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

Abstract

2-(Arylazo)pyrimidine ( p-R-C 6H 4–N N–C 4H 3N 2, aapm, R = H (papm, 3a), Me (tapm, 3b), Cl (Clpapm, 3c)) are N, N′-chelating ligands. Platinum(II) complexes, Pt(aapm)Cl 2 ( 4) have been synthesized by the reaction of K 2PtCl 4 and aapm in MeCN–water under refluxing condition. The reaction of Pt(aapm)Cl 2 with ArNH 2 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 ArNH 2 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)Cl 2. Cyclic voltammograms show two quasireversible azo reductions of Pt(aapm)Cl 2; 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.