STRUCTURAL VARIATION IN SILVER ACETYLIDE COMPLEXES - SYNTHESES AND X-RAY STRUCTURE DETERMINATIONS OF [PH(3)PAGC-CPH](4)CENTER-DOT-3.5THF AND [ME(3)PAGC-CSIME(3)](INFINITY)

[Ph(3)PAgC=CPh](4) . 3.5THF (2) can be prepared by the reaction of CpA gPPh(3) (1) with lithium phenylacetylide (1:1 equiv), Similarly [Me(3) PAgC=CSiMe(3)]infinity (4) can be prepared by the reaction of CpAgPMe( 3) (3) and lithium (trimethylsilyl)acetylide (1:1 equiv). Both complex es have been characterized by elemental analyses, solid-state IR spect roscopy, H-1 and P-31 NMR spectroscopy, and low-temperature X-ray diff raction studies, The structure of 2 consists of a tetranuclear ''flat- butterfly'' core, with the two ''hinge'' silver atoms sigma-bonded to two acetylide fragments, which then pi-complex the apical Ag(PPh(3))(2 ) fragments, In 4, the smaller steric bulk of the phosphine employed a llows this complex to crystallize as a polymer, Rather than being cons tructed from simple [R(3)PAg(acetylide)] units, both 2 and 4 are forme d by the aggregation of(acetylideAg- and Ag(PR(3))(2)(+) fragments. Th e preparation of complexes 2 and 4 demonstrates the synthetic utility of nucleophilic substitution of CpAgPR(3) in the synthesis of Ag organ ometallics, The different structural alternatives adopted by 2 and 4 p oint to the steric bulk of the phosphine ligands being the major influ ence on the structure of Ag acetylide complexes.