New Tripodal Tridentate Ligands with {NS 2 } Donor Set and a Backbone Hydroxo Anchor, and Their Copper(I) and ­Copper(II) Complexes

A series of five tripodal tridentate ligands (HO)C[(CH 2 ) x NR 2 ](CH 2 SR) 2 (H L 1 –H L 5 ) with {NS 2 } donor set has been synthesized via an efficient two‐step protocol starting from 1, 3‐dichloroacetone. All five ligands bear a backbone hydroxo group that is available for further functionalization. The five ligands differ by the type of N‐donor (NR 2 = pyridine‐2‐yl or imidazol‐2‐yl), by the spacer between the backbone‐C and the N‐donor heterocycle ( x = 0, 1), and with respect to their topology, viz. whether two thioether‐S are part of a cyclic 1, 4‐dithiacycloheptane fragment or not (R = Et or –CH 2 –). Copper(I) and copper(II) complexes have been prepared and studied in solution (ESI‐MS, UV/Vis, and NMR spectroscopy in case of the copper(I) complexes) as well as in solid state (single‐crystal X‐ray diffraction of [(H L 2 )Cu(MeCN)] n (OTf) n , [(H L 3 )Cu(MeCN)](PF 6 ) and [(H L 5 )Cu(MeCN)] n (PF 6 ) n as well as [( L 4 ) 2 Cu 3 (MeCN) 3 ](PF 6 ) 2 and [( L 2 ) 2 Cu 2 Cl 2 ], [( L 3 ) 4 Cu 4 ](OTf) 4 , and [( L 4 ) 2 Cu 2 (MeCN) 2 ](OTf) 2 ; SQUID magnetometry of [( L 2 ) 2 Cu 2 Cl 2 ] and [( L 3 ) 4 Cu 4 ](OTf) 4 ,). The ligand scaffolds show ambidentate character depending on the metal ion oxidation state. All copper(I) ions are found in distorted tetrahedral environment comprising an {NS 2 } ligation of the tridentate ligand as well as an exogenous MeCN; either mononuclear complex cations or 1D polymeric structures are found. In case of all copper(II) complexes the backbone‐alcohol group is deprotonated and bridges two metal ions, giving dinuclear or tetranuclear species with antiferromagnetic coupling. The Cu–S bond lengths are found to vary significantly, which reflects the plasticity of the Cu‐thioether bond known from metalloproteins and synthetic analogs.