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A Cu-catalyzed asymmetric methylboration of 1,2-dihydroquinolines, 2H-chromenes and 2H-thiochromenes providing boryl products bearing two adjacent chiral centers with excellent selectivities, up to 99 : 1 dr and 99.9% ee, has been realized for the first time.

Enantioselective hydrogenation of α-trifluoromethylidene lactams catalyzed by the Rh/f-spiroPhos complex is first developed, providing an efficient approach for synthesis of various chiral trifluoroethyl lactams, with up to 99.9% ee and high turnover numbers (up to 10500).

A highly enantioselective Ni-catalyzed hydrogenation of β,β-disubstituted acrylic acids was first realized using Ph-BPE, providing straightforward access to chiral carboxylic acids in high yields with excellent enantioselectivities, up to 99% ee.

The manuscript describes a qualitative reactivity study on two uranium cumulene adducts. The derivative with the less bulky ligand is significantly more reactive than that with the bulkier ligand.

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-(Me3 C)3 C5 H2 ]2 U=P-2,4,6-tBu3 C6 H2 (1) yields the stable uranium metallacyclopropene, [η5 -1,2,4-(Me3 C)3 C5 H2 ]2 U[η2 -C2 Ph2 ] (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-(Me3 C)3 C5 H2 ]2 Th[η2 -C2 Ph2 ], which also results in more covalent bonds between the [η5 -1,2,4-(Me3 C)3 C5 H2 ]2 U2+ and [η2 -C2 Ph2 ]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-(Me3 C)3 C5 H2 ]2 UII when reacted with Ph2 E2 (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.

This paper describes the synthesis, structure, and reactivity of (η5-C5Me5)2U(═P-2,4,6-iPr3C6H2)(OPPh3) (2). Compound 2 can be accessed by a salt metathesis reaction of the uranium methyl chloride ...

This paper describes the synthesis and reactivity of [η5-1,3-(Me3Si)2C5H3]2U(P-2,4,6-iPr3C6H2)(OPMe3) (6) which is accessible from a ligand exchange reaction between [η5-1,3-(Me3Si)2C5H3]2U(P-2,4,6-iPr3C6H2)(OPPh3) (2) and Me3PO at ambient temperature. Phosphinidene 6 exhibits no reactivity towards internal alkynes, but readily reacts with various hetero-unsaturated molecules such as isothiocyanates, aldehydes, nitriles, isonitriles, and organic azides, forming uranium sulfido, oxido, imido, and uranaheterocyclic compounds. Nevertheless, with the bidentate ortho-dicyanobenzene o-C6H4(CN)2 the zwitterionic species [η5-1,3-(Me3Si)2C5H3]2U[NHC(N){C6H4CP(2,4,6-iPr3C6H2)CH2PMe2O}] (13) is isolated in good yield. Moreover, 6 converts with Ph2S2 to the uranium(III) phenylthiolate compound [η5-1,3-(Me3Si)2C5H3]2USPh(OPMe3) (7) in good isolated yield. Furthermore, the influence of the Lewis base on the reactivity of the uranium phosphinidene metallocenes has also been evaluated.

The Lewis base supported terminal uranium phosphinidene metallocene [η5-1,3-(Me3C)2C5H3]2U([double bond, length as m-dash]P-2,4,6-iPr3C6H2)(OPMe3) (2) could be isolated from a salt metathesis reaction in toluene at ambient temperature between [η5-1,3-(Me3C)2C5H3]2U(Cl)Me (1) and 2,4,6-iPr3C6H2PHK in the presence of Me3PO, and its structure and reactivity were probed in detail. No reaction of 2 with internal alkynes was observed, but it reacts in the presence of various heterounsaturated molecules such as CS2, isothiocyanates, aldehydes, imines, diazenes, carbodiimides, nitriles, isonitriles, diazoalkane, and organic azides, forming carbodithioates, sulfidos, oxidos, metallaheterocycles, and imido complexes, in good yields. Moreover, on reaction with the diazoalkane derivative Me3SiCHN2 the pseudophosphinimido uranium(iii) complex [η5-1,3-(Me3C)2C5H3]2U(N[double bond, length as m-dash]P-2,4,6-iPr3C6H2)(OPMe3) (20) can be isolated in good yield.

A highly efficient asymmetric hydrogenation of a series of γ-keto acid derivatives, including γ-keto acids, esters, and amides, using a Ni-(

The Lewis base stabilized uranium phosphinidene (η5-C5Me5)2U(═P-2,4,6-tBu3C6H2)(OPMe3) (2), which was derived from (η5-C5Me5)2U(Cl)Me (1) and 2,4,6-(Me3C)3C6H2PHK in toluene in the presence of Me3P...

A highly enantioselective hydrogenation of α,β-unsaturated boronate esters catalyzed by Rh-(S)-DTBM-Segphos complex has been developed. Both (Z)-α,β- and β,β-disubstituted substrates can be successfully hydrogenated to afford chiral boronates with excellent enantioselectivities, up to 98 % ee. Furthermore, the obtained chiral boronate esters, as important versatile synthetic intermediates are successfully transformed to the corresponding chiral alcohols, amines and other important derivatives with maintained enantioselectivities.

This paper describes the synthesis and reactivity of [η

A highly regioselective asymmetric hydroboration of 2 H-chromenes catalyzed by the complex of CuCl and diphosphine ligand ( S, R)-DuanPhos has been realized under mild conditions to produce 3-boryl chromans, achieving good yields and excellent enantioselectivities up to 96% ee. This work provides an efficient approach to the synthesis of chiral 3-boryl chromans and derivatives.

A highly efficient and enantioselective Rh-( R, R)-f-spiroPhos complex catalyzed hydrogenation of a series of unsaturated sulfones has been developed. With Rh-( R, R)-f-spiroPhos catalyst under mild conditions, not only the asymmetric hydrogenation of both the 3,3-diaryl and exocyclic α,β-unsaturated sulfones was first realized with up to 99.9% ee but also 3-alkyl-3-aryl and benzo[ b]thiophene-1,1-dioxides were successfully hydrogenated to the corresponding chiral sulfones with excellent enantioselectivities (up to 99.4% ee) regardless of the steric hindrance, electronic property, and geometry of the substrates. Moreover, this reaction offers a route to ( S)-(+)- ar-turmerone as a spice flavor, which is an important synthetic intermediate of pharmaceuticals.

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.

The stable base-free terminal phosphinidene thorium metallocene, [η5-1,2,4-(Me3C)3C5H2]2Th[double bond, length as m-dash]P-2,4,6-tBu3C6H2 (2), can be isolated from the reaction of the thorium dichloride complex [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1) with 2 equiv. of 2,4,6-(Me3C)3C6H2PHK in THF. The reactivity of 2 in the activation of various small organic molecules such as diselenides, phosphines, imines, ketones, phosphine oxides, thiazole, imidazole derivatives and amines was explored. For example, when complex 2 is treated with Ph2Se2, the phosphinidene is replaced, yielding diselenido compound [η5-1,2,4-(Me3C)3C5H2]2Th(SePh)2 (3). Moreover, E-H (E = P, N, C) bond activation occurs on exposure of 2 to 2,4,6-iPr3C6H2PH2, PhPH2, (p-tolyl)2C[double bond, length as m-dash]NH, 1-indanone, cyclohexanone, Me3PO, thiazole, 1-methylimidazole and p-toluidine, resulting in the phosphido complex [η5-1,2,4-(Me3C)3C5H2][η5,κ-C-1,2-(Me3C)2-4-(CH2CMe2)C5H2]Th(PH-2,4,6-iPr3C6H2) (4), the metallaheterocycle [η5-1,2,4-(Me3C)3C5H2]2Th(η2-P2Ph2) (5), the iminato phosphido complex [η5-1,2,4-(Me3C)3C5H2]2Th(PH-2,4,6-tBu3C6H2)[N[double bond, length as m-dash]C(p-tolyl)2] (6), the phosphido enolyl compound [η5-1,2,4-(Me3C)3C5H2]2Th(PH-2,4,6-tBu3C6H2)(κ-O-1-OC9H7) (7), the enolyl complex [η5-1,2,4-(Me3C)3C5H2][η5,κ-C-1,2-(Me3C)2-4-(CH2CMe2)C5H2]Th(κ-O-1-OC6H9) (8), the alkyl complex [η5-1,2,4-(Me3C)3C5H2][η5,κ-C-1,2-(Me3C)2-4-(CH2CMe2)C5H2]Th(κ-O,C-OPMe2CH2) (9), the phosphido thiazolyl complex [η5-1,2,4-(Me3C)3C5H2]2Th(PH-2,4,6-tBu3C6H2)(C3H2NS) (10), the bis-imidazolyl complex [η5-1,2,4-(Me3C)3C5H2]2Th[2-(1-MeC3H2N2)]2 (11), and the imido complex [η5-1,2,4-(Me3C)3C5H2]2Th[double bond, length as m-dash]N(p-tolyl) (12), respectively. Several spectroscopic techniques were employed for the characterisation of the new complexes 3-11, and in addition the solid-state molecular structures of compounds 3-6, 8-9 and 11 were further confirmed by X-ray diffraction analyses.

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.

The Lewis base supported terminal uranium phosphinidene metallocene [η5-1,3-(Me3C)2C5H3]2U([double bond, length as m-dash]P-2,4,6-iPr3C6H2)(OPMe3) (2) could be isolated from a salt metathesis reaction in toluene at ambient temperature between [η5-1,3-(Me3C)2C5H3]2U(Cl)Me (1) and 2,4,6-iPr3C6H2PHK in the presence of Me3PO, and its structure and reactivity were probed in detail. No reaction of 2 with internal alkynes was observed, but it reacts in the presence of various heterounsaturated molecules such as CS2, isothiocyanates, aldehydes, imines, diazenes, carbodiimides, nitriles, isonitriles, diazoalkane, and organic azides, forming carbodithioates, sulfidos, oxidos, metallaheterocycles, and imido complexes, in good yields. Moreover, on reaction with the diazoalkane derivative Me3SiCHN2 the pseudophosphinimido uranium(iii) complex [η5-1,3-(Me3C)2C5H3]2U(N[double bond, length as m-dash]P-2,4,6-iPr3C6H2)(OPMe3) (20) can be isolated in good yield.

The synthesis, electronic structure, and reactivity of a uranium metallacyclopropene were comprehensively studied. Addition of diphenylacetylene (PhC≡CPh) to the uranium phosphinidene metallocene [η 5‐1,2,4‐(Me3C)3C5H2]2U=P‐2,4,6‐tBu3C6H2 (1) yields the stable uranium metallacyclopropene, [η 5‐1,2,4‐(Me3C)3C5H2]2U[η 2‐C2Ph2] (2). Based on density functional theory (DFT) results the 5f orbital contributions to the bonding within the metallacyclopropene U‐(η 2‐C=C) moiety increases significantly compared to the related ThIV compound [η 5‐1,2,4‐(Me3C)3C5H2]2Th[η 2‐C2Ph2], which also results in more covalent bonds between the [η 5‐1,2,4‐(Me3C)3C5H2]2U2+ and [η 2‐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 [η 5‐1,2,4‐(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., The intrinsic reactivity of a stable uranium metallacyclopropene complex, [η 5‐1,2,4‐(Me3C)3C5H2]2U(η 2‐C2Ph2), was evaluated and compared to that of other uranium and thorium metallacyclopropenes. Although structurally similar, the thorium and uranium metallacyclopropenes exhibit distinctively different reactivity.

A Lewis base supported terminal uranium phosphinidene, [η5-1,3-(Me3C)2C5H3]2U(═P-2,4,6-tBu3C6H2)(OPMe3) (5), is isolated from the reaction of the uranium methyl chloride [η5-1,3-(Me3C)2C5H3]2U(Cl)M...

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’’’=η 5‐1,2,4‐(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., The first base‐free terminal uranium phosphinidene metallocene was prepared and it showed a distinctively different reactivity compared to the related thorium phosphinidenes.

The synthesis, structure, and reactivity of a base-free terminal actinide phosphinidene metallocene have been comprehensively studied. The salt metathesis reaction of the thorium methyl iodide complex Cp‴2Th(I)Me (2; Cp‴ = η5-1,2,4-(Me3C)3C5H2) with Mes*PHK (Mes* = 2,4,6-(Me3C)3C6H2) in THF furnishes the first stable base-free terminal phosphinidene actinide metallocene, Cp‴2Th═PMes* (3). Density functional theory (DFT) shows that the bonds between the Cp‴2Th2+ and [PMes*]2- fragments are more covalent than those in the related thorium imido complex. While the phosphinidene complex 3 shows no reactivity toward alkynes, it reacts with a variety of heterounsaturated molecules such as CS2, isothiocyanate, nitriles, isonitriles, and organic azides, forming carbodithioates, imido complexes, metallaaziridines, and azido compounds. These experimental observations are complemented by DFT computations.

The Lewis base supported thorium terminal imido metallocene (η5-C5Me5)2Th═N(mesityl)(DMAP) (1) reacts with various small organic molecules such as thiazoles, silanes, internal acetylenes, nitriles, ketones, CS2, isothiocyanates, carbodiimides, lactides, organic azides, and diazoalkane derivatives. For example, while 1 forms the adduct (η5-C5Me5)2Th═N(mesityl)(OPPh3) (2) with Ph3PO, deprotonation occurs between 1 and thiazole to give the amido thiazolyl complex (η5-C5Me5)2Th(NHmesityl)(C3H2NS) (3). Moreover, the five-membered metallaheterocycle (η5-C5Me5)2Th[κ2-N,C-{N(2-CH2-4,6-Me2C6H2)(SiH2Ph)}](DMAP) (4) is isolated from a mixture of 1 and PhSiH3. In addition, treatment of 1 with PhCN, Ph2CHCN, or Me3SiCN gives the zwitterionic complex (η5-C5Me5)2Th[κ-N-{NCPh(N(mesityl))}](DMAP) (5), and iminato compounds (η5-C5Me5)2Th[N(mesityl)C(CHPh2)NH](N═C═CPh2) (6) and (η5-C5Me5)2Th[2-{N═C(SiMe3)}-4-Me2NC5H3N](NC) (7), respectively. Furthermore, reaction of 1 with PhC≡CMe and Me3SiC≡CC≡CSiMe3 afford the amido pyrid...

Addition of potassium graphite (KC8) to a solution of (η5-C5Me5)2UCl2 (1) and 2,2′-bipyridine (bipy) gives the uranium bipyridyl metallocene (η5-C5Me5)2U(bipy) (2) in good yield. In complex 2 a bipy radical anion is coordinated to a U(III) atom, and it is therefore an ideal starting material for small-molecule activation: e.g., it serves as a synthetic equivalent for the (η5-C5Me5)2UII fragment on treatment with conjugated alkynes and a variety of heterounsaturated molecules such as imines, carbodiimide, organic azides, hydrazine, and azo derivatives. Alternatively, it may also react with aldehydes, ketones, nitriles, and α,β-unsaturated reagents such as p-ClPhCHO, (CH2)5CO, PhCN, and methyl methacrylate (MMA), forming the C–C bond coupling products (η5-C5Me5)2U[(bipy)(p-ClPhCHO)] (10), (η5-C5Me5)2U[(bipy){(CH2)5CO}] (11), (η5-C5Me5)2U[(bipy)(PhCN)] (12), (η5-C5Me5)2U[(bipy){CH2═C(Me)CO(OMe)] (13a), and [(η5-C5Me5)2U{OC(OMe)═C(Me)CH2–3-bipy}]2 (13b), respectively, in quantitative conversion. Furthermore, ...

The synthesis, electronic structure, and reactivity of a uranium metallacyclocumulene were studied. Reduction of [(η5-C5Me5)2UCl2] (1) with potassium graphite (KC8) in the presence of 1,4-bis(trimethylsilyl)butadiyne (Me3SiC≡C–C≡CSiMe3) forms the uranium metallacyclocumulene [(η5-C5Me5)2U{η4-C4(SiMe3)2}] (2) in good yield. Magnetic susceptibility data confirm that 2 behaves as a U(IV) complex, and density functional theory (DFT) studies indicate a substantial 5f orbital contribution to the bonding of the metallacyclopentatriene U(η4-C═C═C═C) moiety, leading to more covalent bonds between the [(η5-C5Me5)2U]2+ and [η4-C4(SiMe3)2]2– fragments than those found in the related Th(IV) compound. Consequently, very different reactivity patterns emerge; e.g., 2 can act as a synthetic equivalent for the (η5-C5Me5)2U(II) fragment when reacted with conjugated species such as butadiyne, bipy, and diazabutadiene derivatives. Alternatively, the [(η4-Me3SiC═C═C═CSiMe3)]2– moiety in 2 may react as a nucleophile when expose...

A highly efficient kinetic resolution of racemic 2-substituted 1,2-dihydroquinolines via asymmetric Cu-catalyzed borylation has been realized for the first time. Under mild conditions, a variety of chiral 3-boryl-1,2,3,4-tetrahydroquinolines containing two vicinal stereogenic centers as well as the recovered 2-substituted 1,2-dihydroquinolines were afforded after 30 minutes in high yields with up to 99% ee (dr > 99 : 1) and over 98% ee values, respectively, corresponding to kinetic selectivity factors of up to 569. Moreover, this protocol was successfully applied to the asymmetric synthesis of a selective estrogen receptor modulator.

The uranium metallacyclocumulene, [η5-1,3-(Me3C)2C5H3]2U(η4-C4Ph2) (2) was isolated by the reduction of [η5-1,3-(Me3C)2C5H3]2UCl2 (1) with potassium graphite (KC8) in the presence of 1,4-diphenylbutadiyne (PhCC–CCPh) in good yield. Furthermore it was fully characterized including the determination of its molecular structure; and the reactivity of 2 towards various small unsaturated organic molecules was explored. For example, while complex 2 shows no reactivity with alkynes and 2,2′-bipyridine (bipy), it reacts as a nucleophile when exposed to carbodiimides, diazabutadienes, isothiocyanates, ketones, and pyridine derivatives, leading to five-, seven- or nine-membered heterometallacycles. In contrast, treatment of complex 2 with CS2 results in CS bond cleavage and forms the binuclear complex [η5-1,3-(Me3C)2C5H3]2U[μ-η4:η3-PhCCC(S)C(Ph)CS]U[η5-1,3-(Me3C)2C5H3]2 (10). Density functional theory (DFT) studies complement the experimental study.

A highly efficient enantioselective hydrogenation of 1,2-dicyanoalkenes catalyzed by the complex of rhodium and f-spiroPhos has been developed. A series of 1,2-dicyanoalkenes were successfully hydrogenated to the corresponding chiral 1,2-dicyanoalkanes under mild conditions with excellent enantioselectivities (up to 98% ee). This methodology provides efficient access to the asymmetric synthesis of chiral diamines.

A Cu-catalyzed regio- and enantioselective hydroboration of various naphthylallylic compounds affording chiral boronates with high yields and excellent enantioselectivities (up to 96% ee) was presented. The utility of the boronated products is further illustrated by other stereospecific C-B bond transformations to produce amino alcohols and other useful compounds.

The salt metathesis reaction of the thorium methyl chloride complex [η5-1,3-(Me3C)2C5H3]2Th(Cl)Me (3) with 2,4,6-(Me3C)3C6H2PHK in benzene furnishes an alkali-metal halide-bridged phosphinidiide actinide metallocene, {[η5-1,3-(Me3C)2C5H3]2Th(═P-2,4,6-tBu3C6H2)(ClK)}2 (4), whose structure and reactivity was investigated in detail. On the basis of density functional theory (DFT) studies, the 5f orbitals in the model complex [η5-1,3-(Me3C)2C5H3]2Th(═P-2,4,6-tBu3C6H2) (4′) contribute significantly to the bonding of the phosphinidene Th═P(2,4,6-tBu3C6H2) moiety. Furthermore, compared to the related thorium imido complex, the bonds between the [η5-1,3-(Me3C)3C5H2]2Th2+ and [P-2,4,6-tBu3C6H2]2– fragments are more covalent. The reactivity of compound 4 toward alkynes and a variety of heterounsaturated molecules such as nitriles, isonitriles, carbodiimides, imines, isothiocyanates, aldehydes, ketones, thiazoles, quinolines, organic azides, pyridines, and imidazoles, forming metallacycles, phospholes, imidos, metal...

The formation of actinide-transition metal heterobimetallics mediated by a terminal actinide imido complex was comprehensively studied. The reaction of the thorium imido complex [(η5 -C5 Me5 )2 Th=N(mesityl)(DMAP)] (3), prepared from [(η5 -C5 Me5 )2 ThMe2 ] (1) and mesitylNH2 or [(η5 -C5 Me5 )2 Th(NHmesityl)2 ] (2) in the presence of 4-(dimethylamino)pyridine (DMAP), with copper(I) halides gave the first thorium-copper heterobimetallic compounds [(η5 -C5 Me5 )2 Th(X){N(mesityl)Cu(DMAP)}] (X=Cl (4), Br (5), I (6)). Complexes 4-6 feature an unusual geometry with a short Th-Cu distance, which DFT studies attribute to a weak donor-acceptor bond from the Cu+ atom to the electropositive Th4+ atom. They are reactive species, as was shown by their reaction with the dimethyl complex [(η5 -C5 Me5 )2 ThMe2 ] (1). Furthermore, a comparison between Th and early transition metals confirmed that Th4+ exhibits distinctively different reactivity from d-transition metals.

Reduction of (η5-C5Me5)2ThCl2 (1) with potassium graphite (KC8) in the presence of 2,2′-bipyridine forms the thorium bipy metallocene (η5-C5Me5)2Th(bipy) (2) in good yield. Complex 2 was fully characterized and reacts with various small molecules. For example, 2 serves as a source for the (η5-C5Me5)2Th(II) fragment when exposed to conjugated alkynes, elemental sulfur and their organic derivatives, diazabutadiene, carbodiimide, CS2, isothiocyanate, and organic azides. Furthermore, treatment of 2 with ketone Ph2CO, thio-ketone Ph2CS, imine PhCH═NPh, and nitrile PhCN results in C–C bond coupling products (η5-C5Me5)2Th[(bipy)(Ph2CO)] (10), (η5-C5Me5)2Th[(bipy)(Ph2CS)] (11), (η5-C5Me5)2Th[(bipy)(PhCHNPh)] (12), and (η5-C5Me5)2Th[(bipy)(PhCN)] (13), respectively, in quantitative conversion.

An additive-free enantioselective hydrogenation of β,β-disubstituted unsaturated carboxylic acids catalyzed by the Rh-(R,R)-f-spiroPhos complex has been developed. Under mild conditions, a wide scope of β,β-disubstituted unsaturated carboxylic acids were hydrogenated to the corresponding chiral carboxylic acids with excellent enantioselectivities (up to 99.3% ee). This methodology was also successfully applied to the synthesis of the pharmaceutical molecule indatraline.

The formation of thorium metallacyclopentadiene and metallacyclopropene complexes is significantly influenced by the steric and electronic properties of the internal alkyne employed during their syntheses. The reduction of (η5-C5Me5)2ThCl2 (2) with potassium graphite (KC8) or lithium in the presence of internal phenyl(alkyl)acetylenes (PhC≡CR) selectively yields the corresponding Cs-symmetric thorium metallacyclopentadienes (η5-C5Me5)2Th[η2-C(Ph)═C(R)C(Ph)═C(R)] (R = Me (4), iPr (5), C6H11 (6)), while the phenyl(silyl)acetylene PhC≡CSiHMe2 gives the C2v-symmetric metallacyclopentadiene (η5-C5Me5)2Th[η2-C(SiHMe2)═C(Ph)C(Ph)═C(SiHMe2)] (7). However, the sterically more encumbered acetylene derivative PhC≡CSiMe3 affords the chloro metallacyclopropene complex [(η5-C5Me5)2Th(η2-C2Ph(SiMe3))(Cl)][Li(EDM)2] (8), whereas Me3SiC≡CSiMe3 forms the chloro alkenyl complex [(η5-C5Me5)2Th[C(SiMe3)═CHSiMe3](Cl) (9), in which the chloro metallacyclopropene intermolecularly activates a C–H bond of the solvent (C7H8). Densi...

The uranium metallacyclopropene (η5-C5Me5)2U[η2-C2(SiMe3)2] (1) reacts with various small unsaturated organic molecules. For example, replacement of bis(trimethylsilyl)acetylene occurs when complex 1 is exposed to alkynes, conjugated alkenes, nitriles and quinones. Reaction of 1 with internal phenyl(alkyl)acetylene PhCCMe selectively yields the Cs symmetric uranium metallacyclopentadiene (η5-C5Me5)2U[η2-C(Ph)C(Me)–C(Ph)C(Me)] (6) after the loss of bis(trimethylsilyl)acetylene, while treatment of 1 with phenyl(silyl)acetylenes (PhCCR, R = SiHMe2, SiMe3) gives the corresponding C2v symmetric isomers (η5-C5Me5)2U[η2-C(R)C(Ph)–C(Ph)C(R)] (R = SiHMe2 (7), SiMe3 (8)). Furthermore, while no deprotonation occurs between complex 1 and pyridine derivatives, cyclohexanone can be inserted into the uranium metallacyclopropene moiety of 1 to yield the five-membered, heterocyclic complex (η5-C5Me5)2U[OC(CH2)5(C2(SiMe3)2)] (14) in quantitative conversion. Density functional theory (DFT) studies have been performed to complement the experimental studies.

A highly efficient, iridium-catalyzed, enantioselective hydrogenation of β,β-disubstituted nitroalkenes has been developed. Using a complex consisting of iridium and (S,S)-f-spiroPhos as the catalyst, a variety of β,β-disubstituted nitroalkenes were successfully hydrogenated to the corresponding chiral nitroalkanes with excellent enantioselectivities (up to 98% ee) and high turnover numbers (TON=1000).

All-carbon metallacycles of the d-transition metals have received widespread attention over the past three decades because of their exceptional intrinsic reactivity. However, in recent years, significant progress has also been made in the synthesis and characterization of actinide metallacyclopropenes, metallacyclopentadienes, and metallacyclocumulenes (metallacyclopentatrienes). Such actinide metallacycles are of interest because of their unique structural properties, their potential application in novel group transfer reactions and catalysis, as well as their ability to engage the 5f orbitals in metal–ligand bonding. This short review summarizes the latest developments in this area focusing on all-carbon actinide metallacycles, i.e., metallacyclopropenes, metallacyclopentadienes, and metallacyclocumulenes (metallacyclopentatrienes).

A Cu-catalyzed regio- and enantioselective hydroboration of 1,2-dihydroquinolines with high yields and excellent enantioselectivities (up to 98% ee) was presented. This method could be applied in the asymmetric synthesis of the important intermediates used in the enantioselective synthesis of the potential agent Sumanirole for the treatment of Parkinson’s disease and of the potentially interesting positive inotropic agent (S)-903.

Reduction of (η5-C5Me5)2ThCl2 (1) with potassium graphite (KC8) in the presence of 1,4-diphenylbutadiyne (PhC≡CC≡CPh) yields the first actinide metallacyclocumulene, the thorium metallacyclopentatriene (η5-C5Me5)2Th(η4-C4Ph2) (2). The structure and reactivity of 2 were investigated in detail; structural parameters and density functional theory (DFT) studies confirm the presence of a metallacyclopentatriene unit in 2. Furthermore, DFT computations also indicate a notable contribution of the 5f orbitals to the bonding of the metallacyclopentatriene Th–(η4-C═C═C═C) moiety. While complex 2 shows no reactivity toward alkynes, it reacts with a variety of heterounsaturated molecules such as isothiocyanates, carbodiimides, aldehydes, ketones, nitriles, pyridines, and diazoalkane derivatives. DFT studies complement the experimental observations and provide additional insights. Furthermore, in comparison to group 4 metals, the thorium metallacyclopentatriene 2 exhibits distinctively different reactivity patterns.

A highly efficient enantioselective hydrogenation of α,β-unsaturated nitriles catalyzed by Rh-(R,R)-f-spiroPhos complex has been developed. With Rh-(R,R)-f-spiroPhos catalyst and under mild conditions, a wide range of α,β-unsaturated nitriles including the (E)- and (Z)-isomers of 3-alkyl-3-aryl, 3,3-diaryl, and 3,3-dialkyl α,β-unsaturated nitriles were hydrogenated to the corresponding chiral nitriles with excellent enantioselectivities (up to 99.9% ee) and high turnover numbers (TON up to 10,000).

The synthesis, structure, and reactivity of a thorium metallacyclopentadiene were comprehensively studied. The reduction of (η(5)-C5Me5)2ThCl2 () with potassium graphite (KC8) in the presence of diphenylacetylene (PhC[triple bond, length as m-dash]CPh) yields the first thorium metallacyclopentadiene complex (η(5)-C5Me5)2Th(η(2)-C4Ph4) (). Density functional theory (DFT) studies suggest that the 5f orbitals are involved in the bonding of the metallacyclopentadiene Th-(η(2)-C[double bond, length as m-dash]C-C[double bond, length as m-dash]C) moiety. Compared to the thorium metallacyclopropene, complex 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 (η(5)-C5Me5)2Th[N(N[double bond, length as m-dash]CHSiMe3)(C4Ph4)] () and (η(5)-C5Me5)2Th[N(N[double bond, length as m-dash]C(C12H8))(C4Ph4)] () and the seven-membered bis(triazenido) complex (η(5)-C5Me5)2Th[N(N[double bond, length as m-dash]N(p-tolyl))(C4Ph4)N(N[double bond, length as m-dash]N(p-tolyl))] (), respectively.

The synthesis of C2 symmetric enantiomerically pure open Ca and Sr metallocenes, [(η(5)-pdl*)2Ca(thf)] (1) and [(η(5)-pdl*)2Sr(thf)2] (2) (pdl* = dimethylnopadienyl) is described and these complexes were fully characterized. The solid state structures confirm that the pdl* ligands coordinate exclusively with the less sterically demanding site to the Ca and Sr atoms. These complexes are active catalysts for the controlled ring opening polymerization (ROP) of rac-lactide to give heterotactically enriched polylactides (PL) with narrow polydispersities (PDI = 1.29-1.31) and without adding further activators.

Inter- and intramolecular C–H bond activations by thorium metallacyclopropene complexes were comprehensively studied. The reduction of [η5-1,2,4-(Me3C)3C5H2]2ThCl2 (1) with potassium graphite (KC8) in the presence of internal alkynes (PhCCR) yields the corresponding thorium metallacyclopropenes [η5-1,2,4-(Me3C)3C5H2]2Th(η2-C2Ph(R)) (R = Ph (2), Me (3), iPr (4), C6H11 (5)). Complexes 3–5 derived from phenyl(alkyl)acetylenes are very reactive resulting in an intramolecular C–H bond activation of the 1,2,4-(Me3C)3C5H2 ligand. In contrast, no intramolecular C–H bond activation is observed for the diphenylacetylene derived complex 2, but it does activate α-C–H bonds in pyridine or carbonyl derivatives upon coordination. Density functional theory (DFT) studies complement the experimental studies and provide additional insights into the observed reactivity.