Promotion of tetrahedral copper(I) dimers by chelation of 1,1′-bis(diphenylphosphino)ferrocene (dppf). Crystal structures of [{Cu(μ-X)(dppf-P,P′)}2](X = O2CH, I or NO3)

Abstract

Treatment of Cu(NO3)2 with 1,1′-bis(diphenylphosphino)ferrocene (dppf) gave [{Cu(μ-NO3-O)(dppf-P,P′)}2] which readily exchanged with NaO2CH or KI to give [{Cu(μ-O2CH-O,O′)(dppf-P,P′)}2] or [{Cu(μ-I)(dppf-P,P′)}2]. X-Ray structural analysis of the complexes revealed three tetrahedral copper(I) dimers with nitrate, iodide or formate preferentially in bridging and dppf consistently in chelating modes. The P-Cu-P chelate angle in the nitrate [11 7.8(1)°] is the largest of known dppf chelates in all geometries. These structures are different from their triphenylphosphine analogues which are all monomers. Exchanges of the nitrate complex with other carboxylates gave [{Cu(μ-O2CR)(dppf-P,P′)}n] (R = Me, CF3, Et, Prn or Ph). It also reacted with a stoichiometric amount of dppf to give [Cu2(NO3-O)2(μ-dppf)(dppf-P,P′) 2]. The geometrical influence of PPh3, Ph2PCH2PPh2 and dppf, and their preferred bonding modes to Cu1 in relation to the complex nuclearity, are discussed.