Reaction of platinum(II) diamine and triamine complexes with selenomethionine

We have reacted [Pt(dien)Cl]Cl, [Pt(en)(D(2)O)(2)](2+), and [Pt(Me(4)en)(D(2)O)(2)](2+) [Me(4)en = N,N,N',N'-tetramethylethylenediamine] with selenomethionine (SeMet). When [Pt(dien)Cl]Cl is reacted with SeMet, [Pt(dien)(SeMet-Se)](2+) is formed; two Se-CH(3) resonances are observed due to the different chiralities at the Se atom upon platination. In a reaction of [Pt(dien)Cl]Cl with an equimolar mixture of SeMet and Met, the SeMet product forms more quickly though a slow equilibrium with approximately equal amounts of both products is reached. [Pt(Me(4)en)(D(2)O)(2)](2+) reacts with SeMet to form [Pt(Me(4)en)(SeMet-Se)(D(2)O)](2+) initially but forms [Pt(Me(4)en)(SeMet-Se,N)](+) ultimately. One stereoisomer of the chelate, assigned to the R chirality at the Se atom, dominates within the first few minutes of reaction. [Pt(en)(D(2)O)(2)](2+) forms a variety of products depending on reaction stoichiometry; when one equivalent or less of SeMet is added, the dominant product is [Pt(en)(SeMet-Se,N)](+). In the presence of excess SeMet, [Pt(en)(SeMet-Se)(2)](2+) is the dominant initially, but displacement of the en ligand occurs leading to [Pt(SeMet-Se,N)(2)] as the eventual product. Displacement of the en ligand from [Pt(en)(SeMet-Se,N)](+) does not occur. In reactions of K(2)PtCl(4) with two equivalents of SeMet, [Pt(SeMet-Se,N)(2)] is formed, and three sets of resonances are observed due to different chiralities at the Se atoms. Only the cis geometric isomers are observed by (1)H and (195)Pt NMR spectroscopy.