Metal-mediated and solvent dependent chlorination of the nitrosonaphtholato ligand

Abstract

Reaction of K[PtCl₃(Me₂SO)] and 1,2-naphthoquinone-1-monoxime in water–dimethyl sulfoxide medium led to cis-(S,N)-[PtCl{2-(O)C₁₀H₆NO}(Me₂SO)] 1. Chlorination of the latter in methanol readily generates, under mild conditions, the platinum(IV) compound cis-(S,N)-[PtCl₃{2-(O)C₁₀H₅Cl₂(OMe)NO}(Me₂SO)] 2 with a chelating nitrosonaphtholato ligand bearing a new chiral atom due to concomitant chlorination and nucleophilic addition of a MeOH solvent molecule. The newly formed ligand was liberated from 2 by reaction with excess thiourea. The chlorination course is strongly dependent on the nature of solvent employed and in CHCl₃ also at room temparature the chlorination with either Cl₂ or NOCl brings about only oxidation of the metal center to achieve cis-(S,N)-[PtCl₃{2-(O)C₁₀H₆NO}(Me₂SO)] 3. All complexes were characterized by C, H, N, Cl and Pt elemental analyses, FAB⁺ mass-spectrometry, IR and ¹H, ¹³C{¹H} and ¹⁹⁵Pt NMR spectroscopies, and 2 and 3 by X-ray crystallography which indicates the chelating bidentate ligand adopts the nitroso form.