Cyclopalladated complexes derived from benzamidoxime†
Abstract
Cyclopalladated benzamidoxime complexes [Pd{C,N-C6H4{C(NH2)NOH}-2}Cl(L)] (L = PTol3, Tol = C6H4Me-4 (2a); XyNC, Xy = C6H3Me2-2,6 (2b); pic, C5H4Me-4 (2c)), [Pd{C,N-C6H4{C(NH2)NOH}-2}(L2)]ClO4 (L = pic (3a); L2 = 4,4′-di-tert-butyl-2,2′-bipyridine, tbbpy (3b)) and PPN[Pd{C,N-C6H4{C(NH2)NOH}-2}Cl2] (4) are prepared by reacting [Pd{C,N-C6H4{C(NH2)NOH}-2}(μ-Cl)]2 (1) with the appropriate neutral ligand or with [PPN]Cl, respectively. The cationic complexes are obtained in the presence of NaClO4. The reaction of 2a with KtBuO affords the dinuclear oximato complex [Pd{μ-C,N,O-C6H4{C(NH2)NO}-2}(PTol3)]2 (5) or, in the presence of ClCH2py·HCl, the pincer derivative [Pd{C,N,N′-C6H4{C(NH2)NOCH2(C5H4N-2)}-2}(PTol3)]ClO4 (6). Complex 2b reacts with XyNC to give the iminobenzoyl complex [Pd{C,N-C(NXy)C6H4{C(NH2)NOH}-2}Cl(CNXy)] (7) resulting from the insertion of XyNC into the Pd–C bond. The dinuclear complex [{Pd(tbbpy)}2{C,N,N′,O-C6H4{C(NH)NO}-2}]ClO4 (8) bearing a bridging tetradentate benzimido(oximate) ligand is obtained by reacting Pd(OAc)2 with tbbpy and the metal–ligand complex 3b. The crystal structures of complexes 2a, 6, 7 and 8 have been determined.