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Do Rhodium Bis(σ‐amine‐borane) Complexes Play a Role as Intermediates in Dehydrocoupling Reactions of Amine‐boranes?
Author(s) -
Butera Valeria,
Russo Nino,
Sicilia Emilia
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.201102365
Subject(s) - boranes , borane , rhodium , chemistry , amine gas treating , intramolecular force , dimer , hydrogen bond , medicinal chemistry , molecule , photochemistry , combinatorial chemistry , organic chemistry , catalysis , boron
Abstract The recently synthesized rhodium complex [Rh{P(C 5 H 9 ) 2 (η 2 ‐C 5 H 7 )}(Me 2 HNBH 3 ) 2 ]BAr F 4 ( 2 ), which incorporates two amine‐boranes coordinated to the rhodium center with two different binding modes, namely η 1 and η 2 , has been used to probe whether bis(σ‐amine‐borane) motifs are important in determining the general course of amine‐boranes dehydrocoupling reactions. DFT calculations have been carried out to explore mechanistic alternatives that ultimately lead to the formation of the amine‐borane cyclic dimer [BH 2 NMe 2 ] 2 ( A ) by hydrogen elimination. Sequential concerted, on‐ or off‐metal, intramolecular dehydrogenations provide two coordinated amine‐borane molecules. Subsequent dimerization is likely to occur off the metal in solution. In spite of the computationally confirmed presence of a BH⋅⋅⋅NH hydrogen bond between amine‐borane ligands, neither a simple intermolecular route for dehydrocoupling of complex 2 is operating, nor seems [Rh{P(C 5 H 9 ) 2 (η 2 ‐C 5 H 7 )} B ] + to be important for the whole dehydrocoupling process.