Cyclometalation of Arylazo Compounds. Part 1 synthesis and cyclopalladation of some substituted 1‐arylazonaphthalenes. 1st Communication on compounds with a metal‐arene σ‐bond

The syntheses of 1‐phenylazonaphthalene (1a) and its [3′‐methyl‐ (1b), 4′‐methoxy‐ (1c), 3′‐methoxy‐ (1d)] derivatives are described. Cyclopalladation of these azo ligands with Pd(II) acetate or Na2PdCl4 leads to complexes with Pd(II) coordinated on the azo Nβ‐atom and a PdC σ‐bond at C(2) in the naphthalene moiety. The preference of Pd(II) for this type of metalation at C(2) over the palladation at the ortho positions of the phenyl ring or at the peri position of the naphthyl ring is believed to be largely due to steric effects and the different reactivities of the two arene moieties. Substitution of the acetato‐bridge with bromide or iodide allows the syntheses of the corresponding bromo‐ and iodo‐bridged complexes, and a chloro‐bridged dimer complex can be converted to a monomeric ethylenediamino‐Pd(II)‐azo species with ethylenediamine. Cyclopalladation of sulfonated azo ligands leads to water‐soluble Pd(II) complexes with a Pd‐C σ‐bond at C(2).