Palladium complexes of azines, α-diazines and α-2-pyridylazines containing (1R)-(+)-camphor or (1R)-(–)-fenchone groups

Abstract

Mixed monoazines of types H₂CN–NC₁₀H₁₆[C₁₀H₁₆ is a (1R)-(+)-camphor residue (L¹), or a (1R)-(–)-fenchone residue (L²)] or Me₂CN–NC₁₀H₁₆[C₁₀H₁₆ is a (1R)-(+)-camphor residue (L³)], or α-diazines C₁₀H₁₆N–NCH–CHN–NC₁₀H₁₆[C₁₀H₁₆ is a (1R)-(+)-camphor residue (L⁴) or a (1R)-(–)-fenchone residue (L⁵)], or α-2-pyridyl azines C₁₀H₁₆N–NCHC₅H₄N [C₁₀H₁₆ is a (1R)-(+)-camphor residue (L₆) or a (1R)-(–)-fenchone residue (L⁷)] reacted with Na₂PdCl₄ to give compounds of type [PdCl₂Lⁿ₂] for L¹, L² or L³ as monodentate nitrogen-donor ligands and chelated mononuclear complexes of the type [PdCl₂Lⁿ] for L⁴, L⁵, L⁶ or L⁷. The complexes of the monodentate azines L¹ and L² exist in solution as mixtures of isomers differing in the ligating nitrogens. The compounds L¹, L² and L⁴–L⁷ also reacted with [Pd₂Cl₄(PR₃)₂] to give [PdCl₂(PR₃)Lⁿ](n= 1, R₃= Me₂Ph or Me₂(C₆H₄OMe-4); n= 2, R₃= Me₂Ph, Me₂(C₆H₄OMe-4) or Ph₃; n= 4 or 5, R₃= Me₂Ph; n= 6, R₃= Buⁿ₃; n= 7, R₃= Buⁿ₃ or Me₂Ph), in which the ligands are monodentate, or [{PdCl₂(PR₃)}₂Lⁿ](Lⁿ= L⁴–L⁷, R₃= Me₂Ph), in which the ligands are bidentate bridging. The phosphine complexes were characterised in solution but were isolated only for [PdCl₂(PR₃)Lⁿ](Lⁿ= L⁶, R₃= Buⁿ₃; L⁷, R₃= Buⁿ₃ or Me₂Ph; L², R₃= Ph₃). Compounds L⁴, L⁶ or L⁷ reacted with the η³-methylallylpalladium complex [{PdCl(η³-CH₂CMeCH₂)}₂] and NH₄PF₆ to give [Pd(η³-CH₂CMeCH₂)Lⁿ] PF₆(Lⁿ= L⁴, L⁶ or L⁷). The crystal structure of [PdCl₂L⁶]·0.5CH₂Cl₂ was determined by X-ray diffraction analysis: the crystals are monoclinic, space group P2₁ with a= 9.5830(13), b= 13.9720(14) and c= 14.726(2)Å, β= 97.610(11)° and Z= 4. It shows two molecules of the complex in the asymmetric unit differing only in the torsion angles around the N–N bond.