Coupling of arylamine with coordinated arylazopyrimidine in platinum(II) complexes. Single crystal X-ray structure, spectra and electrochemistry

2-(Arylazo)pyrimidine (p-R-C6H4–NN–C4H3N2, aapm, R = H (papm, 3a), Me (tapm, 3b), Cl (Clpapm, 3c)) are N,N′-chelating ligands. Platinum(II) complexes, Pt(aapm)Cl2 (4) have been synthesized by the reaction of K2PtCl4 and aapm in MeCN–water under refluxing condition. The reaction of Pt(aapm)Cl2 with ArNH2 in MeCN has synthesized C–N coupled product, Pt(aapm-N–Ar)Cl (5–10). The single crystal X-ray structure determination of one of the compounds has suggested the coupling of ArNH2 at ortho-C–H of the pendant aryl part of aapm in the chelated complex. The stereochemistry and the bonding are described by 1H NMR data. The solution electronic spectra of Pt(aapm-N–Ar)Cl exhibit multiple transition at Vis–NIR region (500–1250 nm) which are absent in Pt(aapm)Cl2. Cyclic voltammograms show two quasireversible azo reductions of Pt(aapm)Cl2; Pt(aapm-N–Ar)Cl exhibit four successive redox couples, one of them (positive to SCE) is oxidative in nature and other (negative to SCE) are ligand reductions.

Graphical abstractDichloro platinum(II) complexes of 2-(arylazo)pyrimidine and their reaction with aromatic amines are described in this work. One of the reaction products has been confirmed by X-ray diffraction study. The spectral and electrochemical results have been correlated with MO calculation.Figure optionsDownload full-size imageDownload as PowerPoint slide