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

Abstract

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]BF 4 and AgBF 4 initially gives 1:1 mixed-metal complexes [Pt(dppf)(CCPh) 2Cu(NCMe)]BF 4 ( 2) and [Pt(dppf)(CCPh) 2Ag]BF 4 ( 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]BF 4 (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 and the Group 11 metal ion is bonded in an η 2-fashion to four carboncarbon triple bonds to afford heterometallic pentanuclear Fe 2Pt 2M 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.