Donor-stabilisierte Trisalkinylborane. Kristallstruktur von H5C5N–B(C≡CH)3 und Elektronenstruktur von B(C≡CH)3 / Donor-Stabilized Trisalkinylboranes. Crystal Structure of H5C5N–B (C≡CH)3 and Electronic Structure of B(C≡CH)3

The synthesis and properties of donor-stabilized trisethinylborane compounds 1 - 3 (donor = pyridine, tetrahydrothiophene, tetrahydrofuran) and of the tris(trimethylsilylethinyl)boranediethylether adduct 4 are reported. Attempts to obtain donor-free trisorganylethinylboranes have failed. 11B NMR data of 1 - 4 and the X-ray structure analysis of 1 and 3 reveal that the boron atoms are four-coordinated. The B-C bonds in 1 are somewhat longer and the C≡C bonds shorter than in diborylacetylenes.