Azolium-2-dithiocarboxylate cAACMe-CS2: A Coordinatively Flexible, Redox-Active Ligand in Transition Metal Chemistry
Martin Simon Luff1, Celine Sophie Corsei1, Ivo Krummenacher1,2
1Institute for Inorganic Chemistry, Julius-Maximilians-Universität Würzburg, Am Hubland, Würzburg 97074 Germany.
Abstract:
The reactivity of the cyclic (alkyl)(amino)carbene (cAACMe)-stabilized CS2 adduct, the azolium-2-dithiocarboxylate cAACMe-CS2 (1), toward selected transition metal reagents is reported. Mono- or polynuclear (cluster) complexes [(Fe(CO)3(cAACMe-CS2)] (2), [{CrCp(cAACMe-CS2)}2] (3), [Cr3(cAACMe-CS2)4(CO)3] (4), [Re(cAACMe-CS2)3][Re2(CO)6(μ2-Cl)3] (5), and [Ni2Br2(cAACMe-CS2)2(cAACMe-CS3)][NiBr3] (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 cAACMe-CS2 (1) ligands were observed in a range of different terminal or bridging bonding modes, which feature metal coordination either exclusively via the sulfur atoms (κS, κS'; μ2-κ2S, κ2S'; μ3-κ2S, κ2S') or, for 4, in addition, via the carbon atom of the CS2 group (μ2-κ2S, κ2S', κC). Furthermore, oxidative reaction conditions involving 1 led to C-S bond cleavage, which resulted in cyclic activation products (cAACMe)2(C2S3) (7) and [(cAACMe)2(C2S3)][Br3] (8), as well as the cAACMe-CS3 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-CS2 adducts to be most promising candidates for future endeavors into transition metal redox or cluster chemistry.
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