Metal−Metal Interactions in Platinum(II)/Gold(I) or Platinum(II)/Silver(I) Salts Containing Planar Cations and Linear Anions

The salts [Pt{C(NHMe)2}4][Au(CN)2]2, [Pt{C(NHMe)2}4][Ag2(CN)3][Ag(CN)2], [Pt(en)2][Au(CN)2]2, [Pt(en)2][Ag(CN)2]2,
and [Pt(bipy)2][Au(CN)2]2 have been prepared by mixing solutions of salts containing the appropriate cation with
solutions of K[Au(CN)2] or K[Ag(CN)2]. Because the platinum atom in the cation is sterically protected, the structures
of [Pt{C(NHMe)2}4][Au(CN)2]2 and [Pt{C(NHMe)2}4][Ag2(CN)3][Ag(CN)2] reveal no close metal−metal interactions.
Colorless crystals of [Pt(en)2][Au(CN)2]2 and [Pt(en)2][Ag(CN)2]2 are isostructural and involve extended chains of
alternating cations and anions that run parallel to the crystallographic a axis, along with isolated anions. In the
chains, the metal−metal separations are relatively short:  Pt···Au, 3.1799(3) Å; Pt···Ag, 3.1949(2) Å. In [Pt(bipy)2][Au(CN)2]2, each cation has axial interactions with the anions through close Pt···Au contacts [3.1735(6) Å]. In
addition, the anions are weakly linked through Au···Au contacts of 3.5978(9) Å. Unlike the previously reported
Pt/Au complex [Pt(NH3)4][Au(CN)2]2·1.5H2O, which is luminescent, none of the salts reported here luminesce.