Photochemically generated nitrilium phosphane-ylid tungsten complexes and their reactivity towards alkyne and nitrile derivatives

The photochemically generated nitrilium phosphane-ylid tungsten complex 2 r eacts with different activated alkynes, dimethyl acetylenedicarboxylate (DM AD) (i) and ethyl acetylenecarboxylate (ii), and nitriles, ethyl cyanoforma te (ECF) (iii) and 1-piperidinonitrile (iv), giving [3+2] cycloaddition pro ducts such as the 2H-1,2-azaphosphole complexes 3 (i) and 4 (ii), the 2H-1, 4,2-diazaphosphole complex 5 (iii) and the 2H-1,3,2-diazaphosphole complex 7 in good to excellent yields, the latter complexes, 4-7, being formed regi oselectively; the structure of the first ester-functionalized 2H-1,4,2-diaz aphosphole complex 5 was established by X-ray analysis.