Taking Solution Proton NMR to Its Extreme: Prediction and Detection of a Hydride Resonance in an Intermediate-Spin Iron Complex

Guided
by DFT based modeling the chemical shift range of a hydride
resonance in the proton nuclear magnetic resonance (NMR) spectrum
of the intermediate-spin, square planar iron complex tBu(PNP)­Fe–H was predicted and detected as
a broad resonance at −3560 ppm (295 K) with a temperature dependent
shift of approximately 2000 ppm between 223 and 383 K. The first detection
of a metal-bonded hydrogen atom by solution NMR in a complex with
a paramagnetic ground state illustrates the interplay of theory and
experiment for the characterization of key components in paramagnetic
base metal catalysis.