Introducing the Bis(mesitoyl)phosphide Ligand into Dinuclear Trivalent Rare Earth Metal Coordination Chemistry

Anionic ancillary ligands play a critical role in the construction of rare earth (RE) metal complexes due to the large influence on the stability of the molecule and engendering emergent electronic properties that are of interest in a plethora of applications. Supporting ligands comprising oxygen donor atoms are highly pursued in RE chemistry owing to the high oxophilicity innate to these ions. The scarcely employed bis(acyl)phosphide (BAP) ligands feature oxygen coordination sites and contain a phosphide backbone rendering it attractive for RE-coordination chemistry. Here, we integrate bis(mesitoyl)phosphide (^mesBAP) as an ancillary ligand into RE^III chemistry to generate the first dinuclear trivalent RE complexes containing BAP ligands; [{^mesBAP}₂RE(THF)(μ-Cl)]₂ (RE=Y, (1), Gd (2), and Dy (3); THF=tetrahydrofuran). Each RE center is ligated to two monoanionic ^mesBAP ligands, one THF molecule and one chloride ion. All three molecules were characterized through single-crystal X-ray diffraction, ³¹P NMR, IR and UV-Vis spectroscopy. ³¹P, ¹H and ¹³C NMR on the diamagnetic yttrium congener 1 confirm asymmetric ligand coordination. DFT calculations conducted on 2 provided insight into the electronic structure. The magnetic properties of 2 and 3 were investigated via SQUID magnetometry. The Gd^III ions exhibit weak antiferromagnetic coupling, corroborated by DFT results.