Magnetism Studies of Bis(acyl)phosphide-Supported Eu³⁺and Eu²⁺Complexes

Abstract

A series of bis(acyl)phosphide-supported Eu complexes were synthesized (bis(acyl)phosphide = BAP). In this study, BAP ligands proved to be excellent ligands for the synthesis of both Eu3+ and Eu2+ molecular complexes. Sodium bis(mesitoyl)phosphide (Na( mes BAP)) and sodium bis(2,4,6-triisopropylbenzoyl)phosphide (Na( tripp BAP)) were employed as ligand precursors for the synthesis of the Eu3+ complexes Eu(bis(mesitoyl)phosphide)3(thf)2 (Eu( mes BAP) 3 (thf) 2 ) and Eu(bis(2,4,6-triisopropylbenzoyl)phosphide)3 (Eu( tripp BAP) 3 ), as well as the Eu2+ complex, Eu(bis(2,4,6-triisopropylbenzoyl)phosphide)2(dme)2 (Eu( tripp BAP) 2 (dme) 2 ) (thf = tetrahydrofuran, dme = 1,2-dimethoxyethane). All complexes were characterized using a combination of UV–vis–NIR–IR and NMR spectroscopies, and single-crystal X-ray diffraction (SC-XRD). The magnetic properties of these three monomeric Eu complexes were investigated by variable-temperature magnetic susceptibility. The magnetic data are typical for these ions, with Eu( tripp BAP) 2 (dme) 2 displaying Curie-type behavior. Both Eu( tripp BAP) 3 and Eu( mes BAP) 3 (thf) 2 possess similar 7F0-7F1 spin–orbit energy gaps and a similar zero-field splitting of the 7F1 state.

Determining the Effects of Zero-Field Splitting and Magnetic Exchange in Dimeric Europium(II) Complexes

“…The 1 H NMR spectrum of [Eu­( mes BAP) 2 (et 2 o)] 2 comprises broadened resonances consistent with a highly paramagnetic complex, with no observable resonances outside the 0–4 ppm range. No resonances were observed in the 31 P­{ 1 H} NMR spectrum over an 800-ppm range using freshly prepared [Eu­( mes BAP) 2 (et 2 o)] 2 , which is consistent with a previously reported Eu 2+ -BAP compound . After Eu 2+ -BAP is allowed to stand, a broad (330 Hz) resonance centered at 97.6 ppm is observed, likely arising from decomposition or single-electron oxidation (Figure S2).…”

“…25−28 Monomeric Eu 3+ complexes were isolated through the treatment of EuCl 3 with sodium bis(mesitoyl)phosphide [Na( mes BAP)] or sodium bis(2,4,6-triisopropylbenzoyl)phosphide [Na-( tripp BAP)]. 26 While the use of the sterically demanding Na( tripp BAP) with EuI 2 enabled the preparation of a monomeric Eu 2+ complex, we proposed that employing the smaller steric profile Na( mes BAP) ligand in a similar reaction would instead produce the desired bimetallic Eu 2+ complex. This report describes the synthesis and characterization of two bimetallic Eu 2+ complexes, [Eu( mes BAP) 2 (et 2 o)] 2 (et 2 o = metal-bound diethyl ether) and the carbon-based analogue [Eu( mes Acac) 2 (et 2 o)] 2 ( mes Acac = 1,3-dimesityl-1,3-diketonate), and rationalizes the magnetic exchange interaction observed between the two Eu 2+ centers.…”

“…No resonances were observed in the 31 P{ 1 H} NMR spectrum over an 800-ppm range using freshly prepared [Eu-( mes BAP) 2 (et 2 o)] 2 , which is consistent with a previously reported Eu 2+ -BAP compound. 26 After Eu 2+ -BAP is allowed to stand, a broad (330 Hz) resonance centered at 97.6 ppm is observed, likely arising from decomposition or single-electron oxidation (Figure S2). [Eu( mes Acac) 2 (et 2 o)] 2 displays a broad (>500 Hz) resonance centered at ∼2.4 ppm in the 1 H NMR spectrum.…”

“…Prior work demonstrated the value of employing bis­(acyl)­phosphide (BAP) ligands in the generation of actinide and lanthanide complexes of varied oxidation states. − Monomeric Eu 3+ complexes were isolated through the treatment of EuCl 3 with sodium bis­(mesitoyl)­phosphide [Na­( mes BAP)] or sodium bis­(2,4,6-triisopropylbenzoyl)­phosphide [Na­( tripp BAP)] . While the use of the sterically demanding Na­( tripp BAP) with EuI 2 enabled the preparation of a monomeric Eu 2+ complex, we proposed that employing the smaller steric profile Na­( mes BAP) ligand in a similar reaction would instead produce the desired bimetallic Eu 2+ complex.…”

A Genuine Trivalent Bis‐Acylphosphide (BAP) Complex of Uranium

“…Only recently, the first f ‐element complexes in the form of the homoleptic BAP uranium complexes [U( tripp BAP) 3 ] and [U IV ( mes (BAP) 4 ] were reported by Tondreau et al ., where tripp BAP=bis(2,4,6‐trisisopropylbenzoyl)phosphide and mes BAP=bis(2,4,6‐ trimethylbenzoyl)phosphide were used as ligands (see Figure 1). [6] Following this study, the europium complexes in the form of [Eu( tripp BAP) 3 ], [Eu( tripp BAP) 2 (dme) 2 ] and [Eu( mes BAP) 3 (thf) 2 ] were published shortly after [2b] …”