Copper( I ) Complexes with a Cu 4 S 6 ‐ and CuS 4 ‐Type Core Obtained from the Reaction of Copper(0) with HN(SPPh 2 ) 2 ·I 2

The copper( I ) compounds [Cu I 4 (L) 3 ]I 3 ( 1 ) and [Cu I (HL) 2 ]I 3 · CH 3 CN ( 2 ) [HL = HN(SPPh 2 ) 2 ] have been obtained from the reaction of the adduct HL · I 2 with copper(0) powder in diethyl ether solution. Compound 1 contains a tetrahedron of Cu atoms with three anionic L ligands coordinated to the coppers through the sulfur atoms to build a Cu 4 S 6 core. The mean Cu–Cu and Cu–S bond lengths related to the Cu 4 S 6 core in copper‐loaded transcription factors CuAce1 and CuMac1, and in the model compound [Cu 4 (SPh) 6 ] 2– , have been compared with those of the [Cu 4 (L) 3 ] + cation, and the geometric volumes of the Cu 4 cores have been evaluated. The results suggest that the cation [Cu 4 (L) 3 ] + is a possible structural model compound for the metal site in Ace1 and Mac1 transcription factors. In compound 2 , two neutral HL ligands bind a Cu I ion in an S , S′ ‐isobidentate chelating fashion to form a slightly distorted tetrahedral CuS 4 core. The 31 P NMR spectroscopic data of compound 1 are consistent with the maintenance of its structure in solution. Moreover, phosphorus variable‐temperature measurements indicate a change from a two‐spin coupled AB system at 0 °C to an A 2 spin system at 40 °C. The reaction of [Cu 4 (L) 3 ] + with HI, monitored by 31 P NMR spectroscopy, leads to the protonation of the complexed ligands at the Cu 4 core and formation of the cation [Cu 4 (HL) 3 ] 4+ . The protonation reaction is reversible: increasing the amount of organic base 1,8‐bis(dimethylamino)naphthalene (DMAN) regenerates the starting cation [Cu 4 (L) 3 ] + .(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)