Reactions of (σ-Alkynyl)platinum Complexes with [Pd(η³-C₃H₅)Cl]₂. Synthesis of Bis(η²-alkyne)(η³-allyl)palladium(II) Complexes. Crystal and Molecular Structure of [cis-(PPh₃)₂Pt(μ-η¹:η²-C⋮CtBu)₂Pd(η³-C₃H₅)](ClO₄)

The σ-bis and tetraalkynyl anions [ cis -Pt(C 6 F 5 ) 2 (C⋮CR) 2 ] 2 - and [Pt(C⋮CR) 4 ] 2 - (R = Ph, t Bu, SiMe 3 ) have been shown to be useful reagents for the formation of bis(μ-alkynyl) complexes via halide displacement reactions. They thus react with {[Pd(η 3 -C 3 H 5 )Cl] 2 } in a 2:1 molar ratio to form anionic heterobinuclear zwitterionic Q[ cis -(C 6 F 5 ) 2 Pt(μ-η 1:η 2 -C⋮CR) 2 Pd(η 3 -C 3 H 5 )] (Q = PMePh 3, R = Ph; Q = NBu 4, R = t Bu, SiMe 3 1a − c ) and (NBu 4 )[(RC⋮C) 2 Pt(μ-η 1:η 2 -C⋮CR) 2 Pd(η 3 -C 3 H 5 )] (R = Ph, t Bu, SiMe 3 2a − c ) complexes. The corresponding trinuclear 1:2 neutral adducts {[Pt(C⋮CR) 4 ][Pd(η 3 -C 3 H 5 )] 2 } (R = Ph, t Bu, SiMe 3 3a − c ) were formed by the addition of 1 equiv of the tetraalkynyl anions to {[Pd(η 3 -C 3 H 5 )Cl] 2 }. Binuclear derivative analogue [(PPh 3 ) 2 Pt(μ-η 1:η 2 -C⋮CR)Pd(η 3 -C 3 H 5 )](ClO 4 ) (R = Ph, t Bu 4a, b ) were produced by the reaction of {[Pd(η 3 -C 3 H 5 )Cl] 2 } with neutral [ cis -Pt(PPh 3 ) 2 (C⋮CR) 2 ] (1:2 ratio) in the presence of NaClO 4 (excess). The heterobimetallic anionic 1c (R = SiMe 3 ) and cationic 4b (R = t Bu) complexes were characterized by X-ray diffraction. In both, the two bridging alkynyl ligands remained σ bonded to the platinum center and η 2 coordinated to the palladium one.