Addition of a phosphinidene complex to C=N bonds: P-ylides, azaphosphiridines, and 1,3-dipolar cycloadditions

dThe terminal phosphinidene complex PhPW(CO)(5) adds to the imine bond of P hHC=N-Ph to give 3-membered ring azaphosphiridines, which undergo ring-expa nsion with an additional imine to yield a set of four isomeric five-membere d ring diazaphospholanes. Treatment with the diimines PhHC=N(CH2)(n)-N=CHPh (n = 2,3,4) results instead-in all three cases-in only a single isomer of the (CH2)(n), bridged diazaphospholane. For n = 2 or 3, this aminal group i s easily hydrolyzed to afford new 6- and 7-membered ring heterocycles. No i ntermediate azaphosphiridine complex is observed during the addition reacti on to the diimines. B3LYP/6-31G* calculations on an unsubstituted, uncomple xed system suggest-ylide of st that the initially formed P,N-yield of the H 2C=N-(CH)(2)-N=CH2 diimine both kinetically and thermodynamically favors an intramolecular 1,3-dipolar cycloaddition over an imine insertion into the CPN ring of an intermediate azaphosphiridine. Single-crystal X-ray structur es for the (CH2)(2)-bridged azaphospholane complex and the HCl adduct of th e 7-membered hydrolysis product are presented.