Titanacarborane mediated C-N bond forming/breaking reactions

Constrained-geometry titanacarboranes [sigma: eta(1):eta(5)-(OCH2)(R2NCH2)C2B9H9]Ti(NR2) (R = Me, Et) are synthesized via an unexpected reaction of [Me3NH][mu-7,8-CH2OCH2-7,8-C2B9H10] with Ti(NR2)(4) (R = Me, Et), involving a C-O bond cleavage and C-N bond formation. These complexes can be readily converted to new amide species or alkoxide by reacting with amines or esters, respectively. Insertion of a series of unsaturated molecules into the Ti-N bond of the aforementioned complexes results in the formation of various half-sandwich titanacarboranes. [sigma: eta(1): eta(5)-(OCH2)(Me2NCH2)C2B9H9]Ti(NMe2) is also able to efficiently catalyze the hydroamination of carbodiimides and the transamination of guanidines. These results are summarized in this brief account. (C) 2008 Elsevier B.V. All rights reserved.