“…The solid-state IR spectrum of 4 shows three absorption bands at ν = 2137, 2094, and 2064 cm -1 for two CNtBu ligands at a rhodium(I) complex. [22][23][24] Spectra measured in toluene and THF also reveal three bands at ν = 2137, 2095, and 2061 cm -1 (toluene) and at ν = 2139, 2096, and 2061 cm -1 (THF). However, DFT calculations to model the IR spectrum of 4 in the gas phase show only two absorption bands at ν = 2189 and 2133 cm -1 (B3LYP/cc-pvdz).…”