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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−)
Author(s) -
Wrackmeyer Bernd,
Klimkina Elena V.,
Milius Wolfgang,
Bauer Tobias,
Kempe Rhett
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002277
Subject(s) - carborane , chemistry , crystallography , pyridine , nuclear magnetic resonance spectroscopy , dichloromethane , boron , salt (chemistry) , reactivity (psychology) , stereochemistry , medicinal chemistry , solvent , organic chemistry , medicine , alternative medicine , pathology
Abstract The reaction of the 1,2‐diselenolato‐1,2‐dicarba‐ closo ‐dodecaborane(12) dianion [1,2‐(1,2‐C 2 B 10 H 10 )Se 2 ] 2− with dichloromethane (CH 2 Cl 2 or CD 2 Cl 2 ) in the presence of donor solvents gave 4,5‐[1,2‐dicarba‐ closo ‐dodecaborano(12)]‐1,3‐diselenacyclopentane, the title compound, which was characterized by X‐ray structural analysis and NMR spectroscopy ( 1 H, 11 B, 13 C, and 77 Se). In the presence of pyridine, opening of the icosahedron took place, and a zwitterionic intermediate was isolated and fully characterized in the solid state by X‐ray diffraction and in solution by multinuclear magnetic resonance techniques. Although such types of intermediates, prior to deboronation of the ortho ‐carborane cage, have been proposed several times, this is first example for which the structure has been confirmed unambiguously. This intermediate possesses a nido structure and contains a 7,8‐dicarba‐ nido ‐undecaborate(1−) anion and a boronium cation, the latter with two pyridine rings linked to the boron atom, which has been extruded from the cage. It was shown that this process is reversible as long as the deboronation is not complete. The formation of the intermediate is accompanied by deboronation, which leads to the 7,8‐dicarba‐ nido ‐undecaborate(1−) anion. The latter was prepared independently by conventional routes from the title compound, isolated as crystalline material as the tetrabutyl ammonium salt, and characterized by X‐ray structural analysis and multinuclear magnetic resonance spectroscopy ( 1 H, 11 B, 13 C, and 77 Se).