Palladium-Assisted Formation of Carbon−Carbon Bonds. 8. Synthesis and Reactivity toward Internal Alkynes, Carbon Monoxide, and Isocyanides of Orthopalladated Dibenzylamine Complexes

By refluxing of dibenzylamine and [Pd(OAc)2]3 (3.2:1) in acetone, the orthometalated complex [Pd{C6H4(CH2NHCH2Ph)-2}(μ-OAc)]2 (1) is obtained. Metathetical reaction of 1 with NaBr affords the corresponding bromo-bridging dimer [Pd{C6H4(CH2NHCH2Ph)-2}(μ-Br)]2 (2). Neutral ligands split the bromo bridge to give monomeric complexes [Pd{C6H4(CH2NHCH2Ph)-2}Br(L)] [L = PPh3, (3a), NH(CH2Ph)2 (3b)]. Complexes [Pd{C6H4(CH2NHCH2Ph)-2}(acac)] (4) or [Pd{C6H4(CH2NHCH2Ph)-2}L2]ClO4 [L = py (5a), L2 = 1,5-cyclooctadiene (5b)] can be obtained by reacting complex 2 with [Tl(acac)] or with AgClO4 and the free ligand. Complex 2 reacts with RC⋮CR (R = Me, Et, Ph) to give [Pd{C(R)C(R)C(R)C(R)C6H4(CH2NHCH2Ph)-2}Br] [R = Me (6a), Et (6b), Ph (6c)] through a double insertion of the alkyne into the Pd−C bond. Complex 6a reacts with Tl(OTf) (OTf = CF3SO3) and neutral ligands to give [Pd{C(R)C(R)C(R)C(R)C6H4(CH2NHCH2Ph)-2}L]OTf [R = Me, L = py (7), phen (8)]. Complexes 6 insert CO or isocyanides R‘NC into the C−Pd bond to give 10-membered palladacycles [Pd{C(R)C(R)C(R)C(R)C(E)C6H4(CH2NHCH2Ph)-2}Br] [E = O, R = Me (9a), Et (9b), Ph (9c); E = NR‘, R‘ = tBu, R = Me (10a), Et (10b); R‘ = C6H3Me2-2,6, R = Me (11a), Et (11b)]. Complex 9a reacts with Tl(OTf) and neutral ligands to give [Pd{C(O)C(R)C(R)C(R)C(R)C6H4(CH2NHCH2Ph)-2}L]OTf [R = Me, L = py (12), tBuNC (13), phen (14)]. The crystal structures of 2·CH2Cl2, 7, 9a, and 13 have been solved.