Structural variation in silver acetylide complexes: syntheses and X-ray structure determinations of [Ph3PAgC≡CPh]4.3.5THF and [Me3PAgC≡CSiMe3]

[Ph3PAgC⋮CPh]4·3.5THF (2) can be prepared by the reaction of CpAgPPh3 (1) with lithium phenylacetylide (1:1 equiv). Similarly [Me3PAgC⋮CSiMe3]∞ (4) can be prepared by the reaction of CpAgPMe3 (3) and lithium (trimethylsilyl)acetylide (1:1 equiv). Both complexes have been characterized by elemental analyses, solid-state IR spectroscopy, 1H and 31P NMR spectroscopy, and low-temperature X-ray diffraction studies. The structure of 2 consists of a tetranuclear “flat-butterfly” core, with the two “hinge” silver atoms σ-bonded to two acetylide fragments, which then π-complex the apical Ag(PPh3)2 fragments. In 4, the smaller steric bulk of the phosphine employed allows this complex to crystallize as a polymer. Rather than being constructed from simple [R3PAg(acetylide)] units, both 2 and 4 are formed by the aggregation of (acetylide)2Ag- and Ag(PR3)2+ fragments. The preparation of complexes 2 and 4 demonstrates the synthetic utility of nucleophilic substitution of CpAgPR3 in the synthesis of Ag organometallics. T...