Isolation of polynuclear platinum complexes in the ammination reaction of activated olefins. X-Ray crystal structure of a diplatinum(II) perchlorate salt bridged by an ammoniodiethylide group

Abstract

By reaction of secondary and primary amines and ammonia with the cationic complex [Pt(η²-C₂H₄)Cl(Me₄en)]⁺, (1)(Me⁴en =NNN′N′-tetramethylethylenediamine), bi-, tri-, and tetra-metallated ammonium ions of formula [{Pt(C₂H₄)Cl(Me₄en)}_n(NR_{4 –n})]⁺(n= 2, 3, and 4, respectively) have been obtained. The enhanced electrophilicity of η²-ethene in (1), and the absence of a formal negative charge on platinum in the addition products, stabilizing the Pt–C σ bond, play a key role in the synthesis of such species. These compounds undergo acidolysis to give polyalkylated ammonium ions. The crystal and molecular structure of the salt [{Pt(C₂H₄)Cl(Me₄en)}₂(NEt₂)][ClO₄] has been determined by X-ray diffraction. The compound crystallizes in the monoclinic space group C2/c with Z= 8 in a unit cell of dimensions a= 30.38(2), b= 8.55(1), c= 25.26(2)Å, and β= 111.0(1)°. The structure was solved by Patterson and Fourier methods and refined by full-matrix least squares to R= 0.067 for 2 817 independent reflections. In the cation the two Pt atoms are bridged by a 3,3-diethyl-3-azoniapentane, with a chlorine and two nitrogen atoms from a chelating Me₄en ligand completing the square-planar co-ordination around each metal atom.