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The reaction of [AnCl(NR2)3] (An = U, Th, R = SiMe3) with in situ generated lithium-3,3-diphenylcyclopropene results in the formation of [{(NR2)3}An(CH[double bond, length as m-dash]C[double bond, length as m-dash]CPh2)] (An = U, 1; Th, 2) in good yields after work-up. Deprotonation of 1 or 2 with LDA/2.2.2-cryptand results in formation of the anionic allenylidenes, [Li(2.2.2-cryptand)][{(NR2)3}An(CCCPh2)] (An = U, 3; Th, 4). The calculated 13C NMR chemical shifts of the Cα, Cβ, and Cγ nuclei in 2 and 4 nicely reproduce the experimentally assigned order, and exhibit a characteristic spin-orbit induced downfield shift at Cα due to involvement of the 5f orbitals in the Th-C bonds. Additionally, the bonding analyses for 3 and 4 show a delocalized multi-center character of the ligand π orbitals involving the actinide. While a single-triple-single-bond resonance structure (e.g., An-C[triple bond, length as m-dash]C-CPh2) predominates, the An[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]CPh2 resonance form contributes, as well, more so for 3 than for 4.

The reaction of UCl4 or ThCl4(DME)2 (DME = dimethoxyethane) with 1,4,7,10-tetrazacyclododecane-1,4,7,10-tetraacetic acid (H4DOTA), and 6 equiv of triethylamine, in dimethyl sulfoxide (DMSO) results in the formation of [AnIV(κ8-DOTA)(DMSO)] (1, An = U; 2, An = Th), which can be isolated in moderate yields after workup. Complexes 1 and 2 are the first structurally characterized actinide-DOTA complexes to feature the κ8 binding mode for the DOTA ligand. In addition, we isolated a few crystals of [U(κ4-H2DOTA)(DMSO)4][Cl]2 (3). Crystallographic characterization of this material reveals that the [H2DOTA]2- ligand in 3 is only coordinated to U4+ by its four carboxylate arms, generating an overall κ4 binding mode. Similar complexes have been previously proposed as intermediates along the H4DOTA complexation pathway, but this intermediate had not been structurally characterized until now.

While halide double perovskites A2M(I)M(III)X6 have attracted significant attention, examples involving iodides are rare. We examine the limits of the structural stability of iodide double perovskites, presenting the synthesis and single‐crystal structures of Cs2NaScI6 and Cs2NaYI6. Bypassing the common expectation that iodides have small band gaps, these compounds display optical gaps of 3.10 eV [M(III) = Sc] and 3.65 eV [M(III) = Y]. Cs2NaScI6 is the only iodide double perovskite to exhibit a cubic crystal structure at room temperature. Density functional theory‐based electronic structure calculations help understand the role of competing Cs3M(III)2I9 (3 : 2 : 9) phases and provide possible reasons for why iodide double perovskites based around In(III), Sb(III) and Bi(III) cations have proved elusive. We confirm design rules for halide double perovskites based around concepts of the tolerance factor and the radius ratio of the smaller, trivalent ion, but also point to situations such as what is observed for Cs2NaScI6 where a double perovskite can be trapped in a metastable structure. [ABSTRACT FROM AUTHOR]

Addition of 2 equiv. of bis(diisopropylamino)cyclopropenylidene (BAC) to [U(NR2)3(CCPh)] (1, R = SiMe3), in Et2O, results in formation of [cyclo-N(iPr)C(Me)2CH(NiPr2)C{＝CHC3(NiPr2)2}][U(NR2)2(N(SiMe3)SiMe2CH2)(CCPh)] (2) in moderate isolated yield. Complex 2 is the result of coupling and protonation of two BAC molecules, where complex 1 contributes the required proton. It was characterized by NMR spectroscopy and X-ray crystallography and represents a new mode of reactivity of the cyclopropenylidene fragment. [ABSTRACT FROM AUTHOR]

Addition of 2 equiv. of bis(diisopropylamino)cyclopropenylidene (BAC) to [U(NR2)3(CCPh)] (1, R = SiMe3), in Et2O, results in formation of [cyclo-N(iPr)C(Me)2CH(NiPr2)C{＝CHC3(NiPr2)2}][U(NR2)2(N(SiMe3)SiMe2CH2)(CCPh)] (2) in moderate isolated yield. Complex 2 is the result of coupling and protonation of two BAC molecules, where complex 1 contributes the required proton. It was characterized by NMR spectroscopy and X-ray crystallography and represents a new mode of reactivity of the cyclopropenylidene fragment. [ABSTRACT FROM AUTHOR]

Addition of 2 equiv. of bis(diisopropylamino)cyclopropenylidene (BAC) to [U(NR 2 ) 3 (CCPh)] (1, R = SiMe 3 ), in Et 2 O, results in formation of [ cyclo -N( i Pr)C(Me) 2 CH(N i Pr 2 )C{CHC 3 (N i Pr 2 ) 2 }][U(NR 2 ) 2 ( N (SiMe 3 )SiMe 2 C H 2 )(CCPh)] (2) in moderate isolated yield. Complex 2 is the result of coupling and protonation of two BAC molecules, where complex 1 contributes the required proton. It was characterized by NMR spectroscopy and X-ray crystallography and represents a new mode of reactivity of the cyclopropenylidene fragment.

Halide double perovskites [A 2 M I M III X 6 ] are an important class of materials that have garnered substantial interest as non-toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs 2 NaLnI 6 (Ln=Ce, Nd, Gd, Tb, Dy). The complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported., (© 2023 Wiley-VCH GmbH.)

The reaction of [AnCl(NR 2 ) 3 ] (An = U, Th, R = SiMe 3 ) with in situ generated lithium-3,3-diphenylcyclopropene results in the formation of [{(NR 2 ) 3 }An(CH[double bond, length as m-dash]C[double bond, length as m-dash]CPh 2 )] (An = U, 1 ; Th, 2 ) in good yields after work-up. Deprotonation of 1 or 2 with LDA/2.2.2-cryptand results in formation of the anionic allenylidenes, [Li(2.2.2-cryptand)][{(NR 2 ) 3 }An(CCCPh 2 )] (An = U, 3 ; Th, 4 ). The calculated 13 C NMR chemical shifts of the C α , C β , and C γ nuclei in 2 and 4 nicely reproduce the experimentally assigned order, and exhibit a characteristic spin-orbit induced downfield shift at C α due to involvement of the 5f orbitals in the Th-C bonds. Additionally, the bonding analyses for 3 and 4 show a delocalized multi-center character of the ligand π orbitals involving the actinide. While a single-triple-single-bond resonance structure ( e.g. , An-C[triple bond, length as m-dash]C-CPh 2 ) predominates, the An[double bond, length as m-dash]C[double bond, length as m-dash]C[double bond, length as m-dash]CPh 2 resonance form contributes, as well, more so for 3 than for 4 ., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Reaction of 1 equiv of KN(SiMe 3 ) 2 with 9-fluorenone results in the formation of (Me 3 Si)N═C 13 H 8 ( 1 ) in high yield after work-up. Addition of 1 equiv of phenol to 1 results in rapid desilylation and formation of 9-fluorenone imine, HN═C 13 H 8 ( 2 ). Subsequent reaction of 2 with 1 equiv of LiN i Pr 2 results in deprotonation and formation of [Li(Et 2 O)] 4 [N═C 13 H 8 ] 4 ( 3 ) in good yield. Reaction of 1 equiv of KN(SiMe 3 ) 2 with 2-adamantanone for 7 days at room temperature results in the formation of (Me 3 Si)N═C 10 H 14 ( 4 ) in good yield. Dissolution of 4 in neat MeOH results in rapid desilylation concomitant with formation of 2-adamantanone imine, HN═C 10 H 14 ( 5 ). Subsequent reaction of 5 with 1 equiv of LiN i Pr 2 results in formation of [Li(THF)] 4 [N═C 10 H 14 ] 4 ( 6 ). Both 3 and 6 were characterized by X-ray crystallography. Finally, reaction of CrCl 3 with 3.5 equiv of 6 results in formation of the [Cr 2 ] 6+ dimer, [Li][Cr 2 (N═C 10 H 14 ) 7 ] ( 7 ), which can be isolated in modest yield after work-up. Complex 7 features a Cr-Cr bond length of 2.653(2) Å. Additionally, solid-state magnetic susceptibility measurements reveal strong antiferromagnetic coupling between the two Cr centers, with J = -200 cm -1 .

The solid-state 15 N NMR powder spectra of the thorium nitride complex, [K(18-crown-6)(THF) 2 ][(R 2 N) 3 Th(μ- 15 N)Th(NR 2 ) 3 ] ( [K][1- 15 N] , R = SiMe 3 ), and the thorium amide complex, [Th(NR 2 ) 3 ( 15 NH 2 )] ( 2- 15 N ), were recorded. The spectrum for [K][1- 15 N] represents the first reported solid-state 15 N NMR data for an actinide complex. The experimentally measured tensor spans are Ω = 847 ppm for [K][1- 15 N] and Ω = 237 ppm for 2- 15 N . Both shielding tensors exhibit axial symmetry, which for [K][1- 15 N] is consistent with a local rotational symmetry of its 15 N-labeled nitride ligand. For 2- 15 N , the axial asymmetry can be rationalized by a quasi-free Th-NH 2 bond rotation in the solid-state. Density functional theory calculations overestimate the tensor span somewhat for [K][1- 15 N] , but provide isotropic shifts in good agreement with both the solid-state and solution values for both complexes. Natural localized molecular orbital analyses of the nuclear shielding reveal that the larger tensor span in [K][1- 15 N] vs 2- 15 N is primarily a consequence of more pronounced covalency of the σ(N-Th) bonds and large spin-orbit coupling due to significant Th 5f orbital contribution to those bonds, impacting the principal components of the shielding tensor perpendicular to the Th-N-Th axis. Overall, our analysis confirms the involvement of the 5f orbitals in Th-N multiple bonds and further demonstrates the value of solid-state NMR spectroscopy for interrogating actinide-ligand bonding.