Exploiting a C–F Activation Strategy to Generate Novel Tris(pyrazolyl)methane Ligands

Two new tris(pyrazolyl)methane (Tpm) ligands were obtained by exploiting a C–F activation strategy. The novel monotopic ligand, H₂NPh(CF₃)(CPz₃), was utilized to generate a Mn-carbonyl complex. These compounds were characterized by NMR, IR, elemental analysis, X-ray crystallography, and DFT in the case of the Mn-compound. Of the computational levels of theory tested, we found that the TPSSh, B3PW91, and B3LYP functionals with the 6-311++G(d,p) basis set gave results closest to experimental data. When compared to a previously reported Mn-carbonyl compound, TpmMn(CO)₃]PF₆], our species, H₂NPh(CF₃)(CPz₃)Mn(CO)₃]PF₆], exhibited similar spectroscopic properties e.g., ν(C≡O) stretching]. This indicates that the presence of the H₂NPh(CF₃) group on the backbone of the Tpm ligand imposes little to no electronic influence on the metal center relative to the parent Tpm complex. Our novel ligand also provides a new spectroscopic handle to study Tpm derivatives, i.e., fluorine atoms for ¹⁹F-NMR spectroscopy.