Cyclopalladated azido complexes containing C,N-donor (HC similar to N=2-(2 '-thienyl)pyridine, azobenzene, 3,3 '-dimethyl azobenzene, N,N '-dimethylbenzylamine, 2-phenylpyridine) ligands: reactivity towards organic unsaturated compounds and catalytic properties

Abstract

Cyclopalladated azido dimers having various C,N-donor ligands, [Pd(mu-N-3)(C,N-L-n)](2) ((LH)-H-1 = 2-(2 '-thienyl)pyridine; (LH)-H-2 = azobenzene; (LH)-H-3 = 3,3 '-dimethylazobenzene; (LH)-H-4 = N,N '-dimethyl-benzylamine; (LH)-H-5 = 2-phenylpyridine), underwent cleavage with tertiary (or chelating) phosphines to form the cyclopalladated [Pd(N-3)(PR3)(C,N-L)], the sigma-bonded [Pd(N-3)(PR3)(2)(C-L)], or the dinuclear-cyclopalladated [PdN3(PR3)(C,N-L)](2)(mu-P similar to P) complexes. In particular, treating [Pd(mu-N-3)(C,N-L)](2) with the basic chelating phosphine (depe or dmpe) produced the homoleptic bis(chelating) complex [Pd(C,N-L-n)(2)] (n = 1-3). Complex [Pd(N-3)(PR3)(C,N-L-4)] or [Pd(N-3)(PR3)(2)(C-L-4)] reacted with aryl isocyanides to selectively give the imidoyl [Pd(N-3)(-C=N-Ar)(PR3)(N-L-4)] or the imidoyl carbodiimido complex [Pd(N=C=N-Ar)(-C=N-Ar)(PR3)(N-L-4)], which was formed by the CN-Ar insertion into the orthometallated Pd-C bond on the phenyl moiety or the interaction into the Pd-N-3 bond of the supporting ligand. In addition, reactions of [Pd(N-3)(PR3)(2)(C-L-n)] (n = 1, 2, 4) with R-NCS {R = i-Pr, C6H4-NCS, (CH3)(3)Si} gave the S-coordinated tetrazole-thiolato Pd(II) complexes. Finally, the catalytic activity of the cyclopalladated azido complexes was evaluated.