Aggregation control of copper(I) thiolates through substituent size and ancillary chelate ligands: closely related mono-, di-, tri- and tetranuclear complexes

The choice of thiolates and of ancillary nitrogen chelate ligands N∧N determines the aggregation state of copper(I) thiolate compounds [(RS)xCuy(N∧N)z]k. Starting from electrogenerated [(RS)Cu]n, the species obtained and structurally characterized include (i) mononuclear (RS)Cu(Me4phen), Me4phen=3,4,7,8-tetramethyl-1,10-phenanthroline, with 2,6-diorganophenyl thiolates RS−, (ii) dinuclear [(μ-RS)Cu(Me2phen)]2, Me2phen=2,9-dimethyl-1,10-phenanthroline, with R=phenyl or o-tolyl, (iii) trinuclear (μ-RS)3Cu3(Me4phen)2 with R=mesityl, (iv) tetranuclear (μ-RS)4Cu4(bpy)2 with R=2,4,6-i-Pr3C6H2, and (v) the tetranuclear dianion [(μ-RS)6Cu4]2− where the added chelate ligand N∧N=bis(2-imidazolyl)ketone occurs in the [(N∧N)2Cu]+ counterions. The new trinuclear (μ-MesS)3Cu3(Me4phen)2 exhibits an unsymmetrical Cu3S3 six-membered ring in which the dicoordinate copper(I) center has a nearly linear configuration (angle SCuS 173.93(13)°). Both tetracoordinate copper(I) atom sites exhibit a characteristic distortion from a tetrahedral towards a trigonal pyramidal CuN2S2 arrangement which is reminiscent of the geometry observed for the rhombic variants of type 1 Cu centers in blue copper proteins.