Abstract:
Nuclear magnetic resonance spectroscopy has been used
to study donor-acceptor complexes of boron trifluoride with
several ureas, tetramethylthiourea, tetramethylselenourea,
and tetramethylquanidine as well as adducts of tetramethyl-
-urea with BF2Cl, BFC1 2 , and BC1 3 -
A large number of mixed tetrahaloborate ions, including
some of the ternary ones such as BF2CIBr-,have been obtained
by ligand exchange reactions and studied by NMR techniques.
The bonding in these ions is of the same inherent interest
as the bonding in the isoelectronic tetrahalomethanes which
have been the subject of many detailed studies and have been
involved in a controversy concerning the existence of and
the nature of "fluorine hyperconjugation" or C-F P1T- Pn
bonding_
Ligand exchange reactions also gave rise to the difluoroboron
cation, (TMU)20BF2+o The difluoroboron cation has been
observed in solutions of TMU-BF3 , and has been proposed as a
possible intermediate for fluorine exchange reactions in BF3
adducts.
