title: Do rhodium bis(σ-amine-borane) complexes play a role as intermediates in dehydrocoupling reactions of amine-boranes?
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.
authors: Department of Chemistry, Università della Calabria, 87036 Arcavacata di Rende.
authors: Valeria
authors: V
authors: Butera
authors: Nino
authors: N
authors: Russo
authors: Emilia
authors: E
authors: Sicilia