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Uranium diazomethanediide complexes can be prepared and their synthesis, structure and reactivity were explored. Reaction of the uranium imido compound [η5‐1,2,4‐(Me3Si)3C5H2]2U=N(p‐tolyl)(dmap) (1) or [η5‐1,3‐(Me3C)2C5H3]2U=N(p‐tolyl)(dmap) (4) with Me3SiCHN2 cleanly yields the first isocyanoimido metal complexes [η5‐1,2,4‐(Me3Si)3C5H2]2U(=NNC)(μ‐CNN=)U(dmap)[η5‐1,2,4‐(Me3Si)3C5H2]2 (2) and {[η5‐1,3‐(Me3C)2C5H3]2U[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 Cp2U2+ 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 CS2, but no reaction occurs in the presence of internal alkynes. [ABSTRACT FROM AUTHOR]

The synthesis, electronic structure, and reactivity of a uranium metallacyclopropene were comprehensively studied. Addition of diphenylacetylene (PhC≡CPh) to the uranium phosphinidene metallocene [η5‐1,2,4‐(Me3C)3C5H2]2U=P‐2,4,6‐tBu3C6H2 (1) yields the stable uranium metallacyclopropene, [η5‐1,2,4‐(Me3C)3C5H2]2U[η2‐C2Ph2] (2). Based on density functional theory (DFT) results the 5f orbital contributions to the bonding within the metallacyclopropene U‐(η2‐C=C) moiety increases significantly compared to the related ThIV compound [η5‐1,2,4‐(Me3C)3C5H2]2Th[η2‐C2Ph2], which also results in more covalent bonds between the [η5‐1,2,4‐(Me3C)3C5H2]2U2+ and [η2‐C2Ph2]2− fragments. Although the thorium and uranium complexes are structurally closely related, different reaction patterns are therefore observed. For example, 2 reacts as a masked synthon for the low‐valent uranium(II) metallocene [η5‐1,2,4‐(Me3C)3C5H2]2UII when reacted with Ph2E2 (E=S, Se), alkynes and a variety of hetero‐unsaturated molecules such as imines, ketazine, bipy, nitriles, organic azides, and azo derivatives. In contrast, five‐membered metallaheterocycles are accessible when 2 is treated with isothiocyanate, aldehydes, and ketones. [ABSTRACT FROM AUTHOR]

The first stable base‐free terminal uranium phosphinidene metallocene is presented; and its structure and reactivity have been studied in detail and compared to that of the corresponding thorium derivative. Salt metathesis reaction of the methyl iodide uranium metallocene Cp"'2U(I)Me (2, Cp"'=η5‐1,2,4‐(Me3C)3C5H2) with Mes*PHK (Mes*=2,4,6‐(Me3C)3C6H2) in THF yields the base‐free terminal uranium phosphinidene metallocene, Cp"'2U=PMes* (3). In addition, density functional theory (DFT) studies suggest substantial 5f orbital contributions to the bonding within the uranium phosphinidene [U]=PAr moiety, which results in a more covalent bonding between the [Cp"'2U]2+ and [Mes*P]2− fragments than that for the related thorium derivative. This difference in bonding besides steric reasons causes different reactivity patterns for both molecules. Therefore, the uranium derivative 3 may act as a Cp"'2U(II) synthon releasing the phosphinidene moiety (Mes*P:) when treated with alkynes or a variety of hetero‐unsaturated molecules such as imines, thiazoles, ketazines, bipy, organic azides, diazene derivatives, ketones, and carbodiimides. [ABSTRACT FROM AUTHOR]

The KCl-bridged phosphinidiide thorium metallocene, {[η5-1,3-(Me3C)2C5H3]2Th(=P-2,4,6-iPr3C6H2)(ClK)}2 (2), was isolated in good yield by a salt metathesis reaction of the thorium methyl chloride compound [η5-1,3-(Me3C)2C5H3]2Th(Cl)Me (1) with 2,4,6-iPr3C6H2PHK in toluene. Furthermore, it was fully characterized including its molecular structure. The reactivity of 2 towards various small organic molecules was also explored, e.g., it reacts with alkynes, nitriles, CS2, quinolines, silanes, pyridine and imidazole derivatives, resulting in metallacycles, imidos, carbodithiolates, and phosphido compounds. Density functional theory (DFT) computations were conducted to supplement the experimental investigations. [ABSTRACT FROM AUTHOR]

A three-membered thorium metallaheterocycle [η5-1,3-(Me3C)2C5H3]2Th[η2-P2(2,4,6-iPr3C6H2)2] (4) is readily prepared besides H2 from [η5-1,3-(Me3C)2C5H3]2Th(PH-2,4,6-iPr3C6H2)2 (3) upon heating in toluene solution. Density functional theory (DFT) studies were performed to elucidate the 5f orbital contribution to the bonding within Th-(η2-P-P) revealing more covalent bonds between the [η5-1,3-(Me3C)2C5H3]2Th2+ and [η2-P2(2,4,6-iPr3C6H2)2]2− fragments than those in the related thorium metallacyclopropene. Consequently, distinctively different reactivity patterns emerge, e.g., while 4 reacts with pyridine derivatives such as 4-dimethyaminopyridnie (DMAP) and forms the DMAP adduct [η5-1,3-(Me3C)2C5H3]2Th[η2-P2(2,4,6-iPr3C6H2)2](DMAP) (5), it may also act as a [η5-1,3-(Me3C)2C5H3]2Th(II) synthon when reacted with bipy, Ph2S2 or Ph2Se2. Nevertheless, no reaction of complex 4 with alkynes is observed, but it reacts as a nucleophile towards nitriles and aldehydes resulting in five- or seven-membered metallaheterocycles, respectively. DFT computations provide some additional insights into the experimental observations. [ABSTRACT FROM AUTHOR]

The synthesis, structure, and reactivity of a thorium metallacyclopentadiene were comprehensively studied. The reduction of (η5-C5Me5)2ThCl2 (1) with potassium graphite (KC8) in the presence of diphenylacetylene (PhC≡CPh) yields the first thorium metallacyclopentadiene complex (η5-C5Me5)2Th(η2-C4Ph4) (2). Density functional theory (DFT) studies suggest that the 5f orbitals are involved in the bonding of the metallacyclopentadiene Th–(η2-C=C–C=C) moiety. Compared to the thorium metallacyclopropene, complex 2 shows a distinctively different reactivity towards diazoalkanes and organic azides such as Me3SiCHN2, 9-diazofluorene and p-tolylN3, leading to the formation of the six-membered hydrazido complexes (η5-C5Me5)2Th[N(N=CHSiMe3)(C4Ph4)] (3) and (η5-C5Me5)2Th[N(N=C(C12H8))(C4Ph4)] (4) and the seven-membered bis(triazenido) complex (η5-C5Me5)2Th[N(N=N(p-tolyl))(C4Ph4)N(N=N(p-tolyl))] (5), respectively. [ABSTRACT FROM AUTHOR]

The reaction of the base-free terminal thorium imido complex [{η5-1,2,4-(Me3C)3C5H2}2ThN(p-tolyl)] ( 1) with p-azidotoluene yielded irreversibly the tetraazametallacyclopentene [{η5-1,2,4-(Me3C)3C5H2}2Th{N( p-tolyl)NNN( p-tolyl)}] ( 2), whereas the bridging imido complex [{[η5-1,2,4-(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 η2-diazenido iminato complex [{η5-1,2,4-(Me3C)3C5H2}2Th{η2-[NN(p-tolyl)]}{N(9-C13H8)}] ( 4) was formed. In contrast, the reaction of 1 with Me3SiCHN2 gave the nitrilimido complex [{η5-1,2,4-(Me3C)3C5H2}2Th{NH( p-tolyl)}{N2CSiMe3}] ( 5), which slowly converted into [{η5-1,2,4-(Me3C)3C5H2}{η5: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. [ABSTRACT FROM AUTHOR]

Reaction of [(cod)Pd(Me)(thf)][SbF6] or [(cod)Pd(Me)(MeCN)][B(ArF)4] (cod = 1,5-cyclooctadiene, B(ArF)4 = [3,5-(F3C)2C6H3]4B) with one or two equivalents of tBu3P gives [(tBu3P)2Pd(Me)]+ (3) exclusively. The two sterically encumbered tBu-groups prevent solvent coordination. In addition, this formally three coordinate complex is stabilized by a γ-agostic interaction in solid state, whereas solution NMR studies confirm that this interaction is rather weak. The strength of the γ-agostic interaction was evaluated using density functional theory (DFT) calculations. Surprisingly, [(tBu3P)2Pd(Me)]+ is unreactive toward CO, H2, C2H4 and norbornene. [ABSTRACT FROM AUTHOR]

The synthesis, electronic structure, and reactivity of a uranium metallacyclopropene were comprehensively studied. Addition of diphenylacetylene (PhC≡CPh) to the uranium phosphinidene metallocene [η5‐1,2,4‐(Me3C)3C5H2]2U=P‐2,4,6‐tBu3C6H2 (1) yields the stable uranium metallacyclopropene, [η5‐1,2,4‐(Me3C)3C5H2]2U[η2‐C2Ph2] (2). Based on density functional theory (DFT) results the 5f orbital contributions to the bonding within the metallacyclopropene U‐(η2‐C=C) moiety increases significantly compared to the related ThIV compound [η5‐1,2,4‐(Me3C)3C5H2]2Th[η2‐C2Ph2], which also results in more covalent bonds between the [η5‐1,2,4‐(Me3C)3C5H2]2U2+ and [η2‐C2Ph2]2− fragments. Although the thorium and uranium complexes are structurally closely related, different reaction patterns are therefore observed. For example, 2 reacts as a masked synthon for the low‐valent uranium(II) metallocene [η5‐1,2,4‐(Me3C)3C5H2]2UII when reacted with Ph2E2 (E=S, Se), alkynes and a variety of hetero‐unsaturated molecules such as imines, ketazine, bipy, nitriles, organic azides, and azo derivatives. In contrast, five‐membered metallaheterocycles are accessible when 2 is treated with isothiocyanate, aldehydes, and ketones. [ABSTRACT FROM AUTHOR]

A three-membered thorium metallaheterocycle [η5-1,3-(Me3C)2C5H3]2Th[η2-P2(2,4,6-iPr3C6H2)2] (4) is readily prepared besides H2 from [η5-1,3-(Me3C)2C5H3]2Th(PH-2,4,6-iPr3C6H2)2 (3) upon heating in toluene solution. Density functional theory (DFT) studies were performed to elucidate the 5f orbital contribution to the bonding within Th-(η2-P-P) revealing more covalent bonds between the [η5-1,3-(Me3C)2C5H3]2Th2+ and [η2-P2(2,4,6-iPr3C6H2)2]2− fragments than those in the related thorium metallacyclopropene. Consequently, distinctively different reactivity patterns emerge, e.g., while 4 reacts with pyridine derivatives such as 4-dimethyaminopyridnie (DMAP) and forms the DMAP adduct [η5-1,3-(Me3C)2C5H3]2Th[η2-P2(2,4,6-iPr3C6H2)2](DMAP) (5), it may also act as a [η5-1,3-(Me3C)2C5H3]2Th(II) synthon when reacted with bipy, Ph2S2 or Ph2Se2. Nevertheless, no reaction of complex 4 with alkynes is observed, but it reacts as a nucleophile towards nitriles and aldehydes resulting in five- or seven-membered metallaheterocycles, respectively. DFT computations provide some additional insights into the experimental observations. [ABSTRACT FROM AUTHOR]

Four- and five-coordinate high-spin ( S = 2) Fe(II) complexes bearing the pyrrolyl-derived t Bu PNP pincer ligand [ t Bu PNP = 2,5-( t Bu 2 PCH 2 ) 2 (C 4 H 2 N)] have been prepared. All three complexes were characterized by X-ray diffraction, zero-field 57 Fe Mössbauer spectroscopy and solid-state magnetic susceptibility studies. Furthermore, the experimentally determined Mössbauer parameters of compounds 4 – 6 can be modeled satisfactorily by density functional theory (DFT) computations at the B97D level of theory. Introduction of the sterically demanding bis(trimethylsilyl)amido moiety induces significant distortions from ideal tetrahedral geometry in [( t Bu PNP)FeN(SiMe 3 ) 2 ] ( 4 ), featuring an Fe(II) high-spin state with large negative axial zero-field splitting and slow paramagnetic relaxation at low temperature, as evidenced by measurements of the solid-state magnetic susceptibility and zero-field 57 Fe Mössbauer spectroscopy. Replacing the chlorido ligand in [( t Bu PNP)FeCl] ( 3 ) by the bidentate acetylacetonato (acac) ligand enforces a trigonal–bipyramidal structure in [( t Bu PNP)Fe(acac)] ( 5 ), in which the Fe(II) atom also adopts a high-spin configuration. Reaction of 3 with adamantyl azide allowed us to confirm the inherent lability of the phosphine coordination, since the azide inserts into the Fe P bond to form [( t Bu PNP N3Adamantyl )FeCl] ( 6 ), in which the t Bu PNP ligand is transformed to a phosphino-pyrrolyl-phosphazide ligand framework ( t Bu PNP N3Adamantyl ). This motif can be considered as a trapped Staudinger intermediate along the reaction pathway of free phosphines with organic azides to form phosphinimines. Bidentate binding of the phosphazide sidearm in κN:κN-fashion to the Fe(II) atom enforces an s - anti coordination of the P1–N2–N3–N4 moiety, which raises the barrier for the thermodynamically favorable N 2 elimination and allows this intermediate to be trapped. Complex 6 contains a high-spin Fe(II) atom with a square-pyramidal structure. [ABSTRACT FROM AUTHOR]

The synthesis, structure, and reactivity of an actinide metallacyclopropene were comprehensively studied. The reduction of [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1) with potassium graphite (KC8) in the presence of diphenylacetylene (PhC ≡ CPh) yields the first stable actinide metallacyclopropene [η5-1,2,4-(Me3C)3C5H2]2Th (η²-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--(η²-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 Th4+ shows unique reactivity patterns. [ABSTRACT FROM AUTHOR]