Palladium-Assisted Formation of Carbon−Carbon Bonds. 8.¹ 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{C 6 H 4 (CH 2 NHCH 2 Ph)-2}(μ-OAc)] 2 ( 1 ) is obtained. Metathetical reaction of 1 with NaBr affords the corresponding bromo-bridging dimer [Pd{C 6 H 4 (CH 2 NHCH 2 Ph)-2}(μ-Br)] 2 ( 2 ). Neutral ligands split the bromo bridge to give monomeric complexes [Pd{C 6 H 4 (CH 2 NHCH 2 Ph)-2}Br(L)] [L = PPh 3, ( 3a ), NH(CH 2 Ph) 2 ( 3b )]. Complexes [Pd{C 6 H 4 (CH 2 NHCH 2 Ph)-2}(acac)] ( 4 ) or [Pd{C 6 H 4 (CH 2 NHCH 2 Ph)-2}L 2 ]ClO 4 [L = py ( 5a ), L 2 = 1,5-cyclooctadiene ( 5b )] can be obtained by reacting complex 2 with [Tl(acac)] or with AgClO 4 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)C 6 H 4 (CH 2 NHCH 2 Ph)-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 = CF 3 SO 3 ) and neutral ligands to give [Pd{C(R) C(R)C(R) C(R)C 6 H 4 (CH 2 NHCH 2 Ph)-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)C 6 H 4 (CH 2 NHCH 2 Ph)-2}Br] [E = O, R = Me ( 9a ), Et ( 9b ), Ph ( 9c ); E = NR‘, R‘ = t Bu, R = Me ( 10a ), Et ( 10b ); R‘ = C 6 H 3 Me 2 -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)C 6 H 4 (CH 2 NHCH 2 Ph)-2}L]OTf [R = Me, L = py ( 12 ), t BuNC ( 13 ), phen ( 14 )]. The crystal structures of 2 ·CH 2 Cl 2, 7, 9a, and 13 have been solved.