
JournalData powered by TypesetJournal of Organometallic Chemistry
PublisherData powered by TypesetElsevier B.V.
ISSN0022328X
Open AccessNo
Concepts (15)
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    Atoms
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    Chlorination
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    Mass spectrometry
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    Niobium
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    Nuclear magnetic resonance spectroscopy
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    Tantalum
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    CHLORINATED SOLVENT
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    CRYSTALLOGRAPHIC ANALYSIS
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    Electronic spectrum
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    ELECTROPHILIC SUBSTITUTIONS
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    PERCHLORINATION
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    Reaction conditions
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    STRUCTURAL DETERMINATION
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    STRUCTURAL TYPE
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    Density functional theory