The syntheses, structural, and magnetic characterization of three new organometallic Ce complexes stabilized by PyCp22- (PyCp22- = [2,6-(CH2C5H3)2C5H3N]2-) are reported. Complex 1 provides the first example of a crystallographically characterized unsupported Ce-Fe bond in a molecular compound. Results from IR spectroscopy and computational analyses suggest weaker Fe → Ce electron-donation than in a previously reported Dy-Fe bonded species.

We present an investigation of isostructural complexes that feature unsupported direct bonds between a formally trivalent lanthanide ion (Dy ) and either a first-row (Fe) or a second-row (Ru) transition metal (TM) ion. The sterically rigid, yet not too bulky ligand PyCp (PyCp =[2,6-(CH C H ) C H N] ) facilitates the isolation and characterization of PyCp Dy-FeCp(CO) (1; d(Dy-Fe)=2.884(2) Å) and PyCp Dy-RuCp(CO) (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.

We utilized a rigid ligand platform PyCp (PyCp = [2,6-(CHCH)CHN]) to isolate dinuclear Dy complexes [(PyCp)Dy-(μ-OSOCF)] (1) and [(PyCp)Dy-(μ-Cl)] (3) as well as the mononuclear complex (PyCp)Dy(OSOCF)(thf) (2). Compounds 1 and 2 are the first examples of organometallic Dy complexes featuring triflate binding. The isolation of compounds 1 and 3 allows us to comparatively evaluate the effects of the bridging anions on the magnetization dynamics of the dinuclear systems. Our investigations show that although the exchange coupling interactions differ for 1 and 3, the dynamic magnetic properties are dominated by relaxation via the first excited state Kramers doublet of the individual Dy sites. Compounds 1 and 3 exhibit barriers to magnetization reversal (U = 49 cm) that can be favorably compared to those of the previously reported examples of [CpDy(μ-Cl)] (U = 26 cm) and [CpDy(thf)(μ-Cl)] (U = 34 cm).