A Very Short Uranium(IV)–Rhodium(I) Bond with Net Double‐Dative Bonding Character

Abstract

Reaction of [U{C(SiMe 3 )(PPh 2 )}(BIPM)(m-Cl)Li-(TMEDA)(m-TMEDA) 0.5 ] 2 (BIPM=C(PPh 2 NSiMe 3 ) 2 ; TMEDA = Me 2 NCH 2 CH 2 NMe 2 )w ith [Rh(m-Cl)(COD)] 2 (COD = cyclooctadiene) affords the heterotrimetallic U IV À.This complex has avery short uranium-rhodium distance,t he shortest uranium-rhodium bond on recordand the shortest actinide-transition metal bond in terms of formal shortness ratio.Q uantum-chemical calculations reveal ar emarkable Rh I! ! U IV net double dative bond interaction, involving Rh I 4d z 2 -and 4d xy/xz -type donation into vacant U IV 5f orbitals,r esulting in aW iberg/Nalewajski-Mrozek U À Rh bond order of 1.30/1.44, respectively.D espite being,f ormally,p urely dative,t he uranium-rhodium bonding interaction is the most substantial actinide-metal multiple bond yet prepared under conventional experimental conditions,a s confirmed by structural, magnetic,a nd computational analyses.

Identification of a uranium–rhodium triple bond in a heterometallic cluster

“…Uranium, yellow; rhodium, green; phosphorus, violet red; nitrogen, blue; chlorine, yellow-green; carbon, gray. (26,(36)(37)(38)(39), and is consistent with the short uranium-rhodium triple bond. The similar magnetic behaviors of 2 and 3 are however in agreement with the assignment of a uranium(IV) oxidation state.…”

“…This is the highest number of U-Rh bonds observed in a molecule. (26). The U1-Rh1 and U2-Rh3 bond lengths are even shorter than the sum of the covalent double-bond radii of uranium and rhodium (2.44 Å) and only 0.07 Å (3%) longer than the sum of the covalent triple-bond radii of uranium and rhodium (2.24 Å) (31,32).…”

“…Interestingly, such a molecule was reported recently by Knecht et al and shown by state-of-the-art relativistic quantumchemical calculations to contain a quadruple bond (24). Two recent landmark experimental advances in this field are the generation of a U-Fe triple bond in the gas phase under laser vaporization by Zhou and coworkers (25) and the synthesis of a double-dative bond between Rh and U by Liddle and coworkers (26).…”

[UF6]2−: A Molecular Hexafluorido Actinide(IV) Complex with Compensating Spin and Orbital Magnetic Moments

“…[4] Recent spectroscopic and theoretical investigations have aimed at ad etailed understanding of the electronic structure of actinide ions,w hich is significantly more complicated than for lanthanides. [5] The large spin-orbit coupling of actinide ions and the less shielded nature of their 5f orbitals relative to the 4f orbitals,result in much stronger interactions of the fe lectrons with the surrounding atoms.H ence,t he concomitant stronger ligand field cannot be considered as ap erturbation, particularly for the early members of the 5f series.F urthermore,s pectroscopic data of actinide systems are typically very rich and the determination of the electronic energy level-splitting and -composition remains quite challenging.F or the magnetic characterization of actinide-based materials,p owder and thermodynamically averaged magnetization data bring only limited information about the underlying physics.H owever, since the magnetic properties are predominantly defined by the energy levels that are thermally populated at room temperature and below,a ny additional experimental information on these low-lying energy levels would be of great relevance.F or this task, X-ray magnetic circular dichroism spectroscopy is ap owerful tool able to deconvolute the macroscopically measured magnetic moment into its spin and orbital contributions. [6] Despite its routine applications in magnetism, this technique has never been applied to molecular actinide systems.…”

Rücktitelbild: [UF6]2−: A Molecular Hexafluorido Actinide(IV) Complex with Compensating Spin and Orbital Magnetic Moments (Angew. Chem. 44/2019)

“…[3] Such complexes are also interesting building blocks for magnetic polynuclear complexes and one-dimensional coordination polymers. [5] The large spin-orbit coupling of actinide ions and the less shielded nature of their 5f orbitals relative to the 4f orbitals,result in much stronger interactions of the fe lectrons with the surrounding atoms.H ence,t he concomitant stronger ligand field cannot be considered as ap erturbation, particularly for the early members of the 5f series.F urthermore,s pectroscopic data of actinide systems are typically very rich and the determination of the electronic energy level-splitting and -composition remains quite challenging.F or the magnetic characterization of actinide-based materials,p owder and thermodynamically averaged magnetization data bring only limited information about the underlying physics.H owever, since the magnetic properties are predominantly defined by the energy levels that are thermally populated at room temperature and below,a ny additional experimental information on these low-lying energy levels would be of great relevance.F or this task, X-ray magnetic circular dichroism spectroscopy is ap owerful tool able to deconvolute the macroscopically measured magnetic moment into its spin and orbital contributions. [5] The large spin-orbit coupling of actinide ions and the less shielded nature of their 5f orbitals relative to the 4f orbitals,result in much stronger interactions of the fe lectrons with the surrounding atoms.H ence,t he concomitant stronger ligand field cannot be considered as ap erturbation, particularly for the early members of the 5f series.F urthermore,s pectroscopic data of actinide systems are typically very rich and the determination of the electronic energy level-splitting and -composition remains quite challenging.F or the magnetic characterization of actinide-based materials,p owder and thermodynamically averaged magnetization data bring only limited information about the underlying physics.H owever, since the magnetic properties are predominantly defined by the energy levels that are thermally populated at room temperature and below,a ny additional experimental information on these low-lying energy levels would be of great relevance.F or this task, X-ray magnetic circular dichroism spectroscopy is ap owerful tool able to deconvolute the macroscopically measured magnetic moment into its spin and orbital contributions.…”