Tuning electronic structure through halide modulation of mesoionic carbene cobalt complexes

The first examples of Co(ii) mesoionic carbene complexes ((CoX2MIC2)-M-Dipp; X = Cl-, Br-, I-) demonstrate a new electronic perturbation on tetrahedral Co(ii) complexes. Using absorption spectroscopy and magnetometry, the consequences of the MIC's strong sigma-donating/minimal pi-accepting nature are analyzed and shown to be further tunable by the nature of the coordinated halide.