Homoleptic Uranium–Bis(acyl)phosphide Complexes

Abstract

The first uranium bis­(acyl)­phosphide (BAP) complexes were synthesized from the reaction between sodium bis­(mesitoyl)­phosphide (Na­( mes BAP)) or sodium bis­(2,4,6-triisopropylbenzoyl)­phosphide (Na­( tripp BAP)) and UI3(1,4-dioxane)1.5. Thermally stable, homoleptic BAP complexes were characterized by single-crystal X-ray diffraction and electron paramagnetic resonance (EPR) spectroscopy, when appropriate, for the elucidation of the electronic structure and bonding of these complexes. EPR spectroscopy revealed that the BAP ligands on the uranium center retain a significant amount of electron density. The EPR spectrum of the trivalent U­( tripp BAP) 3 has a rhombic signal near g = 2 (g 1 = 2.03; g 2 = 2.01; and g 3 = 1.98) that is consistent with the EPR-observed unpaired electron being located in a molecular orbital that appears ligand-derived. However, upon warming the complex to room temperature, no resonance was observed, indicating the presence of uranium character.

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

“…C 6 D 6 was purchased from Cambridge Isotope Laboratories. Na mes BAP − and Na tripp BAP were synthesized from previously reported procedures. EuCl 3 and EuI 2 were purchased in ampoules from commercial sources (Strem and Sigma-Aldrich, respectively) and used as received.…”

“…We recently investigated the uranium coordination chemistry with two different BAP ligands: sodium bis­(mesitoyl)­phosphide ( Na­( mes BAP) ) and sodium bis­(2,4,6-triisopropylbenzoyl)­phosphide ( Na­( tripp BAP) ). − Installation of the smaller mes BAP – analogue on a uranium center afforded the homoleptic complex U­( mes BAP) 4 , arising from ligand redistributions and single electron chemistry. − The phosphorus atom in the backbone of the BAP ligands was found to be a good spectroscopic probe of these complexes via the utility of 31 P NMR spectroscopy. To generate the trivalent U-complex, the larger BAP ligand, Na­( tripp BAP) , was required to prevent undesired rearrangements and furnish the desired U­(BAP) 3 complex.…”

“…The electronic structure of U­( tripp BAP) 3 is complex, with the uranium center being best described as existing on a continuum between U 4+ and U 3+ . Here, the tripp BAP – ligand framework accommodates a significant amount of electron density at low temperatures as determined by EPR spectroscopic studies (EPR = electron paramagnetic resonance) …”

“…Here, the tripp BAP − ligand framework accommodates a significant amount of electron density at low temperatures as determined by EPR spectroscopic studies (EPR = electron paramagnetic resonance). 38 The observed differences in reactivity between mes BAP − and tripp BAP − ligands toward uranium, combined with the spectroscopic benefits of BAP over Acac, encouraged us to further investigate the coordination chemistry of the BAP − motif in f-element chemistry. Herein, we describe the synthesis and characterization of a series of BAP − -supported Eu complexes, Eu( mes BAP) 3 (thf) 2 , Eu( tripp BAP) 3 , and Eu-( tripp BAP) 2 (dme) 2 (thf = tetrahydrofuran, dme = 1,2dimethoxyethane), with this report specifically investigating the resultant magnetic properties of the Eu 3+ and Eu 2+ complexes (Scheme 1).…”

Bis(acyl)phosphide ‐ Ambidentate Ligands for the Synthesis of Group 14 and 15 Main Group Element Compounds

“…A similar situation is encountered in β‐diketones, the anions of which are versatile ligands, for example acetylacetonate, acac − [6] . Analogously, several transition, main group metal, yttrium and uranium complexes incorporating the BAP − ligand have been synthesized (Scheme 1b) [4,7–9] . Generally, the coordination occurs in the chelating κ 2 ‐O,O′ mode.…”