SYNTHESIS OF ANIONIC PENTAFLUOROPHENYL PLATINUM-SILVER ACETYLIDE COMPLEXES - MOLECULAR-STRUCTURES OF (NBU4)[PT(C6F5)2(MU-CCPH)2AG(PPH3)] AND (NBU4)2[(PT(C6F5)2(MU-CCPH)2AG)2(MU-DPPE)]

Heterobinuclear alkynyl-bridged complexes (NBU4)[Pt(C6F5)2(mu-C=CR)2AgL] (R = Ph or (t)Bu; L = PPh3 or PEt3) (1-4) are obtained by treating the anionic tetranuclear platinum-silver derivatives (NBU4)2[Pt2Ag2(C6F5)4(C=CR)4] (R = Ph or (t)Bu) with PPh3 or PEt3 (molar ratio 1:2 or 1:4), whereas treatment with the bidentate 1,2-bis(diphenylphosphino)ethane (dppe) (molar ratio 1:1) gives tetranuclear complexes (NBu4)2[{Pt(C6F5)2(mu-C=CR)2Ag}2(mu-dppe)] (R = Ph 5; R = (t)Bu 6). The structures of (NBU4)[Pt(C6F5)2(mu-C=CPh)2AgPPh3] (1) and (NBU4)2[{Pt(C6F5)2(mu-C=CPh)2Ag)2(mu-dppe)] (5) have been established by single-crystal X-ray diffraction studies. In the solid state, the structure of the anion of complex 1 reveals that the two metal atoms [Pt ... Ag 3.059(l) angstrom] are asymmetrically bridged by two phenylacetylide groups, each of which forms a sigma-bond to platinum and a side-on pi-bond to silver. The anion of compound 5, which possesses an inversion centre, is formed by two identical {Pt(C6F5)2(mu-C=CPh)2Ag) units connected through a dppe ligand. Each silver atom is asymmetrically pi-bonded to each acetylide group and completes their trigonal coordination by bonding to a phosphorus atom of the dppe. H-1, F-19, P-31 NMR data indicate that all complexes exhibit dynamic behaviour in solution.