Transition-metal–carbon bonds. Part 46. Cyclopalladation and cycloplatination of N-alkyl-N-nitrosoanilines

Abstract

N-methyl-N-nitrosobenzylamine (Q) is not cyclo-(ortho-)palladated by Na₂[PdCl₄] but gives a complex of type [PdCl₂O₂]. In contrast N-Methyl-N-nitrosobenzylamine is readily ortho palladated to give the chloro-bridged complex [[graphic omitted]₆H₄}CI₂](4a). This was converted into a mononuclear acetylacetonate (5a) and into species [[graphic omitted]₆H₄}ClL], L = PPh₃( crystal structure determined), PMe₂Ph, or pyridine, (6a), (6b), or (6c) respectively. With two moles of PPh₃ per palladium the Pd–NO bond is broken giving the σ-aryl species [Pd{C₆H₄N(NO)CH₃}Cl(PPh₃)₂](7a), the crystal structure of which has also been determined. With 1,2-bis(diphenylphosphino)ethane (dppe), (4a) gives the ion [[graphic omitted]₆H₄}(dppe)]+ isolated as its tetraphenylborate salt (8a). Some palladated derivatives of N-ethyl-N-nitrosoaniline and (4-methoxy)-N-methyl-N-nitrosoaniline were made similarly. With K₂[PtCl₄]N-methyl-N-nitrosoaniline gives a red material which was not obtained pure but which gave a mononuclear acetylacetonate [[graphic omitted]₆H₄}(acac)](5c) and bis-phosphine complex [Pt{C₆H₄N(NO)CH₃}Cl(PPh₃)₂](7d) analogous to the palladium complex. N-Ethyl-N-nitrosoaniline reacted similarly. Crystals of (6a) are triclinic, space group P, with a= 9.990(2), b= 15.195(3), c= 9.276(2)Å, α= 104.05(2), β= 97.92(2), γ= 89.47(2)°, and Z= 2. Those of (7a) are monoclinic, space group P2₁/c, with a= 12.047(2), b= 21.794(4), c= 16.402(2)Å, β= 108.54(1)°, and Z= 4. Both compounds crystallise with a molecule of CH₂Cl₂. Least-squares refinements gave final R values of 0.089 for (6a) and 0.083 for (7a).