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We examine lanthanide (Ln)-ligand bonding in a family of early Ln 3+ complexes [Ln(Cp tt ) 3 ] (1-Ln, Ln = La, Ce, Nd, Sm; Cp tt = C 5 H 3 t Bu 2 -1,3) by pulsed electron paramagnetic resonance (EPR) methods, and provide the first characterization of 1-La and 1-Nd by single crystal XRD, multinuclear NMR, IR and UV/Vis/NIR spectroscopy. We measure electron spin T 1 and T m relaxation times of 12 and 0.2 μs (1-Nd), 89 and 1 μs (1-Ce) and 150 and 1.7 μs (1-Sm), respectively, at 5 K: the T 1 relaxation of 1-Nd is more than 10 2 times faster than its valence isoelectronic uranium analogue. 13 C and 1 H hyperfine sublevel correlation (HYSCORE) spectroscopy reveals that the extent of covalency is negligible in these Ln compounds, with much smaller hyperfine interactions than observed for equivalent actinide (Th and U) complexes. This is corroborated by ab initio calculations, confirming the predominant electrostatic nature of the metal-ligand bonding in these complexes., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

The coordination and organometallic chemistry of the f-elements, that is group 3, lanthanide, and actinide ions, supported by nitrogen ligands, e.g. amides, imides, and nitrides, has become well developed over many decades. In contrast, the corresponding f-element chemisty with the heavier pnictogen analogues phosphorus, arsenic, antimony, and bismuth has remained significantly underdeveloped, due largely to a lack of suitable synthetic methodologies and also the inherent hard(f-element)-soft(heavier pnictogen) acid-base mismatch, but has begun to flourish in recent years. Here, we review complexes containing chemical bonds between the f-elements and heavy pnictogens from phosphorus to bismuth that spans five decades of endeavour. We focus on complexes whose identity has been unambiguously established by structural authentication by single-crystal X-ray diffraction with respect to their synthesis, characterisation, bonding, and reactivity, in order to provide a representative overview of this burgeoning area. By highlighting that much has been achieved but that there is still much to do this review aims to inspire, focus and guide future efforts in this area., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Respiratory virus infections cause significant morbidity and mortality ranging from mild uncomplicated acute respiratory illness to severe complications, such as acute respiratory distress syndrome, multiple organ failure, and death during epidemics and pandemics. We present a protocol to systematically study patients with severe acute respiratory infection (SARI), including severe acute respiratory syndrome coronavirus 2, due to respiratory viral pathogens to evaluate the natural history, prognostic biomarkers, and characteristics, including hospital stress, associated with clinical outcomes and severity., Design: Prospective cohort study., Setting: Multicenter cohort of patients admitted to an acute care ward or ICU from at least 15 hospitals representing diverse geographic regions across the United States., Patients: Patients with SARI caused by infection with respiratory viruses that can cause outbreaks, epidemics, and pandemics., Interventions: None., Measurements and Main Results: Measurements include patient demographics, signs, symptoms, and medications; microbiology, imaging, and associated tests; mechanical ventilation, hospital procedures, and other interventions; and clinical outcomes and hospital stress, with specimens collected on days 0, 3, and 7-14 after enrollment and at discharge. The primary outcome measure is the number of consecutive days alive and free of mechanical ventilation (VFD) in the first 30 days after hospital admission. Important secondary outcomes include organ failure-free days before acute kidney injury, shock, hepatic failure, disseminated intravascular coagulation, 28-day mortality, adaptive immunity, as well as immunologic and microbiologic outcomes., Conclusions: SARI-Preparedness is a multicenter study under the collaboration of the Society of Critical Care Medicine Discovery, Resilience Intelligence Network, and National Emerging Special Pathogen Training and Education Center, which seeks to improve understanding of prognostic factors associated with worse outcomes and increased resource utilization. This can lead to interventions to mitigate the clinical impact of respiratory virus infections associated with SARI., Competing Interests: Dr. Anesi receives research funding from the Agency for Healthcare Research and Quality and reports payments for authoring COVID-19 chapters for UpToDate and for expert witness consulting. Dr. Segal receives grant funding from the National Institutes of Health (Method to Extend Research in Time R37 CA244775) paid to institution, and Dr. Wyles receives funding from Gilead Sciences paid to institution (ended August 31, 2021). The remaining authors have disclosed that they do not have any potential conflicts of interest.

The reaction of [UO 2 (μ-Cl) 4 {K(18-crown-6)} 2 ] with [{N(CH 2 CH 2 NSiPr i 3 ) 3 }Li 3 ] gives [{UO(μ-NCH 2 CH 2 N[CH 2 CH 2 NSiPr i 3 ] 2 )} 2 ] ( 1 ), [{(LiCl)(KCl)(18-crown-6)} 2 ] ( 2 ), and [LiOSiPr i 3 ] ( 3 ) in a 1:2:2 ratio. The formation of the oxo-imido 1 involves the cleavage of a N-Si bond and the activation of one of the usually robust U═O bonds of uranyl(VI), resulting in the formation of uranium(VI)-imido and siloxide linkages. Notably, the uranium oxidation state remains unchanged at +6 in the starting material and product. Structural characterization suggests the dominance of a core RN═U═O group, and the dimeric formulation of 1 is supported by bridging imido linkages in a highly asymmetric U 2 N 2 ring. Density functional theory analyses find a σ > π orbital energy ordering for the U═N and U═O bonds in 1 , which is uranyl-like in nature. Complexes 1 - 3 were characterized variously by single crystal X-ray diffraction, multinuclear NMR, IR, Raman, and optical spectroscopies; cyclic voltammetry; and density functional theory.

Organometallic lanthanide (Ln) chemistry is dominated by complexes that contain substituted cyclopentadienyl (CpR) ligands. Closely related phospholyls have received less attention, and although they have proven utility in stabilising low oxidation state Ln complexes the trivalent Ln chemistry of these ligands is limited in comparison. Herein, we synthesise two families of heteroleptic Ln3+ complexes, [Ln(Htp)2(μ-BH4)]2 (Htp = 2,5-di-tert-butylphospholyl; 1-Ln; Ln = La, Ce, Nd, Sm), and [[Ln(Htp)2(μ-BH4)2K(S)]n (2-Ln, Ln = La, Ce, S = 2 DME, n = 2; 3-Ce, Ln = Ce, S = Et2O and THF, n = ∞) via the reactions of parent [Ln(BH4)3(THF)3.5] with K(Htp), to investigate differences between Ln complexes with substituted phospholyl ligands and analogous CpR complexes. Complexes 1-3-Ln were characterised as appropriate by single crystal XRD, SQUID magnetometry, elemental analysis, multinuclear NMR, ATR-IR and UV-Vis-NIR spectroscopy. Ab initio calculations reveal that small changes in the Ln3+ coordination spheres of these complexes can have relatively large influences on crystal field splitting.

A fundamental bonding model in coordination and organometallic chemistry is the synergic, donor-acceptor interaction between a metal and a neutral π-acceptor ligand, in which the ligand σ donates to the metal, which π back-bonds to the ligand. This interaction typically involves a metal with an electron-rich, mid-, low- or even negative oxidation state and a ligand with a π* orbital. Here, we report that treatment of a uranium-carbene complex with an organoazide produces a uranium(V)-bis(imido)-dinitrogen complex, stabilized by a lithium counterion. This complex, which was isolated in a crystalline form, involves an electron-poor, high-oxidation-state uranium(V) 5f 1 ion that is π back-bonded to the poor π-acceptor ligand dinitrogen. We propose that this is made possible by a combination of cooperative heterobimetallic uranium-lithium effects and the presence of suitable ancillary ligands that render the uranium ion unusually electron rich. This electron-poor back-bonding could have implications for the field of dinitrogen activation.

We report the preparation of a range of alkali metal uranyl(VI) tri- bis(silyl)amide complexes [{M(THF) x }{(μ-O)U(O)(N″) 3 }] (1M) (N″ = {N(SiMe 3 ) 2 } - , M = Li, Na, x = 2; M = K, x = 3; M = K, Rb, Cs, x = 0) containing electrostatic alkali metal uranyl-oxo interactions. Reaction of 1M with 2,2,2-cryptand or 2 equiv of the appropriate crown ether resulted in the isolation of the separated ion pair species [U(O) 2 (N″) 3 ][M(2,2,2-cryptand)] (3M, M = Li-Cs) and [U(O) 2 (N″) 3 ][M(crown) 2 ] (4M, M = Li, crown = 12-crown-4 ether; M = Na-Cs, crown = 15-crown-5 ether). A combination of crystallographic studies and IR, Raman and UV-vis spectroscopies has revealed that the 1M series adopts contact ion pair motifs in the solid state where the alkali metal caps one of the uranyl-oxo groups. Upon dissolution in THF solution, this contact is lost, and instead, separated ion pair motifs are observed, which is confirmed by the isolation of [U(O) 2 (N″) 3 ][M(THF) n ] (2M) (M = Li, n = 4; M = Na, K, n = 6). The compounds have been characterized by single crystal X-ray diffraction, multinuclear NMR spectroscopy, IR, Raman, and UV-vis spectroscopies, and elemental analyses.

Reaction of [U{C(SiMe 3 )(PPh 2 )}(BIPM)(μ-Cl)Li(TMEDA)(μ-TMEDA) 0.5 ] 2 (BIPM=C(PPh 2 NSiMe 3 ) 2 ; TMEDA=Me 2 NCH 2 CH 2 NMe 2 ) with [Rh(μ-Cl)(COD)] 2 (COD=cyclooctadiene) affords the heterotrimetallic U IV -Rh I 2 complex [U(Cl) 2 {C(PPh 2 NSiMe 3 )(PPh[C 6 H 4 ]NSiMe 3 )}{Rh(COD)}{Rh(CH(SiMe 3 )(PPh 2 )}]. This complex has a very short uranium-rhodium distance, the shortest uranium-rhodium bond on record and the shortest actinide-transition metal bond in terms of formal shortness ratio. Quantum-chemical calculations reveal a remarkable RhI→→ U IV net double dative bond interaction, involving Rh I 4dz2 - and 4d xy/xz -type donation into vacant U IV 5f orbitals, resulting in a Wiberg/Nalewajski-Mrozek U-Rh bond order of 1.30/1.44, respectively. Despite being, formally, purely dative, the uranium-rhodium bonding interaction is the most substantial actinide-metal multiple bond yet prepared under conventional experimental conditions, as confirmed by structural, magnetic, and computational analyses., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)