Conversion of acetonitrile into acetamide in the co-ordination spheres of cis- and trans-MII(amine)2(M = Pt or Pd). Solution and crystal structural studies

Abstract

The preparation and solution behaviour of mono- and bis-acetonitrile complexes of cis-[Pt(NH₃)₂Cl₂], [Pt(en)Cl₂](en = ethane-1,2-diamine) and trans-[Pt(NH₃)₂Cl₂] has been investigated. The nitrile complexes are hydrolysed to acetamidate, acetamidate-bridged and mixed acetamidate–acetonitrile species. It is shown that an essential feature of monomeric acetamidate complexes with cis configuration is their tendency to dimerize to dinuclear platinum compounds having bridging amidate ligands. The resulting dinners undergoa facile head-to-tail to head-to-head rearrangement without any detectable intermediate. Solution studies of the mononitrile complex trans-[Pt(NH₃)₂(MeCN)(OH)]⁺ at around neutral pH reveal the formation of trans-[Pt(NH₃)₂(MeCN)(NHCOMe)]⁺, suggesting a preceding ligand exchange. The reactions of platinum with MeCN are compared with those of the kinetically labile palladium. The nitrile complex cis-[Pt(NH₃)₂(MeCN)Cl]ClO₄ and the mixed-ligand complex trans-[Pt(NH₃)₂(MeCN)(NHCOMe)]ClO₄ were characterized by X-ray crystallography: cis-[Pt(NH₃)₂-(MeCN)Cl]ClO₄, monoclinic, space group P2₁/c, a= 10.618(10), b= 10.625(8), c= 9.176(7)Å, β= 111.20(6)°, Z= 4; trans-[Pt(NH₃)₂(MeCN)(NHCOMe)]ClO₄, monoclinic, space group P2₁/c, a= 8.601 (6), b= 19.508(19), c= 7.625(4)Å, β= 11 5.29(5)°, Z= 4.