η2-Coordination of a phosphaalkyne to an amino olefin nickel complex and regioselective catalyzed cyclooligomerization to dewar 1,3,5-triphosphabenzene

Article abstract of DOI:10.1002/ejic.201301135

We report herein an efficient synthesis of a Dewar-triphosphabenzene derived from [2+2+2] cycloaddition of three phosphaalkyne molecules promoted by an amino olefin Ni⁰ complex as the catalyst. Amino diolefin Ni ^I complex 1 serves as a precursor complex that reacts with triphenylmethylphosphaethyne under reducing conditions at low temperature to give Ni⁰ complex 3 with a coordinated phosphaalkyne in a η²-mode. The structure of 3 was determined by X-ray diffraction methods and suggests a bonding situation for the phosphaalkyne that is between a side-on coordinated C≡P molecule and a metallaphosphacyclopropene structure. The reaction of 3 with a 10-fold excess of phosphaethylene under reducing conditions at room temperature resulted in the formation of 2,4,6-tris(triphenylmethyl)-Dewar-1,3,5-triphosphabenzene (4) in good yield. Copyright