Treatment of the thorium dimethyl metallocene (η5-C5Me5)2ThMe2 (1) with dippNH2 (dipp = 2,6-iPr2C6H3) in toluene in the presence of 4-dimethylaminopyridine (dmap) affords the terminal thorium imido metallocene (η5-C5Me5)2Th(═Ndipp)(dmap) (4), accompanied by methane releases. Complex 4 shows broad reactivity in small molecule activation. For example, 4 may activate S8, alkynes, carbodiimides, aldehydes, CS2, organic nitriles and isonitriles, and organic azides, yielding metallaheterocycle, pyridyl amido, oxido, and bis-amido complexes, respectively. Moreover, while 4 forms with Me3PO the adduct (η5-C5Me5)2Th(═Ndipp)(OPMe3) (5), the imido moiety may promote deprotonation reactions as established by its reactions with thiazole, pyridine-N-oxide derivative 2-MepyNO, amine mesitylNH2, hydrazine derivative PhNHNHPh, terminal alkyne PhC≡CH, cyclohexanone, amidate PhCONHPh, imine Ph2C═NH, and nitriles PhCH2CN and C6H11CN. In addition, the imido moiety may also behave as a nucleophile toward PhSiH2Cl, whereas 4 undergoes a Friedel-Crafts type reaction with Me3SiX (X = Cl, I, N3) and Ph3CN3. Lastly, 4 furnishes the bromo amido complex (η5-C5Me5)2Th(Br)[NH(2,6-iPr2-4-(Me5C5)C6H2)] (13) in the presence of CuBr, while the C-C coupling product [(η5-C5Me5)2Th(I)]2[μ-4,4'-(NH-2,6-iPr2C6H2)2] (14) is isolated in the presence of AgI. Furthermore, a comparison with related terminal imido thorium metallocene derivatives demonstrates nicely how different substituents on the cyclopentadienyl and imido ligands influence the reactivity of these compounds.

Treatment of (η5-C5Me5)2ThMe2 (1) with p-tolylNH2 in toluene, in the presence of 4-dimethylaminopyridine (dmap), affords a Lewis base-supported terminal thorium imido metallocene, (η5-C5Me5)2Th═N(p-tolyl)(dmap)2 (5), alongside the release of methane. In toluene solution, an equilibrium is established among complex 5, dmap, and the amido pyridyl complex (η5-C5Me5)2Th[NH(p-tolyl)][κ2-C,N-4-(Me2N)C5H3N] (5'), setting the stage for diverse reactivity. Complex 5 may initiate [2 + 2], [2 + 4], [2 + 1], or [2 + 3] cycloadditions with elemental sulfur and selenium, alkynes, carbodiimides, ketones, thio-ketones, isothiocyanates, CS2, organic nitriles and isonitriles, as well as organic azides. Moreover, imido moiety can act as a nucleophile toward metal halides, esters, and azidosilanes; and it may promote deprotonation reactions with 1-methylimidazole, 2,6-Me2C5H3NO, Me3PO, silanes, amidate PhCONH(p-tolyl), and nitriles (PhCH2CN and Ph2CHCN). Notably, reaction of 5 with Me3SiCHN2 forms the bimetallic complex [(η5-C5Me5)2Th]2(μ-N═NN═CSiMe3)2 (44) with toluene elimination. In contrast, complex 5' undergoes reactions with elemental selenium and tellurium, PhSiH2Cl, organic isonitriles (2,6-Me2C6H3NC, Me3CNC, and C6H11NC), and organic azides (p-tolylN3 and Ph3CN3) to afford amido selenido, amido tellurido, chloro pyridyl, amido pyridyl, amido alkenyl, and bis-amido complexes, respectively. Furthermore, a comparison with related terminal imido thorium metallocenes illustrates how substituent effects on the cyclopentadienyl and imido ligands influence the reactivity of these molecules.

The low-temperature reverse water-gas shift (LT-RWGS) is a critical and energy effective technology for syngas production and the mitigation of anthropogenic carbon emissions. Developing efficient and well-defined catalysts for the LT-RWGS, from which structure-activity relationships can be drawn, is a significant challenge. Herein we describe how the identification of the grafting properties of tetramesityldiiron (Fe2Mes4) helps with designing tailored and highly efficient catalysts of PtFe@SiO2 composition. To that end, a molecular analogue, Fe2Mes3OSi(OtBu)3, was synthesized and characterized by X-ray diffraction, 57Fe-Mössbauer and 1H-NMR spectroscopy. The results confirmed that tetramesityldiiron grafts onto silica via selective displacement of a single mesityl ligand, forming Fe2Mes3@SiO2, while steric hindrance likely prevents secondary interactions with surface siloxide bridges. This work highlights the potential of tetramesityldiiron as a versatile precursor for synthesizing bimetallic MFe@SiO2 systems, enabling the rational development of highly efficient LT-RWGS and CO2 hydrogenation catalysts.

Addition of dippNH2 (dipp = 2,6-iPr2Ph) to a toluene solution of thorium dimethyl metallocene (Cp2tBu)2ThMe2 (1; Cp2tBu = η5-1,3-(Me3C)2C5H3) in the presence of 4-dimethylaminopyridine (dmap) affords the Lewis base supported terminal thorium imido metallocene, (Cp2tBu)2Th(═Ndipp)(dmap) (3), concomitant with methane release. Complex 3 acts as a synthon for the (Cp2tBu)2Th(II) fragment when exposed to Ph2E2 (E = S, Se). Moreover, it activates conjugated alkynes, ketones, thio-ketones, CS2, isothiocyanates, seleno-ketones, esters, diazabutadienes, carbodiimides, organic azides, and chlorosilanes, resulting in pyridyl alkenyl complexes, dimeric oxido, sulfido, and selenido complexes, alkoxido amidate, (hetero)metallacycle, bis-amido, and dichloride complexes, respectively. Furthermore, it engages in deprotonation reactions with thiazole, terminal alkyne, ketones, amidate, imine, nitriles, and isonitriles, forming the amido thiazolyl complex, bis-alkynyl complexes, amido enolyl complexes, bis-amidates, amido-iminato complexes, amido pyridyl complexes, iminato complexes, and bis-amido complexes, respectively. In addition, it undergoes a Cannizarro-type reaction with aromatic aldehydes or Friedel-Crafts alkylation with Ph3CN3, respectively. Lastly, it forms a heterobimetallic complex (Cp2tBu)2Th(Cl)[N(dipp)Cu(dmap)] (34) in the presence of CuCl. Furthermore, substituent effects on the cyclopentadienyl and imido ligands that modulate the reactivity have been further probed.

[{Cp'Fe(μ-I)}2] (I; Cp' = η5-1,2,4-(Me3C)3C5H2) reacts with [Na(OCP)(1,4-dioxane)x] and K(OCAs) to yield [(Cp'Fe)2(μ-η2:η2-P2)(μ-CO)] (1) and [(Cp'Fe)2(μ-η2:η2-As2)(μ-CO)] (3), respectively. While complex 1 was previously accessed by Scherer and co-workers using rather harsh reaction conditions, the new synthetic method already proceeds at ambient temperature. UV-light irradiation of 1 and 3 induces CO release forming complexes [(Cp'Fe)2(μ-η2:η2-E2)] (E = P (2) and As (4)), respectively. However, both reactions also yielded several byproducts which were spectroscopically identified. Furthermore, upon thermally triggered CO elimination from 3 the Fe3As6-cluster [(Cp'Fe)3(As3)2] (5) is isolated in low yield. In addition, zero-field 57Fe Mössbauer spectra were recorded on complexes 1-4 and computational studies complement the experimental findings and provide additional insights into the bonding in these complexes and the reaction pathways resulting in the formation of complexes 1-4.

The reduction of the iron(II) half-sandwich precursors [Cp'FeN(R)(SiMe3)] (R = SiMe3, 2,6-di-iso-propylphenyl (dipp)) with KC8 yields the one-dimensional polymeric iron(I) complexes {[Cp'Fe(N(SiMe3)3)]K}n (4) and {[Cp'Fe(N(dipp)(SiMe3))]K}n (5). Addition of 18-crown-6 breaks up these chains and affords the monomeric salts [Cp'Fe(N(SiMe3)2)][K(18-crown-6)(thf)2] (6) and [Cp'Fe(N(dipp)(SiMe3))][K(18-crown-6)(thf)2] (7). All four compounds were structurally characterized by single-crystal X-ray diffraction analysis and adopt an S = 3/2 spin ground state. Zero-field 57Fe Mössbauer spectra uncover slow magnetic relaxation at low temperatures in each complex. Complementary CASSCF/NEVPT2 calculations reveal an S = 3/2 ground-state Kramers doublet that is ca. 100 cm-1 below the first excited state. These findings are confirmed by results from DC susceptibility and magnetization experiments. The slow relaxation of magnetization is further characterized via AC susceptibility measurements, unveiling detectable slow relaxation of magnetization at zero external field for 4-6. Complex 4 exhibits an unusual field dependence of the quantum tunneling of magnetization, akin to exchange-bias effects, which are commonly observed in lanthanide dimers.

The reactivity of the thorium bipyridyl metallocene (Cp-2tBu)(2)Th(bipy) (1; Cp-2tBu = eta(5)-1,3-(Me3C)(2)C5H3) toward a series of small molecules was explored, and the emerging reactivity pattern can be categorized: (1) It may act as a synthon for (Cp-2tBu)(2)Th(II) in contact with alkynes, diazabutadienes, ketazine (Ph2C & boxH;N)(2), o-benzoquinone, carbodiimides, organic azides, isothiocyanates, elemental sulfur (S-8) and selenium (Se), and Ph2S2. (2) It participates in C-C coupling reactions with ketones Ph2CO, (CH2)(5)CO, and 1-indanone, aldehydes p-MePhCHO and p-ClPhCHO, amidate PhCONH(p-tolyl), seleno-ketone (p-MeOPh)(2)CSe, imines PhCH & boxH;NPh and (p-tolyl)(2)C & boxH;NH, ketazine (PhCH & boxH;N)(2), and nitriles PhCN, Me3CCN, C6H11CN and CH3CN, to form (Cp-2tBu)(2)Th[(bipy)(Ph2CO)] (15), (Cp-2tBu)(2)Th[(bipy)((CH2)(5)CO)] (16), (Cp-2tBu)(2)Th[(bipy)(1-(C8H8)CO)] (17), (Cp-2tBu)(2)Th[(bipy)(p-MePhCHO)] (18), (Cp-2tBu)(2)Th[(bipy)(p-ClPhCHO)] (19), (Cp-2tBu)(2)Th[(bipy){PhCONH(p-tolyl)}] (20), (Cp-2tBu)(2)Th[(bipy){(p-MeOPh)(2)CSe}] (21), (Cp-2tBu)(2)Th[(bipy)(PhCHNPh)] (22), (Cp-2tBu)(2)Th[(bipy){(p-tolyl)(2)CNH}] (23), (Cp-2tBu)(2)Th[(bipy)(PhCHNN & boxH;CHPh)] (24), (Cp-2tBu)(2)Th[(bipy)(PhCN)] (25), (Cp-2tBu)(2)Th[(bipy)(Me3CCN)] (26), (Cp-2tBu)(2)Th[(bipy)(C6H11CN)] (27), and (Cp-2tBu)(2)Th[(bipy)(CH3CN)] (28), respectively. However, in the presence of benzyl nitrile PhCH2CN, the dimeric bis-amido complex {(Cp-2tBu)(2)Th[NHC(CH2Ph)C(Ph)C(C(Ph)CN)NH]}(2) (29) is isolated. (3) Isonitriles such as Me3CNC, Me3SiNC, and C6H11NC undergo C-N bond cleavage and C-C coupling to furnish the thorium isocyanido amido complexes (Cp-2tBu)(2)Th[4-(Me3C)bipy](NC) (30), (Cp-2tBu)(2)Th[4-(Me3Si)bipy](NC) (31), and (Cp-2tBu)(2)Th[4-(C6H11)bipy](NC) (32), respectively. A comparison with related thorium bipyridyl metallocene derivatives shows that minor alternations in the supporting cyclopentadienyl ligands modulate the reactivity of these compounds.

Addition of p-tolylN3 to a toluene solution of thorium bipyridyl metallocene [{eta 5-1,2,4-(Me3Si)3C5H2}2Th(bipy)] (1) causes N2 evolution concomitant with the formation of Lewis-base-supported terminal thorium imido metallocene [{eta 5-1,2,4-(Me3Si)3C5H2}2Th=N(p-tolyl)(bipy)] (2). Complex 2 may initiate [2 + 2] or [2 + 1] cycloaddition reactions with internal alkynes PhC=CPh and PhC=CC=CPh, thiobenzophenone Ph2CS, organic nitriles such as PhCH2CN and C6H11CN, and organic isonitriles such as 2,6-Me2PhNC and C6H11NC, yielding the amido complex [{eta 5-1-(CH2Me2Si)-2,4-(Me3Si)2C5H2}{eta 5-1,2,4-(Me3Si)3C5H2}Th{N(p-tolyl)C(Ph)=CH(Ph)}] (3), five-membered heterocyclic complex [{eta 5-1-(p-tolyl)NC(Ph)=CHCC(Ph)CH2SiMe2-2,4-(Me3Si)2C5H2}{eta 5-1,2,4-(Me3Si)3C5H2}Th] (4), disulfido complex [{eta 5-1,2,4-(Me3Si)3C5H2}2Th(S2CPh2)] (6), iminato complexes [{eta 5-1,2,4-(Me3Si)3C5H2}2Th{eta 3-N(p-tolyl)C(CH2Ph)NH}(N=C=CHPh)] (8) and [{eta 5-1,2,4-(Me3Si)3C5H2}2Th{eta 3-N(p-tolyl)C(C6H11)NH}{N=C=C(CH2)5}] (9), eight-membered heterocyclic complex [{eta 5-1,2,4-(Me3Si)3C5H2}2Th{N(p-tolyl)C(=N-2,6-Me2Ph)C(H)=N(6-MePh-2-CH2)}] (11), and bis-amido complex [{eta 5-1,2,4-(Me3Si)3C5H2}2Th{1-C6H11-2,2-(CH2)5-4-(p-tolyl)N-5-C6H11N-(1,3-C4HN2)}] (12), respectively. Moreover, with chlorosilane PhSiH2Cl complex 2 converts to thorium amido chloride complex [{eta 5-1,2,4-(Me3Si)3C5H2}2Th(Cl){N(p-tolyl)SiH2Ph}] (13), demonstrating that the thorium imido fragment may also act as a nucleophile. Nevertheless, complex 2 may also initiate deprotonation reactions as shown by its reactivity with the imine (p-tolyl)2C=NH and thiazole to yield the amido-iminato complex [{eta 5-1,2,4-(Me3Si)3C5H2}2Th{NH(p-tolyl)}{N=C(p-tolyl)2}] (14) and amido thiazolyl compound [{eta 5-1,2,4-(Me3Si)3C5H2}2Th{NH(p-tolyl)}(C3H2NS)] (15), respectively. Last, but not the least, the cyclopentadienyl ligand [1,2,4-(Me3Si)3C5H2]- of 2 can also be protonated by the terminal alkyne PhC=CH, 1-indanone, and the nitrile Ph2CHCN to yield dimeric half-sandwich compounds [{{eta 5-1,2,4-(Me3Si)3C5H2}Th(C2Ph)(bipy)}2{mu-N(p-tolyl)}2] (5), [{{eta 5-1,2,4-(Me3Si)3C5H2}Th(1-O-CC8H7)(bipy)}2(mu-O)2] (7), and [{{eta 5-1,2,4-(Me3Si)3C5H2}Th(N=N=CPh2)(bipy)}2{mu-N(p-tolyl)}2] (10), respectively.

Halide exchange of (Cp-3tms)(2)ThCl2 (1; Cp-3tms = eta(5)-1,2,4-(Me3Si)(3)C5H2) with Me3SiI furnishes (Cp-3tms)(2)ThI2 (2), which is then reduced with potassium graphite (KC8) in the presence of 2,2 '-bipyridine to give the thorium bipyridyl metallocene (Cp-3tms)(2)Th(bipy) (3) in good yield. Complex 3 was fully characterized and readily reacted with various small molecules. For example, 3 may serve as a synthetic equivalent for the (Cp-3tms)(2)Th(II) fragment when exposed to CuI, Ph2S2, organic azides, and CS2. Moreover, upon the addition of thiobenzophenone Ph2CS, p-methylbenzaldehyde (p-MeC6H4)CHO, benzophenone Ph2CO, amidate PhCONH(p-tolyl), seleno-ketone (p,p '-dimethoxy), selenobenzophenone (p-MeOPh)(2)CSe, di(p-tolyl)methanimine (p-tolyl)(2)C & boxH;NH, 1,2-di(benzylidene)hydrazine (PhCH & boxH;N)(2), and nitriles PhCN, PhCH2CN, and Ph2CHCN C-C coupling results to give (Cp-3tms)(2)Th[(bipy)(Ph2CS)] (8), (Cp-3tms)(2)Th[(bipy)(p-MePhCHO)] (9), (Cp-3tms)(2)Th[(bipy)(Ph2CO)] (10), (Cp-3tms)(2)Th[(bipy){(p-tolylNH)(Ph)CO}] (11), (Cp-3tms)(2)Th[(bipy){(p-MeOPh)(2)CSe}] (12), (Cp-3tms)(2)Th[(bipy){(p-tolyl)(2)CNH}] (13), (Cp-3tms)(2)Th[(bipy)(PhCHNN & boxH;CHPh)] (14), (Cp-3tms)(2)Th[(bipy)(PhCN)] (16), (Cp-3tms)(2)Th[(bipy)(PhCH2CN)] (17), and (Cp-3tms)(2)Th[(bipy)(Ph2CHCN)] (18), respectively. However, when thiazole is added to 3, the dimeric sulfido complex [(Cp-3tms)(2)Th](2)[mu-(bipy)CH2NCHCHS](2) (15) can be isolated. Moreover, the addition of isonitriles such as Me3CNC and PhCH2NC to 3 results in C-N bond cleavage and C-C coupling processes to form the thorium isocyanido amido complexes (Cp-3tms)(2)Th[4-(Me3C)bipy](NC) (19) and (Cp-3tms)(2)Th[4-(PhCH2)bipy](NC) (20), respectively. Nevertheless, upon exposure of 3 to (trimethylsilyl)diazomethane Me3SiCHN2, the bis-amido complex (Cp-3tms)(2)Th[5,6-(Me3SiCH)bipy] (21), concomitant with N-2 release, is isolated.

A general synthetic procedure to neutral homo- and heterobimetallic cage compounds exhibiting various structural motifs of the polypnictogen ligands starting from [Cp*Fe(eta(5)-E-5)] (E = P (1), As (2); Cp* = C5Me5) is reported. The impact of the implemented transition metal precursors {Cp ''' M} (M = Cr, Mn, Fe, Ni; Cp ''' = 1,2,4-tBu(3)C(5)H(2)) emphasises the variability of the isolated complexes exhibiting a broad variety of structural motifs of the pnictogen ligands. Spectroscopic, crystallographic, and theoretical investigations provide insight into the structure of the partially unprecedented polypnictogen ligands.

The Lewis base-supported terminal uranium imido metallocene, [eta 5-1,3-(Me3Si)2C5H3]2U 00000000 00000000 00000000 00000000 11111111 00000000 11111111 00000000 00000000 00000000 N(mesityl)(dmap) (2), is readily accessible from the reaction of [eta 5-1,3-(Me3Si)2C5H3]2UMe2 (1) with mesitylNH2 in toluene in the presence of 4-dimethylaminopyridine (dmap). With compound 2 in hand, its reactivity towards small molecules was studied in detail. It reacts with terminal alkynes such as PhC 00000000000000000 00000000000000000 00000000000000000 01111111111111110 00000000000000000 01111111111111110 00000000000000000 01111111111111110 00000000000000000 00000000000000000 00000000000000000 CH to form the amido alkynyl complex [eta 5-1,3-(Me3Si)2C5H3]2U[N(mesityl)CHCHPh](CCPh) (3) exclusively. In the reaction with thio-ketone Ph2CS, CS2, isothiocyanate PhNCS and ketone Ph2CO, the initial [2 + 2] cycloaddition intermediates are too labile to be isolated, yielding [eta 5-1,3-(Me3Si)2C5H3]2U(S2CPh2)(dmap) (4) or dimeric sulfido and oxido complexes {[eta 5-1,3-(Me3Si)2C5H3]2U}2(mu-E)2 (E = S (5), O (6)), respectively. Moreover, complex 2 may also behave as a nucleophile in the reaction with bis(catecholato)diboron (B2cat2), yielding the amido catecholate complex [eta 5-1,3-(Me3Si)2C5H3]2U[N(mesityl)B(BO2C6H4)O(C6H4)O] (8). In addition, the imido moiety of 2 may also engage in deprotonation reactions as demonstrated by its reactivity with the carboxamide PhCONH(p-tolyl) and organic nitrile PhCH2CN, obtaining the uranium(iv) bis-amidate complex [eta 5-1,3-(Me3Si)2C5H3]2U[OC(Ph)N(p-tolyl)]2 (7) and the uranium(iv) iminato amido complex [eta 5-1,3-(Me3Si)2C5H3]2U[N(mesityl)C(CH2Ph)NH](NCCHPh) (9), respectively. Furthermore, 2 may also participate in single- and two-electron transfer processes. It is singly oxidized by CuI, Ph2S2, Ph2Se2 and Ph3CN3, yielding the uranium(v) imido complexes [eta 5-1,3-(Me3Si)2C5H3]2UN(mesityl)(X) (X = I (12), PhS (13), PhSe (14), and N3 (17)), or doubly oxidized by organic azides (RN3), forming the uranium(vi) bis-imido metallocenes [eta 5-1,3-(Me3Si)2C5H3]2UN(mesityl)(NR) (R = p-tolyl (15), mesityl (16)), respectively. Nevertheless, the addition of 1,2-diphenylhydrazine PhNHNHPh to complex 2 results in deprotonation and ligand elimination processes, yielding the uranium(v) bis-imido complex [eta 5-1,3-(Me3Si)2C5H3]U[NPh]2(dmap)3 (11) in the presence of dmap. The steric and electronic properties of coordinated cyclopentadienyl ligands significantly influence the reactivity of uranium imido metallocenes.

Characterization of paramagnetic compounds, in particular regarding the detailed conformation and electronic structure, remains a challenge, and - still today it often relies solely on the use of X-ray crystallography, thus limiting the access to electronic structure information. This is particularly true for lanthanide elements that are often associated with peculiar structural and electronic features in relation to their partially filled f-shell. Here, we develop a methodology based on the combined use of state-of-the-art magnetic resonance spectroscopies (EPR and solid-state NMR) and computational approaches as well as magnetic susceptibility measurements to determine the electronic structure and geometry of a paramagnetic Yb(III) alkyl complex, Yb(III)[CH(SiMe3)2]3, a prototypical example, which contains notable structural features according to X-ray crystallography. Each of these techniques revealed specific information about the geometry and electronic structure of the complex. Taken together, both EPR and NMR, augmented by quantum chemical calculations, provide a detailed and complementary understanding of such paramagnetic compounds. In particular, the EPR and NMR signatures point to the presence of three-centre-two-electron Yb-γ-Me-β–Si secondary metal-ligand interactions in this otherwise tri-coordinate metal complex, similarly to its diamagnetic Lu analogues. The electronic structure of Yb(III) can be described as a single 4f13 configuration, while an unusually large crystal-field splitting results in a thermally isolated ground Kramers doublet. Furthermore, the computational data indicate that the Yb-carbon bond contains some π-character, reminiscent of the so-called α-H agostic interaction.

The uranium bipyridyl metallocene, [eta 5-1,2,4-(Me3C)3C5H2]2U(bipy) (2), prepared from [eta 5-1,2,4-(Me3C)3C5H2]2UCl2 (1) and 2,2 '-bipyridine in the presence of potassium graphite (KC8) has been evaluated in small-molecule activation. In contact with AgF, Ph2E2 (E = S, Se), (PhNH)2, (PhCH=N)2, diazenes, pyridine N-oxide, organic azides, diazoalkanes, Ph2CS, and Ph2CO, it behaves as a synthon for the [eta 5-1,2,4-(Me3C)3C5H2]2U(II) fragment. In contrast, C-C bond coupling occurs when 2 is treated with (CH2)5CO, p-MePhCHO, and p-ClPhCHO to furnish [eta 5-1,2,4-(Me3C)3C5H2]2U[(bipy){(CH2)5CO}] (19), [eta 5-1,2,4-(Me3C)3C5H2]2U[(bipy)(p-MePhCHO)] (20), and [eta 5-1,2,4-(Me3C)3C5H2]2U[(bipy)(p-ClPhCHO)] (21), respectively. Moreover, a single-electron transfer (SET) process ensues after the addition of CuI to 2 to yield the uranium(III) iodide complex [eta 5-1,2,4-(Me3C)3C5H2]2UI (3). A comparison with the other uranium bipyridyl metallocene derivatives shows that minor variations in the coordinated cyclopentadienyl ligands changes the reactivity of these compounds.

The Lewis base-supported uranium terminal imido metallocene [η5-1,2,4-(Me3Si)3C5H2]2UN(p-tolyl)(dmap) (1) readily reacts with various small molecules such as internal alkynes, isothiocyanates, thioketones, amidates, organic nitriles and imines, chlorosilanes, copper iodide, diphenyl disulfide, organic azides and diazoalkane derivatives. For example, treatment of 1 with PhCCCCPh and PhNCS forms metallaheterocycles originating from a [2 + 2] cycloaddition to yield [η5-1-(p-tolyl)NC(Ph)CHCC(Ph)CH2Si(Me)2-2,4-(Me3Si)2C5H2][η5-1,2,4-(Me3Si)3C5H2]U (2) and [η5-1,2,4-(Me3Si)3C5H2]2U[N(p-tolyl)C(NPh)S](dmap) (3), respectively. The reaction of 1 with the thioketone Ph2CS forms the known uranium sulfido complex [η5-1,2,4-(Me3Si)3C5H2]2US(dmap) (4), which reacts with a second molecule of Ph2CS to give the disulfido compound [η5-1,2,4-(Me3Si)3C5H2]2U(S2CPh2) (5). The imido moiety also promotes deprotonation reactions as illustrated in the reactions with the amide PhCONH(p-tolyl), the nitrile PhCH2CN and the imine (p-tolyl)2CNH to form the bis-amidate [η5-1,2,4-(Me3Si)3C5H2]2U[OC(Ph)N(p-tolyl)]2 (7), and the iminato complexes [η5-1,2,4-(Me3Si)3C5H2]2U[N(p-tolyl)C(CH2Ph)NH](NCCHPh) (8) and [η5-1,2,4-(Me3Si)3C5H2]2U[NH(p-tolyl)][NC(p-tolyl)2] (9), respectively. Addition of PhSiH2Cl to 1 yields [η5-1,2,4-(Me3Si)3C5H2]2U(Cl)[N(p-tolyl)SiH2Ph] (10). In contrast, the uranium(V) imido complexes [η5-1,2,4-(Me3Si)3C5H2]2UN(p-tolyl)(I) (11) and [η5-1,2,4-(Me3Si)3C5H2]2UN(p-tolyl)(SPh) (12), may be isolated upon addition of CuI or Ph2S2 to 1, respectively. Uranium(VI) bis-imido metallocenes [η5-1,2,4-(Me3Si)3C5H2]2UN(p-tolyl)(NR) (R = p-tolyl (13), mesityl (14)) and [η5-1,2,4-(Me3Si)3C5H2]2UN(p-tolyl)[NN(9-C13H8)] (15) are accessible from 1 on exposure to RN3 (R = p-tolyl, mesityl) and 9-diazofluorene, respectively. Complexes 2, 3, 5, and 7-15 were characterized by various spectroscopic techniques and, in addition, compounds 2, 3, 5, and 7-13 were structurally authenticated by single-crystal X-ray diffraction analyses.

Terminal uranium oxido, sulfido, and selenido metallocenes were synthesized, and their reactivity was comprehensively studied. Heating of an equimolar mixture of [η5-1,2,4-(Me3Si)3C5H2]2UMe2 (2) and [η5-1,2,4-(Me3Si)3C5H2]2U(NH-p-tolyl)2 (3) in the presence of 4-dimethylaminopyridine (dmap) in refluxing toluene forms [η5-1,2,4-(Me3Si)3C5H2]2U═N(p-tolyl)(dmap) (4), which is a useful precursor for the preparation of the terminal uranium oxido, sulfido, and selenido metallocenes [η5-1,2,4-(Me3Si)3C5H2]2U═E(dmap) (E = O (5), S (6), Se (7)) employing a cycloaddition-elimination methodology with Ph2C═E (E = O, S) or (p-MeOPh)2CSe, respectively. Metallocenes 5-7 are inert toward alkynes, but they act as nucleophiles in the presence of alkylsilyl halides. The oxido and sulfido metallocenes 5 and 6 undergo [2 + 2] cycloadditions with isothiocyanate PhNCS or CS2, while the selenido derivative 7 does not. The experimental studies are complemented by density functional theory (DFT) computations.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The structure of and bonding in two base-free terminal actinide imido metallocenes, [η5-1,2,4-(Me3C)3C5H2]2An═N(p-tolyl) (An = U (1), Th (1')) are compared and connected to their individual reactivity. While structurally rather similar, the U(IV) derivative 1 is slightly more sterically crowded. Furthermore, density functional theory (DFT) studies imply that the 5f orbital contribution to the bonding within the individual actinide imido An═N(p-tolyl) moieties is significantly larger for 1 than for 1', which makes the bonds between the [η5-1,2,4-(Me3C)3C5H2]2U2+ and [(p-tolyl)N]2- fragments more covalent. Therefore, steric and electronic factors impact the reactivity of these imido complexes. For example, complex 1 is inert toward internal alkynes, but it readily forms Lewis base adducts [η5-1,2,4-(Me3C)3C5H2]2U═N(p-tolyl)(L) (L = OPMe3 (6), dmap (9), PhCN (14), and 2,6-Me2PhNC (17)) with Me3PO, 4-dimethylaminopyridine (dmap), nitrile, PhCN, or isonitrile 2,6-Me2PhNC. It may also react as a nucleophile or undergo a [2 + 2] cycloaddition with CS2, isothiocyanates, thio-ketones, ketones, lactides, and acyl nitriles, forming the four- or five-membered metallaheteroacycles, terminal sulfido, or oxido complexes, and cyanide amidate complexes, respectively. In contrast, after the addition of aldehyde p-tolylCHO, the tetranuclear complex [η5-1,2,4-(Me3C)3C5H2]4[OCH(p-tolyl)CH(p-tolyl)O]2U4O4 (10) is isolated. However, while 1 is unreactive toward dicyclohexylcarbodiimide (DCC), an equilibrium exists in benzene solution between N,N'-diisopropylcarbodiimide (DIC), 1, and the four-membered metallaheterocycle [η5-1,2,4-(Me3C)3C5H2]2U[N(p-tolyl)C(═NiPr)N(iPr)] (12). Furthermore, 1 may also engage in single- and two-electron transfer processes. It is singly oxidized by Ph3CN3, CuI, Ph2S2, and Ph2Se2, yielding the uranium(V) imido complexes [η5-1,2,4-(Me3C)3C5H2]2U═N(p-tolyl)(X) (X = N3 (20), I (22), PhS (23), and PhSe (24)), or is doubly oxidized by organic azides (RN3) and 9-diazofluorene, forming the uranium(VI) bis-imido metallocenes [η5-1,2,4-(Me3C)3C5H2]2U═N(p-tolyl)(=NR) (R = p-tolyl (18), mesityl (19)) and [η5-1,2,4-(Me3C)3C5H2]2U=N(p-tolyl)[=NN=(9-C13H8)] (21), respectively.

Addition of p-tolylNH(2) to a toluene solution of [eta(5)-1,3-(Me3C)(2)C5H3](2)UMe2 (1) in the presence of 4-dimethylaminopyridine (dmap) yields the Lewis base-supported terminal uranium imido metallocene, [eta(5)-1,3-(Me3C)(2)C5H3](2)U=N(p-tolyl)(dmap) (2), concomitant with methane release. Complex 2 undergoes a [2 + 2] cycloaddition with internal alkynes such as PhC equivalent to CMe to form [eta(5)-1,3-(Me3C)(2)C5H3](2)U[N(p-tolyl)C(Me)=C(Ph)] (3) exclusively. Formal [2 + 2] cycloadditions also initiate the reactions of complex 2 with ketones, thio-ketones, CS2, isothiocyanates, and seleno-ketones, but these [2 + 2] cycloaddion products are too unstable to be isolated, yielding dimeric oxido, sulfido, and selenido complexes, respectively. In the reaction with esters, carbodiimides, acyl nitriles, chlorosilanes, and bis(catecholato)diboron (B(2)cat(2)), uranium(IV) alkoxido amidate, guanidato, amidinato cyanido, amido chloride, and amido catecholate complexes are formed, respectively, indicating that this imido moiety may also act as a nucleophile. Moreover, the imido moiety in complex 2 may also engage in deprotonation reactions, as shown by its reactivity with the carboxamide PhCONH(p-tolyl), the organic nitriles PhCH2CN, Ph2CHCN, PhCN, and 1,4-(CH2)(4)(CN)(2) to yield the uranium(IV) bis-amidate [eta(5)-1,3-(Me3C)(2)C5H3](2)U[OC(Ph)N(p-tolyl)](2) (8), the uranium(IV) iminato amido complexes [eta(5)-1,3-(Me3C)(2)C5H3](2)U[N(p-tolyl)=C(CH2Ph)NH](N=C=CHPh) (11), [eta(5)-1,3-(Me3C)(2)C5H3](2)U[N(p-tolyl)=C(CHPh2)NH](N=C=CPh2) (12), and [eta(5)-1-{N=C(Ph)N=C(Ph)}-2,4-(Me3C)(2)C5H2][eta(5)-1,3-(Me3C)(2)C5H3]U[N(p-tolyl)=C(Ph)NH] (15), and the dimeric uranium(IV) imido {[eta(5)-1,3-(Me3C)(2)C5H3](2)U=N(C5H6)CN}(2) (13), respectively. Furthermore, 2 may also be doubly oxidized with organic azides (RN3), forming the uranium(VI) bis-imido metallocenes [eta(5)-1,3-(Me3C)(2)C5H3](2)U=N(p-tolyl)(=NR) (R = p-tolyl (19), mesityl (20)). Nevertheless, addition of Ph2S2 or Ph2Se2 to complex 2 results in ligand redistribution processes, yielding the uranium(VI) bis-imido complexes U[=N(p-tolyl)](2)(SPh)(2)(dmap)(2) (21) and [eta(5)-1,3-(Me3C)(2)C5H3]U[=N(p-tolyl)](2)(SePh)(dmap)(2) (22) in low yield, respectively.

Uranium diazomethanediide complexes can be prepared and their synthesis, structure and reactivity were explored. Reaction of the uranium imido compound [ η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 ] 2 U=N( p -tolyl)(dmap) ( 1 ) or [ η 5 -1,3-(Me 3 C) 2 C 5 H 3 ] 2 U=N( p -tolyl)(dmap) ( 4 ) with Me 3 SiCHN 2 cleanly yields the first isocyanoimido metal complexes [ η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 ] 2 U(=NNC)( μ -CNN=)U(dmap)[ η 5 -1,2,4-(Me 3 Si) 3 C 5 H 2 ] 2 ( 2 ) and {[ η 5 -1,3-(Me 3 C) 2 C 5 H 3 ] 2 U[ μ -(=NNC)]} 6 ( 5 ), respectively. Both compounds exhibit remarkable thermal stability and were fully characterized. According to density functional theory (DFT) studies the bonding between the Cp 2 U 2+ and [NNC] 2− moieties is strongly polarized with a significant 5 f orbital contribution, which is also reflected in the reactivity of these complexes. For example, complex 5 acts as a nucleophile toward alkylsilyl halides and engages in a [2+2] cycloaddition with CS 2 , but no reaction occurs in the presence of internal alkynes.