Synthesis of novel platinum-silver and platinum-copper complexes with bridging alkynyl ligands

The study of the reactivity of Pt₂M₄(CCR)₈] (M=Ag or cu; R=Ph or ^tBu) towards different neutral and anionic ligands is reported. This study reveals that reactions of the phenylacetylide derivatives Pt₂M₄(CCPh)₈] with anionic, X⁻ (X=Cl or Br) or neutral donors (CN^tBu or py) in a molar ratio 1:4 (m/donor ratio 1:1) yield the trinuclear anionic (NBu₄)₂{Pt(CCPh)₄ (MX)₂] (M=Ag or Cu, X =Cl or Br) or neutral {Pt(CCPh0₄=sAGL)₂] (L=CN^tBu or py) complexes, respectively. The crystal structure of (NBu₄)₂{Pt(CCPh)₄}(CuBr)₂](4) shows that the anion is formed by a dianionic Pt(CCPh)₄ fragment and two neutral CuBr units joined through bridging alkynyl ligands. All the alkynyl groups are σ bonded to Pt and η²-coordinated to a Cu atom which have an approximately trigonal-planar geometry. By contrast, similar reactions with Pt₂M₄(CC^tBu)₈] (molar ratio M/donor 1:1) afford hexanuclear dianionic (NBu₄)₂Pt₂M₄(CC^tBu)₈X₂] or neutral Pt₂Ag₄(CC^tBu0₈Py₂]. Only by treatment with a large exces of Br ⁻ (molar ratio M/Br⁻ 1:2) are the trinuclear complexes (NBu₄)₂{Pt(CC^tBu₄ (MBr)₂] (M=Ag, Cu) obtained. Attempted preparations of analogous complexes with phosphines (L′=PPh₃ or PEt₃) by reactions of Pt₂M₄(CCR₈] with L′ leads to displacement of alkynyl ligands from platinum and formation of neutral mononuclear complexes trans-Pt(CCR)₂L′₂].