CYCLOPALLADATED COMPLEXES OF 2-ACETYLPYRIDINE PHENYLHYDRAZONE - A TERDENTATE C,N,N' DONOR LIGAND

Cyclopalladated complexes of 2-acetylpyridine phenylhydrazone [Pd(C6H4N(H)N=C(CH3)-C5H4N)Cl] (2) and [Pd(C6H4N(H)N=C(CH3)C5H4N)L]BF4 (L = PPh3 (3a), P(OMe)3 (3b), P(OPh)3 (3c), CH3C5H4N (3d), C4H8S (3e)) containing readily deprotonable N-H bonds have been prepared. Blue zwitterionic species, obtained after deprotonation of the cationic complexes, are characterized by their reactivity as nucleophiles toward H+ or CH3I; eg. deprotonated (3a) reacts with CH3I to give [Pd(C6H4N(CH3)N=C(CH3)C5H4N)I] (5). Some aspects of the orthometalation reaction mechanism of phenylhydrazones are discussed. The crystal and molecular structure of the face to face complex {[Pd(C6H4N(H)N=C(CH3)C5H4N)]2(mu-Ph2-PCH2PPh2)}[BF4]2.OEt2.NCMe (4) [monoclinic, space group P2(1)/n, a = 15.911(4) angstrom, b = 18.902(6) angstrom, c = 18.563(4) angstrom, beta = 95.43(2)-degrees, Z = 4, R = 0.032, and R(w) = 0.034 for 7038 observed reflections] shows a nonbonding Pd-Pd distance of 3.114(1) angstrom.