Synthesis, characterization and structural studies of new heterometallic alkynyl complexes of platinum and Group 11 metals with chelating bis(diphenylphosphino)ferrocene ligand

Reaction of the platinum bis(alkynyl) complex [Pt(dppf)(C ≡ CPh)2] (1) (dppf = bis(diphenylphosphino)ferrocene) with an equimolar amount of Group 11 metal salts [Cu(NCMe)4]BF4and AgBF4initially gives 1:1 mixed-metal complexes [Pt(dppf)(C ≡ CPh)2Cu(NCMe)]BF4(2) and [Pt(dppf)(C ″ CPh)2Ag]BF4(3) in good yields. Upon standing in solution at room temperature, compounds 2 and 3 rearrange and aggregate to the corresponding diplatinum complexes [{Pt(dppf)(C ≡ CPh)2}2M]BF4(M = Cu (4), Ag (5)) which exhibit an intense molecular ion envelope for the respective cation in their electrospray mass spectra. Compounds 4 and 5 can also be formed when the reaction is performed using a 2:1 molar ratio of 1 and the Group 11 salts. The X-ray crystal structures of 1, 4 and 5 have been determined. Structures of 4 and 5 reveal that the two square-planar platinum coordination planes in the cation are approximately orthogonal an 2-fashion to four carbon-carbon triple bonds to afford heterometallic pentanuclear Fe2Pt2M complexes (M = Cu, Ag) in which each platinum center is stabilized by a dppf ligand. Each of the new complexes displays a reversible oxidation couple corresponding to the ferrocenyl unit of dppf and there is less stabilization of the silver in the mixed-metal complex than in the copper congeners.