Study of Pt(II)-cyclic amines complexes of the types cis- and trans-Pt(amine) 2I 2 and cis- and trans-Pt(amine) 2(NO 3) 2 and their aqueous products by

Abstract

Complexes of the types cis- and trans-Pt(amine) 2I 2 containing cyclic amines were synthesized and studied mainly by IR and multinuclear NMR spectroscopies. The compounds were converted to cis- and trans-Pt(amine) 2(NO 3) 2, which were also investigated. The hydrolysis and the aquation reactions of the latter compounds were then studied in D 2O in different conditions of pH. In acidic medium, the aqueous product is [Pt(amine) 2(D 2O) 2] 2+ and for a few amines, [Pt(amine) 2(D 2O)(NO 3)] + was detected. In basic pH, the main product is Pt(amine) 2(OD) 2 and Pt(amine) 2(OD)(NO 3) was detected for several compounds. In neutral pH, the cis isomers form between two and four species in fresh solutions. The most shielded species in 195Pt NMR is the monoaqua–monohydroxo complex cis-[Pt(amine) 2(D 2O)(OD)] + and the less shielded compound is the dihydroxo-bridged dimer [Pt(amine) 2(μ-OD) 2Pt(amine) 2] 2+, which were observed for all the compounds. For a few amines, the monohydroxo-bridged dimer [Pt(D 2O)(amine) 2(μ-OD)Pt(OD)(amine) 2] 2+ was detected and for cyclohexylamine, a fourth signal was assigned to a cyclic hydroxo-bridged trimer [(Pt(amine) 2(μ-OD)) 3] 3+. 195Pt NMR spectroscopy has shown that the concentration of the monomer decreases with time, while the concentration of the dimers increases. Only one product was observed for the trans isomers in neutral pH. The signal was assigned to the monoaqua–monohydroxo species trans-[Pt(amine) 2(D 2O)(OD)] +. The 13C and 1H NMR spectra of most of the complexes were measured. All the coupling constants 2,3 J( 195Pt– 1H) and 2,3 J( 195Pt– 13C) are larger in the cis compounds than in the trans isomers.