Cyclopalladated azido complexes containing C,N-donor (HC∼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(μ-N₃)(C,N-Lⁿ)]₂ (L¹H = 2-(2′-thienyl)pyridine; L²H = azobenzene; L³H = 3,3′-dimethylazobenzene; L⁴H = N,N′-dimethylbenzylamine; L⁵H = 2-phenylpyridine), underwent cleavage with tertiary (or chelating) phosphines to form the cyclopalladated [Pd(N₃)(PR₃)(C,N-L)], the σ-bonded [Pd(N₃)(PR₃)₂(C-L)], or the dinuclear-cyclopalladated [PdN₃(PR₃)(C,N-L)]₂(μ-P∼P) complexes. In particular, treating [Pd(μ-N₃)(C,N-L)]₂ with the basic chelating phosphine (depe or dmpe) produced the homoleptic bis(chelating) complex [Pd(C,N-Lⁿ)₂] (n = 1–3). Complex [Pd(N₃)(PR₃)(C,N-L⁴)] or [Pd(N₃)(PR₃)₂(C-L⁴)] reacted with aryl isocyanides to selectively give the imidoyl [Pd(N₃)(–CN–Ar)(PR₃)(N-L⁴)] or the imidoyl carbodiimido complex [Pd(NCN–Ar)(–CN–Ar)(PR₃)(N-L⁴)], which was formed by the CN–Ar insertion into the orthometallated Pd–C bond on the phenyl moiety or the interaction into the Pd–N₃ bond of the supporting ligand. In addition, reactions of [Pd(N₃)(PR₃)₂(C-Lⁿ)] (n = 1, 2, 4) with R–NCS {R = i-Pr, C₆H₄–NCS, (CH₃)₃Si} gave the S-coordinated tetrazole–thiolato Pd(II) complexes. Finally, the catalytic activity of the cyclopalladated azido complexes was evaluated.