Tough, Eu3+ -Induced Luminescent Hydrogel as Flexible Chemosensor for Real-Time Quantitative Detection of Zn2+ Ion.

Herein, a novel tough luminescent hydrogel with Europium is fabricated using a facile copolymerization process by introducing 2,2':6',2-terpyridine (TPy) into a dual physical cross-linked hydrogel. The obtained P(NAGA-co-MAAc)/Eu/TPy (x) (x refers to the feed ratio of NAGA to MAAc) hydrogels not only show outstanding mechanical performances (fracture strength, ≈2.5 MPa), but also give a special ability of rapid detection to low concentrations of zinc ions. Attractively, the theoretical limits of detection (LOD) of the hydrogel sensors are calculated as 1.6 µm, which is acceptable within the WHO limit. Furthermore, the continuous change in fluorescence of P(NAGA-co-MAAc)/Eu/TPy (10) strips upon contact with Zn2+ can be clearly observed by the naked eyes with the aid of a portable UV lamp, resulting in semi-quantitative naked-eyes detection through a standard colorimetric card. Moreover, by identifying the RGB value of the hydrogel sensor, it can also realize quantitative analysis. Therefore, excellence in sensing, simplicity in structure, and convenience in using make P(NAGA-co-MAAc)/Eu/TPy (10) hydrogel as a superior fluorescent chemosensor of Zn2+ ions.

A 2,2'-bipyridyl calcium complex: synthesis, structure and reactivity studies.

A 2,2'-bipyridyl calcium complex based on a tridentate ligand [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca(bipy)(THF) (1) was prepared by the reduction of {[CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]CaI(THF)}2 with potassium graphite in the presence of 2,2'-bipyridine (bipy). Complex 1 is a good Ca(I)synthon, as shown by its reactivity with I2, PhCH2SSCH2Ph, PhCH2SeSeCH2Ph and 9-fluorenone, yielding the calcium iodide complex [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]CaI(bipy) (2), calcium thiolate [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca(SCH2Ph)(bipy) (3), calcium selenolate [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca(SeCH2Ph)(bipy) (4), and calcium ketyl complex [CH3C(N-2,6-iPr2C6H3)CHC(CH3)NCH2CH2N(CH3)2]Ca[O-(9-C13H8˙)](bipy)·2THF (5·2THF), respectively. In addition, reactions of complex 5 with CS2, CH2CHCH2Br and PhCH2Br give the corresponding dimeric bis(thiolate) complex {[S2CC(CMe(NAr))C(Me)NCH2CH2NMe2]Ca(DME)}2 (6), dimeric calcium bromide complex {[(9-CH2CHCH2-C13H8-9)-O]CaBr(THF)(bipy)}2 (7) and {[(9-C6H5CH2-C13H8-9)-O]CaBr[O-(9-C13H8)](bipy)}2 (8). These results demonstrated that the calcium ketyl complex 5 can also be employed as a single-electron transfer reagent. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.

Azobenzenyl Calcium Complex: Synthesis and Reactivity Studies of a Ca(I) Synthon.

Attempted preparation of a low-valent Ca(I) complex by reduction of Ca iodide precursor [LCaI(THF)]2 (1) (L = [CH3C(NAr)CHC(CH3)NCH2CH2N(CH3)2]-, Ar = 2,6-iPr2C6H3), with KC8 led to isolation of a dinuclear calcium azaallyl complex {[H2CC(NAr)CHC(CH3)(NCH2CH2N(CH3)2)]Ca(THF)}2 (2). Alternatively, reaction of 1 with KC8 in the presence of azobenzene gives an azobenzenyl calcium complex LCa(PhNNPh)(THF) (3). The electron paramagnetic resonance and UV-vis spectra of complex 3 suggest that the (PhNNPh) moiety should be regarded as a radical anion. Complex 3 can react with Me3SiN3, Me3SiCHN2, CS2, W(CO)6, elemental sulfur, and AgBr, resulting in the formation of the azido complex [LCaN3(THF)]2 (5), isonitril complex {LCa[CNN(Si(CH3)3)]}2 (6), dimeric bis(thiolate) complex {[S2CC(CMe(NAr))C(Me)NCH2CH2NMe2]Ca(DME)}2 (7), metallocyclic carbene complex {[OC(W(CO)5)N(C6H5)]Ca(THF)3}2 (8), bis(thiolate) complex {[S2C(CMe(NAr))C(Me)NCH2CH2NMe2]Ca(THF)}2 (9), and bromide complex [LCaBr(THF)]2 (10). Additional insights on the reaction process resulting in the formation of complex 7 are provided by density-functional theory studies. These results demonstrate that the (PhNNPh)•- radical anion can serve as a very potent one-electron donor, and 3 acts as a low-valent calcium(I) synthon.

Reactivity studies on lanthanum and cerium hydrido metallocenes.

Alkyl complexes [η5-1,3-(Me3C)2C5H3]2Ln(CH2C6H4-o-NMe2) (Ln = La 1 and Ce 2) react with 9-borabicyclo[3.3.1]nonane (9-BBN) in THF to afford the lanthanum boroxide complex [η5-1,3-(Me3C)2C5H3]2La(µ-OBC8H14)(THF) (3) and cerium boroxide complex [η5-1,3-(Me3C)2C5H3]2Ce(µ-OBC8H14)(THF) (4). However, the reaction of alkyl complexes [η5-1,3-(Me3C)2C5H3]2Ln(CH2C6H4-o-NMe2) with cyclohexene oxide followed by the addition of 9-BBN resulted in the formation of ring-opened products [η5-1,3-(Me3C)2C5H3]2Ln(OC6H11)(THF) (Ln = La 5 and Ce 6) concomitant with C8H14BCH2C6H4N(CH3)2 release, indicating that lanthanum and cerium hydride complexes formed in situ by treating alkyl complexes with 9-BBN may be the reactive species. Therefore, further studies on the reactivity of lanthanum and cerium hydride complexes generated in situ were carried out. The reaction of lanthanum and cerium hydride complexes with Me3SiCl provided lanthanide chloride complexes [η5-1,3-(Me3C)2C5H3]2LnCl (Ln = La 7and Ce 8) as well as Me3SiH. Each lanthanide hydride complex reduces phenazine and white phosphorus to produce {[η5-1,3-(Me3C)2C5H3]2Ln}2(µ-η3:η3-C12H8N2) (Ln = La 9 and Ce 10) and {[η5-1,3-Me3C)2C5H3]2Ln}3P7 (Ln = La 11 and Ce 12), respectively. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.

Discovery of polypyridyl iridium(III) complexes as potent agents against resistant Candida albicans.

The increasing emergence and spread of drug resistant Candida albicans represent a serious challenge for effective treatment and call for the development of new therapeutic options. To address this need, we synthesized a series of polypyridyl iridium(III) complexes and studied their antimicrobial activities. Herein, one lead iridium(III) complex Ir-3 [(ptpy)2Ir(dppz)]PF6, with ptpy = 2-(p-tolyl)pyridine and dppz = dipyrido[3,2-a:2',3'-c]phenazine, exhibited potent and broad-spectrum antifungal activities against drug-resistant pathogens and low hemolytic activity toward mammalian cells. Furthermore, Ir-3 showed low tendency to induce resistance, displayed biofilm inhibition and eradication activities. Significantly, Ir-3 exhibited potent in vivo antifungal activity in a murine model of disseminated candidiasis. This study may pave the way for the development of novel antifungal agent based upon polypyridyl iridium(III) complex to combat antifungal resistance.

Cerocene and Lanthanocene Chalcogenides: Synthesis, Structure, and Luminescence.

A series of lanthanide chalcogenides {[η5-1,3-(Me3C)2C5H3]2Ln}2(µ-η2:η2-Te2) (Ln = Ce 1, La 2), {[η5-1,3-(Me3C)2C5H3]2Ln(THF)}2(µ-Se) (Ln = Ce 3, La 4), and {[η5-1,3-(Me3C)2C5H3]2Ln(THF)}2(µ-Te) (Ln = Ce 5, La 6) can be readily obtained by the reaction of the alkyl complexes [η5-1,3-(Me3C)2C5H3]2Ln(CH2C6H4-o-NMe2) with elemental selenium or tellurium in the presence of 9-borabicyclo[3.3.1]nonane (9-BBN). The reaction of the alkyl complexes [η5-1,3-(Me3C)2C5H3]2Ln(CH2C6H4-o-NMe2) with 9-BBN in 1:2 molar ratio afforded the lanthanide (cyclooctane-1,5-diyl)dihydroborate complexes [η5-1,3-(Me3C)2C5H3]2Ln[(µ-H)2BC8H14] (Ln = Ce 7, La 8) concomitant with the (Me2N-o-C6H4CH2)BC8H14 release, indicating that [η5-1,3-(Me3C)2C5H3]2LnH may be the reactive species for the synthesis of lanthanide chalcogenides. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses. Luminescence spectroscopy was also employed to characterize complexes 1-6. The Ce(III) complexes 3 and 5 display distinct luminescence properties at room temperature, as compared to the corresponding La(III) complexes 4 and 6. The complex {[η5-1,3-(Me3C)2C5H3]2Ce(THF)}2(µ-Te) (5) exhibits unexpectedly red emission in solution which is found to depend strongly on the excitation wavelength.

Lanthanocene and Cerocene Alkyl Complexes: Synthesis, Structure, and Reactivity Studies.

Lanthanocene and cerocene alkyl complexes [η5-1,3-(Me3C)2C5H3]2Ln(CH2C6H4-o-NMe2) (Ln = La 3 and Ce 4) were obtained from the salt metathesis of {[η5-1,3-(Me3C)2C5H3]2Ln(µ3-κ3-O3SCF3)2K(THF)2}2·THF (Ln = La 1·THF and Ce 2·THF) with LiCH2C6H4-o-NMe2. Reactivity of 3 and 4 toward various small molecules provides access to a series of lanthanide derivatives. For example, reactions of 3 and 4 with elemental chalcogens (sulfur and selenium) in 1:1 molar ratio give the lanthanide thiolates {[η5-1,3-(Me3C)2C5H3]2Ln(µ-SCH2C6H4-o-NMe2)}2 (Ln = La 5 and Ce 6) and selenolates {[η5-1,3-(Me3C)2C5H3]2Ln(µ-SeCH2C6H4-o-NMe2)}2 (Ln = La 7 and Ce 8). The compounds 3 and 4 react with two equivalents of elemental chalcogens (sulfur and selenium) to afford the lanthanide disulfides {[η5-1,3-(Me3C)2C5H3]2Ln}2(µ-η2:η2-S2) (Ln = La 9 and Ce 10) and diselenides {[η5-1,3-(Me3C)2C5H3]2Ln}2(µ-η2:η2-Se2) (Ln = La 11 and Ce 12). The lanthanide disulfides (9 and 10) or diselenides (11 and 12) can also be readily obtained through oxidation of the corresponding lanthanide thiolates (5 and 6) or selenolates (7 and 8) by elemental chalcogens concomitant with the (Me2N-o-C6H4CH2)2E2 (E = S or Se) release. Treatment of 3 and 4 with one equivalent or two equivalents of benzonitrile produces the serendipitous lanthanum and cerium-1-azaallyl complexes [η5-1,3-(Me3C)2C5H3]2Ln[N(H)C(Ph)═CHC6H4-o-NMe2] (Ln = La 13 and Ce 14) or amidine complexes [η5-1,3-(Me3C)2C5H3]2Ln[N(H)C(Ph)NC(Ph)═CHC6H4-o-NMe2]·C7H8 (Ln = La 15·C7H8 and Ce 16·C7H8), respectively. The compound 15 or 16 can also be readily synthesized by further insertion of one benzonitrile molecule into the 1-azaallyl complex 13 or 14. Insertion of N,N'-dicyclohexylcarbodiimide or phenyl isothiocyanate into Ln-C bonds within 3 and 4 results in the formation of the amidine complexes [η5-1,3-(Me3C)2C5H3]2Ln[CyNC(CH2C6H4-o-NMe2)NCy] (Cy = cyclohexyl, Ln = La 17 and Ce 18) or thioamidato complexes [η5-1,3-(Me3C)2C5H3]2Ln[SC(CH2C6H4-o-NMe2)NPh] (Ln = La 19 and Ce 20). All of the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.

Reactivity of a ß-diketiminate-supported magnesium alkyl complex toward small molecules.

The reactivity of the magnesium alkyl {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(nBu)}2 (1) toward various small molecules provides access to a variety of magnesium derivatives. For example, the insertion of elemental chalcogens (S8 and Se8) into the Mg-C bond of complex 1 gives the dimeric magnesium thiolate {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(µ-SnBu)}2 (2), magnesium selenolate [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(SenBu)(THF) (3), and magnesium diselenolate [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(Se2nBu)(THF) (4). Meanwhile, compound 4 can be readily obtained by further insertion of one selenium atom into complex 3. Moreover, the reactions of complex 1 with diphenyl dichalcogenides (PhSSPh and PhSeSePh) by σ bond metathesis afford the corresponding magnesium phenyl chalcogenolates [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(EPh)(THF) (E = S 5, Se 6) concomitant with PhEnBu release. Furthermore, the treatment of complex 1 with benzonitrile and phenyl isothiocyanate produces the serendipitous magnesium-1-azaallyl complex [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(N(H)C(Ph)[double bond, length as m-dash]CHC3H7)(DME) (7) and the diimino-thioamidato magnesium compound {κ3-N,N',N''-(ArNCMe)2[N(Ph)CS]CH}Mg[(Ph)NC(nBu)S] (8) (Ar = 2,6-iPr2C6H3). In addition, deprotonation occurs between compound 1 and 1-methylimidazole to generate the imidazolyl complex {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(µ-Im)}2 (9) (Im = 2-N-methylimidazolyl). These results indicated that the butylmagnesium complex 1 possesses high activity toward small molecules and revealed several unusual transformations. All the new compounds were characterized by various spectroscopic methods, and their solid-state structures were further confirmed by single-crystal X-ray diffraction analyses.

An Azobenzenyl Anion Radical Complex of Magnesium: Synthesis, Structure, and Reactivity Studies.

Azobenzenyl anion radical complex of magnesium [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(PhNNPh) (THF) (2) was obtained for the first time through the reaction of [HC(C(Me)N-2,6-iPr2C6H3)2]MgBr (1) with potassium graphite in the presence of azobenzene. Complex 2 is a useful electron-transfer reagent as shown by the reactivity with diphenyl disulfide, diphenyl diselenide, oxygen, sulfur, and Me3SiN3 yielding the magnesium thiolate [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(SPh)(THF) (3), magnesium selenolate [HC(C(Me)N-2,6-iPr2C6H3)2]Mg(SePh)(THF) (4), peroxido complex {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(THF)}2(µ-η2-η2-O2) (5), persulfido complex {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg(THF)}2(µ-η2-η2-S2) (6), and azido complex [HC(C(Me)N-2,6-iPr2C6H3)2]MgN3 (7), respectively. Furthermore, treatment of 2 with Me3SiCHN2 results in a rearrangement product {[HC(C(Me)N-2,6-iPr2C6H3)2]Mg[CNN(SiMe3)]}2 (8).

An actinide metallacyclopropene complex: synthesis, structure, reactivity, and computational studies.

The synthesis, structure, and reactivity of an actinide metallacyclopropene were comprehensively studied. The reduction of [η(5)-1,2,4-(Me3C)3C5H2]2ThCl2 (1) with potassium graphite (KC8) in the presence of diphenylacetylene (PhC≡CPh) yields the first stable actinide metallacyclopropene [η(5)-1,2,4-(Me3C)3C5H2]2Th(η(2)-C2Ph2) (2). The magnetic susceptibility data show that 2 is indeed a diamagnetic Th(IV) complex, and density functional theory (DFT) studies suggest that the 5f orbitals contribute to the bonding of the metallacyclopropene Th-(η(2)-C═C) moiety. Complex 2 shows no reactivity toward alkynes, but it reacts with a variety of heterounsaturated molecules such as aldehyde, ketone, carbodiimide, nitrile, organic azide, and diazoalkane derivatives. DFT studies complement the experimental observations and provide additional insights. Furthermore, a comparison between Th and group 4 metals reveals that Th(4+) shows unique reactivity patterns.

Experimental and computational studies on the reactivity of a terminal thorium imidometallocene towards organic azides and diazoalkanes.

The reaction of the base-free terminal thorium imido complex [{η(5)-1,2,4-(Me3C)3C5H2}2Th=N(p-tolyl)] (1) with p-azidotoluene yielded irreversibly the tetraazametallacyclopentene [{η(5)-1,2,4-(Me3C)3C5H2}2Th{N(p-tolyl)N=N-N(p-tolyl)}] (2), whereas the bridging imido complex [{[η(5)-1,2,4-(Me3C)3C5H2]Th(N3)2}2{µ-N(p-tolyl)}2][(n-C4H9)4N]2 (3) was isolated from the reaction of 1 with [(n-C4H9)4N]N3. Unexpectedly, upon the treatment of 1 with 9-diazofluorene, the NN bond was cleaved, an N atom was transferred, and the η(2)-diazenido iminato complex [{η(5)-1,2,4-(Me3C)3C5H2}2Th{η(2)-[N=N(p-tolyl)]}{N=(9-C13H8)}] (4) was formed. In contrast, the reaction of 1 with Me3SiCHN2 gave the nitrilimido complex [{η(5)-1,2,4-(Me3C)3C5H2}2Th{NH(p-tolyl)}{N2CSiMe3}] (5), which slowly converted into [{η(5)-1,2,4-(Me3C)3C5H2}{η(5):κ-N-1,2-(Me3C)2-4-CMe2(CH2NN=CHSiMe3)C5H2}Th{NH(p-tolyl)}] (6) by intramolecular C-H bond activation. The experimental results are complemented by density functional theory (DFT) studies.

(2,2'-Bipyridine-κ(2) N,N')[bis-(diphenyl-thio-phosphino-yl)meth-yl]lithium(I) benzene monosolvate.

In the title benzene-solvated heteroleptic lithium complex, [Li(C25H21P2S2)(C10H8N2)]·C6H6, the Li(I) ion is four-coordinated in a distorted tetra-hedral geometry by two S atoms and two N atoms of the two chelating ligands, viz. bis-(diphenyl-thio-phosphino-yl)methyl and 2,2'-bipyridine. The 2,2'-bipyridine mol-ecule is slightly twisted with a dihedral angle between the pyridine rings of 7.35 (12)°. Intra-molecular C-H⋯S hydrogen bonds are present. In the crystal, mol-ecules are stacked along the c axis by π-π inter-actions, with centroid-centroid distances of 3.6021 (15) and 3.6401 (16) Å. The crystal structure also features weak C-H⋯π inter-actions.

A bipyridyl thorium metallocene: synthesis, structure and reactivity.

The synthesis, structure and reactivity of a new bipy thorium metallocene have been studied. The reduction of the thorium chloride metallocene [η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)ThCl(2) (1) with potassium graphite in the presence of 2,2'-bipyridine gives the purple bipy metallocene [η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)Th(bipy) (2) in good yield. Complex 2 has been fully characterized by various spectroscopic techniques, elemental analysis and X-ray diffraction analysis. Complex 2 reacts cleanly with trityl chloride, silver halides and diphenyl diselenide, leading to the halide metallocenes [η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)ThX(2) (X = Cl (1), Br (3), I (4)) and [η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)Th(F)(µ-F)(3)Th[η(5)-1,3-(Me(3)C)(2)C(5)H(3)](F)(bipy) (5), and selenido metallocene [η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)Th(SePh)(2) (6), in good conversions. In addition, 2 cleaves the C[double bond, length as m-dash]S bond of CS(2) to give the sulfido complex, [η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)ThS (7), which further undergoes an irreversible dimerization or nucleophilic addition with CS(2), leading to the dimeric sulfido complex {[η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)Th}(µ-S)(2) (8) and dimeric trithiocarbonate complex {[η(5)-1,3-(Me(3)C)(2)C(5)H(3)](2)Th}(µ-CS(3))(2) (10) in good yields, respectively.

A base-free thorium-terminal-imido metallocene: synthesis, structure, and reactivity.

The synthesis, structure, and reactivity of a base-free thorium terminal-imido metallocene have been comprehensively studied. Treatment of thorium metallocenes [{η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)}(2)ThMe(2)] and [{η(5)-1,3-(Me(3)C)(2)C(5)H(3)}(2)ThMe(2)] with RNH(2) gives diamides [{η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)}(2)Th(NHR)(2)] (R=Me (7), p-tolyl (8)) and [{η(5)-1,3-(Me(3)C)(2)C(5)H(3)}(2)Th(NH-p-tolyl)(2)] (9), respectively. Diamides 7 and 9 do not eliminate methylamine or p-toluidine, but sublime without decomposition at 150 °C under vacuum (0.01 mmHg), whereas diamide 8 is converted at 140 °C/0.01 mmHg into the primary amine p-tolyl-NH(2) and [{η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)}(2)Th=N(p-tolyl)] (10), which may be isolated in pure form. Imido metallocene 10 does not react with electrophiles such as alkylsilyl halides; however, it reacts with electron-rich or unsaturated reagents. For example, reaction of 10 with sulfur affords the metallacycle [{η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)}(2)Th{N(p-tolyl)S-S}]. Imido 10 is an important intermediate in the catalytic hydroamination of internal alkynes, and an efficient catalyst for the trimerization of PhCN. Density functional theory (DFT) studies provide a detailed understanding of the experimentally observed reactivity patterns.

The Th=C double bond: an experimental and computational study of thorium poly-carbene complexes.

The first thorium poly-carbene complexes [(Ph(2)P=S)(2)C](2)Th(DME) (2) and [{[(Ph(2)P=S)(2)C](3)Th}Li(2)(DME)](n) (3) have been prepared and structurally characterized. DFT calculations reveal that the Th=C bond is polarized toward the nucleophilic carbene carbon atom, which is further verified by the experimental observation that the Th=C bond shows a nucleophilic behavior with Ph(2)CO.

Thorium oxo and sulfido metallocenes: synthesis, structure, reactivity, and computational studies.

The synthesis, structure, and reactivity of thorium oxo and sulfido metallocenes have been comprehensively studied. Heating of an equimolar mixture of the dimethyl metallocene [η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)](2)ThMe(2) (2) and the bis-amide metallocene [η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)](2)Th(NH-p-tolyl)(2) (3) in refluxing toluene results in the base-free imido thorium metallocene, [η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)](2)Th═N(p-tolyl) (4), which is a useful precursor for the preparation of oxo and sulfido thorium metallocenes [η(5)-1,2,4-(Me(3)C)(3)C(5)H(2)](2)Th═E (E = O (5) and S (15)) by cycloaddition-elimination reaction with Ph(2)C═E (E = O, S) or CS(2). The oxo metallocene 5 acts as a nucleophile toward alkylsilyl halides, while sulfido metallocene 15 does not. The oxo metallocene 5 and sulfido metallocene 15 undergo a [2 + 2] cycloaddition reaction with Ph(2)CO, CS(2), or Ph(2)CS, but they show no reactivity with alkynes. Density functional theory (DFT) studies provide insights into the subtle interplay between steric and electronic effects and rationalize the experimentally observed reactivity patterns. A comparison between Th, U, and group 4 elements shows that Th(4+) behaves more like an actinide than a transition metal.