Polynuclear platinum-silver, -copper, and -gold acetylide complexes. Molecular structure of [Pt₂Ag₄(C≡CBu^t)₈]

Hexanuclear complexes [Pt₂Ag₄(C≡CR)₈] [R = Ph (1) or Bu^t (2)] have been obtained by treating [PtCl₂(tht)₂] (tht = tetrahydrothiophene) with [Ag(C≡CR)]_n(Pt/Ag 1: 4). The complexes [Pt₂M₄(C≡CR)₈] [M = Cu, R = Ph (3) or Bu^t (4); M = Au, R = Bu^t (5)] were obtained from [Pt₂Ag₄(C≡CR)₈] with CuCl or [AuCl(tht)] respectively. Alternatively, the reactions between [NBu₄]₂[Pt(C≡CR)₄] and AgClO₄, CuCl-NaClO₄, or [AuCl(tht)]-NaClO₄ yield respectively complexes (1)-(5). The molecular structure of [Pt₂Ag₄(C≡CBu^t)₈] has been determined by an X-ray diffraction study: monoclinic, space group C₂ with a = 37.062(7), b = 12.0223(16), c = 20.459(3) Å, β = 107.485(15)°, Z = 6, R 0.0416, R′ 0.0465 for 5 613 reflections with F > 6σ(F). The six metal atoms are arranged in a slightly irregular octahedron with the platinum atoms mutually trans and the silver atoms in the equatorial plane, with Pt ⋯ Ag and Ag ⋯ Ag distances longer than 3.0 Å. Each platinum atom is in an almost square-planar environment formed by four C≡CBu^t ligands. Each acetylenic fragment also forms an asymmetric π interaction with one silver atom of the equatorial positions so that each silver atom is bonded to two acetylenic fragments, of two different Pt(C≡CBu^t), moieties. These moieties of each [Pt₂Ag₄(C≡CBu^t)₈] unit are staggered.