Formation of macrocyclic ring systems by carbonylation of trifunctional P/B/B frustrated Lewis pairs.

The trifunctional P/B/B frustrated Lewis pairs featuring bulky aryl groups at phosphorus [Dmesp (), Tipp (), Mes* ()] react with H by heterolytic hydrogen splitting followed by cleavage of HB(CF) to give the zwitterionic six-membered heterocyclic PH phosphonium/borate products . Compounds react with carbon monoxide by means of a Lewis acid induced CO insertion/rearrangement sequence that eventually results in the formation of the macrocyclic dimers . The respective carbonylation reaction of the Mes*P/B/B FLP gives the macrocyclic trimer . The new products were characterized spectroscopically and by X-ray diffraction and the reaction mechanism was analyzed by DFT calculations.