Synthesis, Characterization and Crystal Structure of the Water Soluble Copper(I) Complex with Trisulfonated Triphenylphosphine

Aqueous soluble copper(I) complexes stable towards valence disproportionation are rare.1 Thus, in addition to the seminal complex [Cu(NH3)3]+ isolated in 1901 by G. Bodlaender2 and recently reinvestigated by Lamble et al.,3 only salts of [Cu(CN)3]2- 4 and of [Cu(DMP)2]+ (DMP = 2,9-dimethyl-1,10-phenantroline)5 appear to have been isolated and characterized as solid species. On the contrary, a plethora of lipophilic CuI complexes have been synthesized and thoroughly investigated in organic media.6 In this connection, it may be noticed that the availability of water- and air-stable, soluble copper(I) complexes featured by a substantial coordinative unsaturation, might provide valuable starting compounds for developing an aqueous inorganic and bio-inorganic chemistry of copper(I), barely explored so far.1,7 Tris(m-sulfonatophenyl)phosphine (TPPTS) trisodium salt is a soft ligand whose coordination ability towards a variety of transition metals has been demonstrated by Herrmann et al. in the late eighties.8 Syntheses performed in aqueous media include metal centers such as MnI, Fe0, RuII, CoI,0, RhI, IrI, Ni0, Pd0, PtII,0, AgI and AuI, but not CuI. In the frame of our ongoing interest for CuI/CuII coordination chemistry with phosphines, phosphine oxides and chalcogenides, and phosphino-amines,9-16 we report here on the synthesis and characterization, including the X-ray structure, of the complex {Na5[Cu(TPPTS)2].5H2O.½EtOH}n, 1.½EtOH, where TPPTS is [P(C6H4-m-SO3)3]3-. For the synthesis we have utilized a two-phase approach, taking advantage of the lability of the [Cu(MeCN)4]+ precursor and of the capability of TPPTS to extract the copper ion into the aqueous phase through the formation of a very stable complex, which combines high water solubility with unusual redox stability.