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Synthesis and Reactivity of Four-Membered Azapalladacycles Derived from N,N-Dialkyl-2-iodoanilines: Insertion Reactions of Carbenes into the Carbon−Palladium Bond
journal contribution
posted on 2004-03-15, 00:00 authored by Daniel Solé, Lluís Vallverdú, Xavier Solans, Mercè Font-Bardia, Josep BonjochThree 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 4a−c 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 4a−c 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.