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 o rthometalated complex [Pd{C6H4(CH2NHCH2Ph)-2}(mu-OAc)](2) (1) is obtained. Metathetical reaction of 1 with NaBr affords the corresponding bromo-bridgi ng dimer [Pd(C6H4(CH2NHCH2Ph)-2}(mu-Br)](2) (2). Neutral ligands split the bromo bridge to give monomeric complexes [Pd{C6H4(CH2-NHCH2Ph)-2)Br(L)] [L = PPh3, (3a), NH(CH2Ph)(2) (3b)]. Complexes [Pd(C6H4(CH2NHCH2Ph)-2)(acac)] (4) or [Pd{C6H4(CH2NHCH2Ph)-2)L-2]ClO4 [L = py (5a), L-2 = 1,5-cyclooctadie ne (5b)] can be obtained by reacting complex 2 with [Tl(acac)] or with AgCl O4 and the free ligand. Complex 2 reacts with RC drop CR (R = Me, Et, Ph) t o give [Pd{C(R)=C(R)C(R)=C(R)-C6H4(CH2NHCH2Ph)-2}Br] ER = Me (6a), Et (6b), Ph (6c)] through a double insertion of the alkyne into the Pd-C bond. Comp lex 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)]. Co mplexes 6 insert CO or isocyanides R'NC into the C-Pd bond to give 10-membe red 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' = Bu-t, R = Me (10a), Et (10b); R' = C6H3-Me-2-2,6, R = Me (11a), Et (11b)]. Complex ga 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), (BuNC)-Bu-t (13), phen (14)]. The crystal struc tures of 2 . CH2Cl2, 7, 9a, and 13 have been solved.