[Pt(C⋮CR)4]2- as Double Alkynylation Reagents: Facile Formation of Binuclear Bis(μ-alkynide) (M−Pt) and Unsymmetrical Trinuclear Double Bis(μ-alkynide) (M−Pt−Pt) Complexes

Treatment of (NBu 4 ) 2 [Pt(C⋮CR) 4 ]·2H 2 O (R = t -Bu, 1a; SiMe 3, 1b; Ph, 1c ) with 1 equiv of the dicationic solvento species [Cp*M(PEt 3 )(acetone) 2 ](ClO 4 ) 2 (M = Rh, Ir) results in double alkynyl transfer to give the binuclear compounds [(PEt 3 )Cp*M(μ-1κ C α:η 2 -C⋮CR) 2 Pt(C⋮CR) 2 ] (M = Rh, 2; Ir, 3 ), in which the organometallic unit “ cis -Pt(C⋮CR) 2 ” is unusually stabilized by η 2 -bis(alkyne) interactions, as has also been confirmed for the related binuclear complex [(PPh 3 )Cp*Rh(μ-1κ C α:η 2 -C⋮CSiMe 3 ) 2 Pt(C⋮CSiMe 3 ) 2 ], 4b, which has been prepared analogously. These binuclear tetraalkynyl complexes can be used as precursors to unusual bis(double-alkynide)-bridged trinuclear derivatives [(PEt 3 )Cp*M(μ-1κ C α:η 2 -C⋮CR) 2 Pt(μ-2κ C α:η 2 -C⋮CR) 2 Pt(C 6 F 5 ) 2 ] (M = Rh, 5; Ir, 6 ) by displacement reactions of thf from [ cis -Pt(C 6 F 5 ) 2 (thf) 2 ]. An X-ray diffraction study confirms that in complex 5b (R = SiMe 3 ) the mononuclear rhodium fragment “Cp*Rh(C⋮CSiMe 3 ) 2 (PEt 3 )” acts as a chelating bidentate ligand toward the alkynyl-bridged diplatinum organometallic unit Pt(μ-1κ C α:η 2 -C⋮CSiMe) 2 Pt(C 6 F 5 ) 2 .