Synthesis and Characterization of Phosphanophenolate-Based Rare-Earth Metal-Copper Complexes

The reaction of [Ln^III(OAr^P-κ²O,P)₃] (1-Ln, Ln = La, Sm, Y, Yb, and Ar^PO^- = 2,4-^tBu₂-6-(Ph₂P)C₆H₂O^-) with the copper(I) triflate toluene adduct yields the corresponding dinuclear rare-earth metal(III)-copper(I) complexes [Ln^III(OTf)(μ-OAr^P-1κ¹O,2κ¹P)₃Cu^I] (2-Ln, Ln = La, Sm, Y, Yb) in clean conversion. In order to explore an alternative synthetic route by starting from a mononuclear copper complex instead of a rare-earth metal complex, the mononuclear copper complex [(HOAr^P-κP)₃Cu^IOTf] (3) was prepared from copper(I) triflate toluene adduct and HOAr^P. However, the reaction of 3 with [Ln^III[N(SiMe₃)₂]₃] (Ln = La, Y) gave the heterobimetallic complexes only in low yields, along with undesired side-products. Investigation into the exchange of the triflate in 2-Ln for different groups was explored using alkaline metal amides, alkyls, and alkoxides and was successful only for reactions with KO^tBu, yielding [Ln^III(O^tBu)(μ-OAr^P-1κ¹O,2κ¹P)₃Cu^I] (4-Ln, Ln = La, Sm, Y, Yb). The compounds were characterized by NMR, UV-vis, and IR spectroscopy, single-crystal X-ray diffraction, and elemental analysis. The effective magnetic moments of the paramagnetic complexes were determined via the Evans NMR method.