Hydroboration of Phosphaalkynes by HB(C6 F5 )2.

The hydroboration of phosphaalkynes with Piers' borane (HB(C6 F5 )2 ) generated unusual phosphaalkenylboranes [RCH=PB(C6 F5 )2 ]2 that persisted as dimers in both solution and the solid state. These P2 B2 heterocycles underwent ring opening when subjected to nucleophiles, such as pyridine and tert-butylisocyanide, to yield monomeric phosphaalkenylborane adducts RCH=PB(C6 F5 )2 (L). DFT calculations were performed to probe the nature of the interaction of phosphaalkynes with boranes.