A DFT mechanistic study of the synthesis of trans-Z,Z-[PtIICl(NH3){HN = C(NH2)Me}2]Cl from addition of NH3 to trans-[PtIICl2(N CMe)2]

Abstract

The reaction mechanism between trans-[PtIICl2(N^CMe)2] and ammonia to give trans-Z,Z-[PtIICl(NH 3) {HN = C(NH2)Me}2]Cl has been studied at DFT level. Results showed that, in dichloromethane solution at 263.15 K, the chloride substitution by the ammonia on platinum is a process kinetically more favoured than the ammonia nucleophilic addition to the nitrile of about three orders of magnitude, and hence the nucleophilic addition reaction occurs after. Finally, both nucleophilic addition steps are geometrically driven to give products in the E configuration even if the final products were experimentally observed in the Z configuration. For trans- Z,Z-[PtIICl(NH3)(N^CMe)2, the isomerization mechanism has been investigated for both nucleophilic addition steps by considering the deprotonation → isomerization → protonation sequence on nitrogens. The deproto- nation steps could involve either the coordinated or the aminic nitrogen of the formed amidine. Outcomes indicated that the path involving the deprotonation of the aminic nitrogen is favoured.