Diazo compounds and palladium-aryl complexes: trapping the elusive carbene migratory insertion organometallic products

The reactions of Pd-aryl complexes with diazo compounds N 2 CH-CH&z.dbd;CHPh and N 2 CHPh allowed us to isolate the organometallic products formed right after the migratory insertion of a non-stabilized CHR carbene into the Pd-aryl bond. η 3 -Allylic and η 3 -benzylic palladium complexes were formed respectively. This is compelling experimental evidence for the key step in the palladium-catalyzed cascade transformations of diazo derivatives leading to multiple C-C or C-X bond formation. Caught right after migratory insertion of a non-stabilized carbene into a Pd-Ar bond. The new allylic and benzylic palladium complexes model key intermediates in Pd-catalyzed coupling reactions of diazoalkanes.