Abstract
The RSCH2CH2B(C6F5)2 boranes 3a (R=Ph) and 3b (R=Et) were in situ generated by HB(C6F5)2 hydroboration of the respective vinylthioethers. Their treatment with R1-C≡C- SiMe3 acetylenes resulted in clean 1,1-carboboration to give the respective RSCH2CH2-substituted alkenylboranes 4 (3 examples). Likewise, the reagents 3 underwent 1,1-carboboration with the acetylenes Ar2P-C≡C-SiMe3 to give the tetrasubstituted alkenylboranes 6, featuring a geminal pair of RSCH2CH2=B(C6F5)2 substituents at one carbon atom and the Me3Si=PAr2 pair at the other (3 examples). The compounds 6 feature an internal B···P interaction. The conceptually related Mes2PCH2CH2B(C6F5)2 borane (2) does not undergo 1,1-carboboration with ArS-C≡C-SiMe3 but forms the 1,2-P=B-FLP addition product 7 to the acetylene instead. Compounds 4a, 4c, 6a, and 7 were characterized by X-ray diffraction.
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