A Unique Frustrated Lewis Pair Pathway to Remarkably Stable Borata-Alkene Systems

The hydroboration of a conjugated diphenylphosphanylenyne with Piers' borane [HB(C6F5)2] gives three products. The major product is probably formed by generation of a geminal P/B frustrated Lewis pair that undergoes rapid and subsequent intramolecular conjugate addition of the phosphane to the dienyl borane unit to yield a unique phosphonium borata-diene. The minor products originate from alternative regioisomeric hydroboration reactions. Two examples of the new phosphonium borata-olefin products were characterized by X-ray diffraction.