Structure and Magnetization Dynamics of Dy−Fe and Dy−Ru Bonded Complexes

We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy 3+ ) and either a first‐row (Fe) or a second‐row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp 2 2− (PyCp 2 2− =[2,6‐(CH 2 C 5 H 3 ) 2 C 5 H 3 N] 2− ) facilitates the isolation and characterization of PyCp 2 Dy−FeCp(CO) 2 ( 1 ; d (Dy–Fe)=2.884(2) Å) and PyCp 2 Dy−RuCp(CO) 2 ( 2 ; d (Dy–Ru)=2.9508(5) Å). Computational and spectroscopic studies suggest strong TM→Dy bonding interactions. Both complexes exhibit field‐induced slow magnetic relaxation with effectively identical energy barriers to magnetization reversal. However, in going from Dy−Fe to Dy−Ru bonding, we observed faster magnetic relaxation at a given temperature and larger direct and Raman coefficients, which could be due to differences in the bonding and/or spin–phonon coupling contributions to magnetic relaxation.