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(κ2-C6H4NMe2-2)I(PPh3)] (4a), [Pd{κ2-C6H4N(Me)CH2Ph-2}I(PPh3)] (4b), and [Pd{κ2-C6H4N(Me)Pr-2}I(PPh3)] (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(PNMe2)] (7a) and [PdPhI{PN(Me)Pr}] (7c), respectively. Azapalladacycles 4ac react with dichlorocarbene to give acyl palladium complexes [Pd{κ2-C(O)C6H4NMe2-2}I(PPh3)] (8a), [Pd{κ2-C(O)C6H4N(Me)CH2Ph-2}I(PPh3)] (8b), and [Pd{κ2-C(O)C6H4N(Me)Pr-2}I(PPh3)] (8c), respectively. Smooth insertion of N2CHCO2Et into the carbon−palladium bond of azapalladacycles 4ac results in the formation of the single-insertion products [Pd{κ2-CH(CO2Et)C6H4NMe2-2}I(PPh3)] (9a), [Pd{κ2-CH(CO2Et)C6H4N(Me)CH2Ph-2}I(PPh3)] (9b), and [Pd{κ2-CH(CO2Et)C6H4N(Me)Pr-2}I(PPh3)] (9c), respectively. On the other hand, complexes 4a and 4c react with N2CHTMS to give mainly the single-insertion products [Pd{κ2-CH(SiMe3)C6H4NMe2-2}I(PPh3)] (10a) and [Pd{κ2-CH(SiMe3)C6H4N(Me)Pr-2}I(PPh3)] (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·Et2O have been determined by X-ray analysis.