Synthesis, Structures, and Donor−Acceptor Adducts of Tris(3,3-dimethyl-1-butynyl)borane

The synthesis and properties of tris(3,3-dimethyl-1-butynyl)borane (1), the first donor-free tris(alkynyl)borane, and of its adducts 2 [donor = pyridine (2a), triphenylphosphane (2b), tetrahydrofuran (2c)] are reported. X-ray structure analyses reveal that the B−C bond lengths in 1 are shorter than in 2; however, the C≡C triple bond lengths are similar to those of the donor-stabilized compounds 2a, 2b, and 2c. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)