Azolium-2-dithiocarboxylate cAAC Me -CS 2 : A Coordinatively Flexible, Redox-Active Ligand in Transition Metal Chemistry

The reactivity of the cyclic (alkyl)(amino)carbene (cAAC Me )-stabilized CS 2 adduct, the azolium-2-dithiocarboxylate cAAC Me -CS 2 ( 1 ), toward selected transition metal reagents is reported. Mono- or polynuclear (cluster) complexes [(Fe(CO) 3 (cAAC Me -CS 2 )] ( 2 ), [{CrCp(cAAC Me -CS 2 )} 2 ] ( 3 ), [Cr 3 (cAAC Me -CS 2 ) 4 (CO) 3 ] ( 4 ), [Re(cAAC Me -CS 2 ) 3 ][Re 2 (CO) 6 (μ 2 -Cl) 3 ] ( 5 ), and [Ni 2 Br 2 (cAAC Me -CS 2 ) 2 (cAAC Me -CS 3 )][NiBr 3 ] ( 6 ) were prepared and characterized. Solid state structural analysis, cyclic voltammetry, and spectroscopy revealed that the coordinated ligands 1 adopt multiple formal redox states in these complexes, ranging from 0 to −2. The cAAC Me -CS 2 ( 1 ) ligands were observed in a range of different terminal or bridging bonding modes, which feature metal coordination either exclusively via the sulfur atoms (κ S, κ S ′; μ 2 -κ 2 S, κ 2 S ′; μ 3 -κ 2 S, κ 2 S ′) or, for 4, in addition, via the carbon atom of the CS 2 group (μ 2 -κ 2 S, κ 2 S ′, κ C ). Furthermore, oxidative reaction conditions involving 1 led to C–S bond cleavage, which resulted in cyclic activation products (cAAC Me ) 2 (C 2 S 3 ) ( 7 ) and [(cAAC Me ) 2 (C 2 S 3 )][Br 3 ] ( 8 ), as well as the cAAC Me -CS 3 ligand in 6 . These findings provide evidence for the ligand systems’ unique adaptability and versatility in coordination modes as well as ligand redox states, proving carbene-CS 2 adducts to be most promising candidates for future endeavors into transition metal redox or cluster chemistry.