Synthesis and Reactivity of Four-Membered Azapalladacycles Derived from N,N-Dialkyl-2-iodoanilines:  Insertion Reactions of Carbenes into the Carbon−Palladium Bond

Three new four-membered azapalladacycles derived from N, N -dialkyl-2-iodoanilines have been synthesized: [Pd( κ 2 -C 6 H 4 NMe 2 -2)I(PPh 3 )] ( 4a ), [Pd{ κ 2 -C 6 H 4 N(Me)CH 2 Ph-2}I(PPh 3 )] ( 4b ), and [Pd{ κ 2 -C 6 H 4 N(Me)Pr-2}I(PPh 3 )] ( 4c ). On heating in solution azapalladacycles 4a and 4c undergo aryl−aryl interchange between the palladium atom and the phosphine ligand to give the phosphanyl-amine palladium complexes [PdPhI(PNMe 2 )] ( 7a ) and [PdPhI{PN(Me)Pr}] ( 7c ), respectively. Azapalladacycles 4a − c react with dichlorocarbene to give acyl palladium complexes [Pd{ κ 2 -C(O)C 6 H 4 NMe 2 -2}I(PPh 3 )] ( 8a ), [Pd{ κ 2 -C(O)C 6 H 4 N(Me)CH 2 Ph-2}I(PPh 3 )] ( 8b ), and [Pd{ κ 2 -C(O)C 6 H 4 N(Me)Pr-2}I(PPh 3 )] ( 8c ), respectively. Smooth insertion of N 2 CHCO 2 Et into the carbon−palladium bond of azapalladacycles 4a − c results in the formation of the single-insertion products [Pd{ κ 2 -CH(CO 2 Et)C 6 H 4 NMe 2 -2}I(PPh 3 )] ( 9a ), [Pd{ κ 2 -CH(CO 2 Et)C 6 H 4 N(Me)CH 2 Ph-2}I(PPh 3 )] ( 9b ), and [Pd{ κ 2 -CH(CO 2 Et)C 6 H 4 N(Me)Pr-2}I(PPh 3 )] ( 9c ), respectively. On the other hand, complexes 4a and 4c react with N 2 CHTMS to give mainly the single-insertion products [Pd{ κ 2 -CH(SiMe 3 )C 6 H 4 NMe 2 -2}I(PPh 3 )] ( 10a ) and [Pd{ κ 2 -CH(SiMe 3 )C 6 H 4 N(Me)Pr-2}I(PPh 3 )] ( 10c ), respectively, while under similar reaction conditions 4b affords N -benzyl- N -methyl-2-[( Z )-2-(trimethylsilyl)vinyl]aniline ( 11b ) as a consequence of a double-insertion process. Solid state structures of palladium complexes 4b, 8b ·EtOAc, 9a, 9b, and 9c ·Et 2 O have been determined by X-ray analysis.