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International audience; An investigation of the formation of a thorium phosphinidiide reveals that changing from a 2,4,6-(Pr3C6H2)-Pr-i (Tipp)-substituted phosphido ligand to a 2,4,6-Me3C6H2 (Mes) ligand forms a similar product, [(C5Me5)(2)Th](2)(P-2,6-CH2C6H2-4-CH3), but via a different sequence of bond activations. The resulting phosphinidiide was reacted with 1 and 2 equiv of (BuCN)-Bu-t, leading to mono(ketimide), [(C5Me5)(2)Th](2)[mu(2)-P-(2-CH2-6-(N=C(Bu-t)(CH2))-4-Me-C6H2)], and bis(ketimide), [(C5Me5)(2)Th](2)[mu(2)-P-(2-CH2-6-(N=C(Bu-t)(CH2))-4-Me-C6H2)], complexes, respectively, through insertion into the thorium- carbon bonds. An analysis of the Th-P-Th moiety showed a correlation of decreased Th-P-Th bond angle and upheld P-31 NMR chemical shift with decreasing Th-P covalent bond character.

International audience; Treatment of the U(III) complex, [(C5Me5)(2)U(OMes)(THF)], Mes = 2,4,6-Me3C6H2, with Fe(CO)(5) forms [{(C5Me5)(2)(MesO)U}(2)(mu(2)-(OC)(2)Fe(CO)(2))] with the bridging, tetrahedral Fe(CO)(4) moiety. This complex has been studied using H-1 NMR, IR vibrational, UV-vis electronic absorption, and zero-field Fe-57 Mossbauer spectroscopy as well as single-crystal X-ray diffraction analysis, magnetic measurements, and DFT calculations.

A study of the comparative reactivity of CO, CO2, tBuCN, and tBuNC with (C5Me5)2An[P(H)Mes]2 (An = Th, U) has been undertaken. While CO2 and tBuNC form identical products with both metals, namely (...

The base-free divalent samarium complex Cptt2Sm (1; Cptt = 1,3-(tBu)2(C5H3)) has been synthesized in diethyl ether by salt metathesis of SmI2. Crystals of 1 suitable for X-ray study have been obtained by sublimation at 116 °C under reduced pressure. The dissolution of 1 in thf and pyridine solution leads to the solvent adducts Cptt2Sm(thf)2 (3) and Cptt2Sm(py) (4), respectively, while drying 3 under reduced pressure yields CpttSm(thf) (5). The reaction of CO2 with the base-free divalent samarium complexes Cptt2Sm (1) and Cpttt2Sm (2; Cpttt =1,2,4-(tBu)3(C5H2)) leads to the clean formation of bridged carbonate samarium dimers [Cpttt2Sm]2(μ-CO3) (7) and [Cptt2Sm]2(μ-CO3) (8). This is indicative of the reductive disproportionation of CO2 in both cases with release of CO. This contrasts with the formation of the oxalate-bridged samarium dimer reported from the reaction of CO2 with the Cp*2Sm(thf)2 complex. Otherwise, the reaction with CO does not proceed with the bulky complexes, while traces of O2 have led t...

Reaction of the trivalent uranium complex [((Ad,MeArO)3N)U(DME)] with [Na(OCP)(dioxane)2.5] and 2.2.2-crypt yields the μ-oxo-bridged, diuranium complex [Na(2.2.2-crypt)][{((Ad,MeArO)3N)U(DME)}(μ-O){((Ad,MeArO)3N)U(CP)}] (1). Complex 1 features an asymmetric, dinuclear UIV–O–UIV core structure with a cyaphide (CP–) anion η1-CP bound to one of the U ions, and a κ2-O DME coordinated to the other. The CP– ligand is unprecedented in uranium chemistry and is formed through reductive C–O bond cleavage of the phosphaethynolate anion (OCP–). An analogous reaction was performed starting from the tetravalent uranium halide complex [((Ad,MeArO)3N)U(DME)(Cl)]. This salt metathesis approach with [Na(OCP)(dioxane)2.5] results in formation of the mononuclear complex [((Ad,MeArO)3N)U(DME)(OCP)] (2) with an OCP– anion bound to the uranium(IV) center via the oxygen atom in an η1-OCP fashion.

A new type of synthesis, referred to as oxidative methylation, is developed for [Cp*2Yb]2(μ-X) and [Cp*2Yb]2(μ-X)(X), where X = Me, using MeCu or Cp*2VMe as the methyl transfer reagent and Cp*2Yb. The synthetic methodology is extended to other X derivatives such as the halides and BH4. Reaction of [Cp*2Yb]2(μ-Me)(Me) and H2 yields the mixed-valent hydride [Cp*2Yb]2(μ-H), which eliminates H2 on gentle heating, forming Cp*2Yb. When Cp*2VX is replaced by Cp*2TiX, 1:1 adducts based upon Ti(III,d1) are isolated. The X-ray crystal structure of [Cp*2Yb](μ-Me)[TiCp*2] shows that the methyl group bridges the two different decamethylmetallocene fragments in a near-linear fashion, a geometry that is likely to resemble the transition state of the single-electron-transfer precursor complex. A CASSCF computational study on the mixed-valent hydride [Cp*2Yb]2(μ-H) shows that the ground state is a spin doublet in which the hydride forms a symmetric bridge to both Yb atoms. The three spins forming the ground-state doublet ...

Two synthetic approaches to the new three-decker Yb(II) complex [CpBn5Yb(DME)]2[μ-C10H8] (1) were successfully employed: the reaction of [CpBn5Yb(DME)(μ-I)]2 (2) with 2 molar equiv of [C10H8]−·K in DME and the reaction of [YbI(DME)2]2[μ-C10H8] (3) with CpBn5K in a 1:2 molar ratio in DME. Complex 1 was proved to be a Yb(II) binuclear triple-decker complex containing a dianionic naphthalene ligand bridging two CpBn5Yb(DME) fragments in a μ-η4:η4 fashion. An oxidative substitution of (C10H8)2– by trans-(1E,3E)-1,4-diphenylbuta-1,3-diene afforded the three-decker Yb(II) complex [CpBn5Yb(DME)]2(μ-η4:η4 -PhCHCHCHCHPh) (4) with a dianionic μ-η4:η4-bridging diphenylbutadiene ligand and naphthalene. The reaction of 1 with excess P4 also occurs with oxidation of (C10H8)2–, whereas Yb remains divalent. The reaction results in the formation of the trinuclear Yb(II) complex with a μ-bridging P73– ligand [CpBn5Yb(DME)]3(P7) (5). Protonation of the Yb–C10H8 bond in 1 with PhPH2 (1:2 molar ratio) afforded the dimeric pho...

Monocationic bis(hydrocarbyl)yttrium complexes [YR2(THF)2][A] (R = CH2SiMe3, CH2C6H4-o-NMe2; A = weakly coordinating anion) underwent hydrogenolysis using dihydrogen or phenylsilane to give a mixture of polynuclear solvent-stabilized dihydride cations [YH2(THF)2]n[A]n. The mixture composition as well as the nuclearity n depended on the starting material, solvent, and reaction conditions. NMR spectroscopic data in solution and X-ray diffraction data suggested that the main product was tetranuclear, although conclusive structural data were not obtained. DFT calculations supported a closo-type tetrahedral [YH2(THF)2]44+ core. The hydridic character of these cations was revealed by their reaction with benzophenone to give the bis(diphenylmethoxy) cation [Y(OCHPh2)2(THF)4][AlR4]. The reaction of this cluster with the (NNNN)-type macrocycle Me4TACD under dihydrogen gave the dinuclear tetrahydride dication with quadruply bridging hydride ligands, [Y2(μ-H)4(Me4TACD)2][A]2, analogous to the previously characterized lutetium derivative. NH-acidic (Me3TACD)H gave the dinuclear dihydride dication [Y2(μ-H)2(Me3TACD)2(THF)2][A]2.

Coordination of the triphosphine–fluorosilane [o-(iPr2P)C6H4]3SiF to AuCl results in the formation of a trigonal pyramidal cationic complex. Though cationic, the gold center acts as a Lewis base and is engaged in significant Au→Si interaction, as substantiated by X-ray diffraction and NMR spectroscopy. In solution, the P,P,P,Si tetracoordinate cationic complex coexists with a neutral P,P,Cl tricoordinate form, with a pendant phosphine buttress and without Au→Si interaction. The bonding situation in the two isomeric forms has been assessed by DFT calculations. Coordination of the third phosphine arm is shown to induce cationization and to play a key role in the presence of the Au→Si interaction.

Introduction of four tBu groups into a carbazol-yl framework leads to switching of the metal–ligand bonding in the Ln(II) and Ca complexes from σ to π. Complexes [(tBu4Carb)2Ln] (Ln = Sm, Eu, Yb, Ca) are amido analogues of metallocenes, which adopt the sandwich structures with parallel disposition of the aromatic ligands and strong contribution of η3-mode into η5 metal–ligand bonding. The DFT calculations demonstrated that the geometry is due to steric effects (presence of the bulky tBu groups) as well as the maximization of the overlap between the Sm 4f orbital and the π-type nitrogen lone pair of the carbazol-yl ligand. Coordination of DME to the metal centers in [(tBu4Carb)2M] (M = Sm, Yb) results in the heterolytic dissociation of the metal–ligand π-bond and the formation of ionic complexes [tBu4Carb–]2[Ln2+(DME)n].

International audience; The scandium complex bearing both methylidene and phosphinidene ligands, [(LSc) 2 (μ 2-CH 2)(μ 2-PDIPP)] (L = [MeC(NDIPP)CHC(NDIPP)Me] − , DIPP = 2,6-(i Pr) 2 C 6 H 3) (2), has been synthesized, and its reactivity has been investigated. Reaction of scandium methyl phosphide [LSc(Me){P(H)DIPP}] with 1 equiv of scandium dimethyl complex [LScMe 2 ] in toluene at 60 °C provided complex 2 in good yield, and the structure of complex 2 was determined by single-crystal X-ray diffraction. Complex 2 easily undergoes nucleophilic addition reactions with CO 2 , CS 2 , benzonitrile, and tert-butyl isocyanide. In the above reactions, the unsaturated substrates insert into the Sc−C(methylidene) bond to give some interesting dianionic ligands while the Sc−P(phosphinidene) bond remains untouched. The bonding situation of complex 2 was analyzed using DFT methods, indicating a more covalent bond between the scandium ion and the phosphinidene ligand than between the scandium ion and the methylidene ligand. ■ INTRODUCTION Alkylidene (or carbene) and phosphinidene complexes of transition metals have attracted intense interest and been extensively studied in the past decades. 1,2 The research on such complexes has revealed rich reactivity and applications in group-transfer and catalytic reactions. One exception is those complexes with rare-earth metal (Sc, Y, and lanthanide metal) ions. Rare-earth metal ions are among the hardest Lewis acids, whereas alkylidene and phosphinidene ligands are soft Lewis bases; thus, the rare-earth metal−alkylidene (or phosphini-dene) coordination is mismatched based on the Pearson's HSAB principle. 3 Up to now, the rare-earth metal alkylidene and phosphinidene complexes remain limited. 4−6 The reactivity study showed that most of the rare-earth metal alkylidene and phosphinidene complexes can react as the alkylidene or phosphinidene transfer agents with ketones to give alkenes or phosphaalkenes. 4 It was also found that some of the rare-earth metal alkylidene and phosphinidene complexes undergo nucleophilic addition reactions with unsaturated substrates, such as CO, isocyanate, carbodiimide, and isocyanide. 5k,l,6f,g We have developed a type of β-diketiminato based tridentate ligands, which can stabilize a series of rare-earth metal dialkyl complexes, 7 and a scandium terminal imido complex. 8 Recently, we obtained a scandium bridged phosphinidene complex [{MeC(NDIPP)CHC(Me)NCH 2 CH 2 N(i Pr) 2 }Sc{μ-PC 6 H 3-(2,6-Me 2)}] 2 (DIPP = 2,6-(i Pr) 2 C 6 H 3)), in which the pendant arm of the tridentate ligand is not coordinated to the scandium ion due to the phosphinidene ligand having a strong tendency to bridge two or more rare-earth metal centers. 6f Thus, we carried out a study to synthesize a scandium phosphinidene complex supported by the bulky β-diketiminato ligand, [MeC(NDIPP)CHC(NDIPP)Me] − (DIPP = 2,6-(i Pr) 2 C 6 H 3). 9 During this study, we obtained an unprecedented scandium complex which bears both phosphinidene and methylidene ligands. This scandium methylidene phosphini-dene complex reacts with a variety of unsaturated small molecules, and favoring reaction with the methylidene ligand over the phoshinidene ligand. ■ RESULTS AND DISCUSSION A salt elimination reaction of scandium methyl chloride [LSc(Me)Cl] (L = [MeC(NDIPP)CHC(NDIPP)Me] − , DIPP = 2,6-(i Pr) 2 C 6 H 3) 10 with 1 equiv of K[P(H)DIPP] in toluene at room temperature yielded a scandium methyl phosphide [LSc(Me){P(H)DIPP}] (1) in 85% yield. Complex 1 was

International audience; The (NNNN)-type macrocycle 1,4,7-trimethyl-1,4,7,10-tetraazacyclododecane (Me3TACD, 1,4,7-Me3[12]aneN4) reacted with 1 equiv of ZnEt2 under ethane elimination to give the mononuclear ethyl complex [(Me3TACD)ZnEt] (1). Upon treatment of (Me3TACD)H with 2 equiv of ZnEt2, the dinuclear complex [(Me3TACD)(ZnEt)(ZnEt2)] (2) was formed, which was converted with an additional 1 equiv of (Me3TACD)H to 1. Reaction of 1 with PhSiH3 led to the formation of a tetranuclear ethyl hydrido complex [{(Me3TACD)ZnEt}2(ZnEtH)2] (3). Single-crystal X-ray diffraction study revealed 3 to be a centrosymmetric dimer featuring two [(Me3TACD)ZnEt] units coordinated to a [Zn(μ-H)2Zn] core via amido nitrogen atoms of the Me3TACD ligands. Substitution of the two [(Me3TACD)ZnEt] units in 3 by N-heterocyclic carbene IMes [1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] gave [(IMes)ZnEtH]2 (4b). The mixed alkyl hydrido complexes [(IMes)ZnRH]2 (R = Me, 4a; Et, 4b) were alternatively synthesized in quantitative yield by reacting [(IMes)ZnR2] (R = Me, Et) with [(IMes)ZnH2]2 in 2:1 ratio. Methyl complex 4a reacted with CO2 (p(CO2) = 0.5 bar) under facile insertion of CO2 into Zn–H bonds to give dinuclear formate complex [(IMes)ZnMe(O2CH)]2 (5a). Treatment of 4b with CO2 (p(CO2) = 0.5 bar) afforded a mixture of di- and trinuclear formate complexes [(IMes)ZnEt(O2CH)]2 (5b) and [(IMes)2Zn3Et3(O2CH)3] (6) under elimination of one IMes as CO2 adduct IMes·CO2.

A zwitterionic iridium complex of a phosphine, bearing the carba-closo-dodecaborate anion as a ligand substituent, is reported. When tethered directly to a phosphine ligand, the CB11H11– R group engages in agostic-like bonding, utilizing the B–H bonds adjacent to the carbon atom in the cluster. Evidence for the interactions is observed in solution by variable-temperature NMR and also in the solid state by a single-crystal X-ray diffraction study. The bonding between the cluster and the iridium center has also been analyzed computationally and can be described as a double agostic bonding augmented by an overlap of the skeletal electrons of the cluster with the dz2 orbital of the metal. A significant lengthening of a trans-olefin C–C bond suggests that this ligand substituent has a pronounced trans influence, which is in contrast to the unfunctionalized weakly coordinating HCB11H11– anion.

A DFT study of the ring-opening polymerization of lactide (LA) induced by a dinuclear indium catalyst supported by a chiral diamino phenoxy ligand, [(NNHO)InCl]2(μ-Cl)(μ-OEt) (1), is reported. The nature of the active catalyst, mononuclear vs dinuclear, was investigated and was shown to be dinuclear because of the high energetic cost of its dissociation. The selectivity of the system was investigated for the polymerization of LA with the dinuclear (R,R/R,R)-1 catalyst. In complete agreement with experimental results we observed that (1) selectivity is controlled by the nucleophilic addition of LA to the alcoholate, resulting in the chain-end control of polymerization, (2) a slight kinetic preference for the polymerization of l-LA over d-LA is found that translates to a krel value of ∼14, which is identical with the experimental value, and (3) when rac-LA is used, no clear preference for d- vs l-LA insertion is found, leading to isotactic PLA.

International audience; The synthesis and X-ray crystal structures of Cp*2Yb(3,3′-Me2bipy) and [Cp*2Yb(3,3′-Me2bipy)][Cp*2YbCl1.6I0.4]*CH2Cl2 are described. In both complexes, the NCCN torsion angles are approximately 40°. The temperature-independent value of nf of 0.17 shows that the valence of ytterbium in the neutral adduct is multiconfigurational, in reasonable agreement with a CASSCF calculation that yields a nf value of 0.27; that is, the two configurations in the wave function are f13(π*1)1 and f14(π*1)0 in a ratio of 0.27:0.73, respectively, and the open-shell singlet lies 0.28 eV below the triplet state (nf accounts for f-hole occupancy; that is, nf = 1 when the configuration is f13 and nf = 0 when the configuration is f14). A correlation is outlined between the value of nf and the individual ytterbocene and bipyridine fragments such that, as the reduction potentials of the ytterbocene cation and the free x,x′-R2-bipy ligands approach each other, the value of nf and therefore the f13:f14 ratio reaches a maximum; conversely, the ratio is minimized as the disparity increases.

The ambiphilic species Al(C6H4(o-PPh2))3 (2) was synthesized and fully characterized, notably using X-ray diffraction. Species 2 exhibits pseudo-bipyramidal-trigonal geometry caused by the two Al–P interactions. 2 reacts with CO2 to generate a CO2 adduct commonly observed in the activation of CO2 using frustrated Lewis pairs (FLPs). This ambiphilic species serves as a precatalyst for the reduction of CO2 in the presence of catecholborane (HBcat) to generate CH3OBcat, which can be readily hydrolyzed in methanol. The reaction mixture confirms that, in the presence of HBcat, 2 generates the known CO2 reduction catalyst 1-Bcat-2-PPh2-C6H4 (1) and intractable catecholate aluminum species. It was, however, possible to isolate a single crystal of Al(κ2O,O-(MeO)2Bcat)3 (5) supporting this hypothesis. Also, a borane-protected analogue of 2, Al(C6H4(o-PPh2·BH3))3 (4), does not react with catecholborane, suggesting the influence of the pendant phosphines in the transformation of 2 into 1.

A new boratabenzene-phosphine ligand, di-tert-butylphosphidoboratabenzene, [DTBB]−, has successfully been synthesized by reduction of the corresponding di-tert-butylchlorophosphidoborabenzene compound (2). The species was structurally characterized with both K+ (3) and 18-crown-6·K+ (4) as counterions. Reactions of two equivalents of di-tert-butylphosphidoboratabenzene with NiBr2(PPh3)2, PtCl2, and PtCl2(COD) were undertaken and were successful in yielding three new organometallic boratabenzene species, (μ-κ-η6-C5H5BP(tBu)2)2Ni2 (5), (η3-(C,B,P)-C5H5BP(tBu)2)2Pt (6), and (η3-(C,B,P)-C5H5BP(tBu)2)(κ-C8H12(P(tBu)2BC5H5)Pt (7), respectively. The di-tert-butylphosphidoboratabenzene species displays a remarkable tendency to coordinate to transition metal species in two distinct modes closely associated with other reported boratabenzene and allyl-like interactions. Also of interest is the ability for di-tert-butylphosphidoboratabenzene to be able to coordinate within monomeric as well as dimeric transition meta...

The experimental reaction of [1,2,4-(Me3C)3C5H2]2CeH, Cp′2CeH, and CH3OSO2CH3 begins by α-C–H activation of the SCH3 group, forming Cp′2CeCH2SO2(OCH3), which evolves into Cp′2CeOCH3 with elimination of CH2 (and presumably SO2). Prolonged heating of this mixture (days at 60 °C) forms Cp′2CeOSO2CH3 and CH3OCH3. The metallacycle [1,2,4-(Me3C)3C5H2][1,2-(Me3C)2-4-(Me2CCH2)C5H2]Ce, when presented with the choice of C–H bonds in CH3S and CH3O groups, deprotonates both with comparable rates, ultimately forming Cp′2CeOCH3 and Cp′2CeOSO2CH3 at 20 °C. The experimental studies are illuminated by DFT calculations on the experimental systems, which show that the hydride selects the more acidic CH3S bond, whereas the metallacycle reacts with C–H bonds of both the CH3S and CH3O groups of CH3OSO2CH3. In the metallacycle reaction, the initially formed regioisomers, Cp′2CeCH2SO2(OCH3) and Cp′2CeCH2OSO2CH3, rearrange to the observed products, Cp′2CeOCH3 and Cp′2CeOSO2CH3, respectively. Furthermore, C–H activation at the SCH...

The mechanism of the ring-opening polymerization (ROP) of e-caprolactone by the rare-earth borohydride cations [YMe(BH4)(THF)5]+ has been investigated at the DFT level. The reaction with [YMe(BH4)(...

cited By 42; International audience; The triphosphine-indane TPI ([o-i-Pr2P(C6H 4)]3In) has been prepared and found to react with [Pd(P-t-Bu3)2] and [AuCl(SMe2)]. According to X-ray diffraction analyses and DFT calculations, the ensuing complexes both display original donor-acceptor M→In interactions, although of markedly different nature and magnitude. © 2011 American Chemical Society.

We report theoretical investigations of the reaction of [((MeArO)3mes)U] with CO2 in order to support previously reported experimental data. Experimentally, the reaction in toluene leads to the imm...

Efforts to install the bis(8-quinolyl)methylsilyl (Me-NSiN; 1 = Me-NSiNH) and bis(8-quinolyl)phenylsilyl (Ph-NSiN; 2 = Ph-NSiNH) ligands onto nickel are described. Reaction of 1 with NiCl2(DME) and...

The experimental CO stretching frequencies in the 1:1 adducts between (C5H5-nRn)3U and CO range from 1976 cm-1 in (C5H4SiMe3)3U(CO) to 1900 cm-1 in (C5HMe4)3U(CO). The origin of the large difference between the stretching frequencies in free (2143 cm-1) and coordinated CO and the large effect the substituents on the cyclopentadienyl ligands play in the difference is explored by DFT calculations with a small core effective core potential in which 32 electrons on uranium are explicitly treated. The results of these calculations, along with a NBO analysis, show that a sigma-bond is formed between CO and an empty sigma-orbital on the Cp'3U fragment composed of f sigma and d sigma parentage orbitals. The backbonding interaction, which results in lowering the CO stretching frequency, does not originate from non-bonding metal-based orbitals but from the filled ligand-based orbitals of pi-symmetry that are used for bonding in the Cp'3U fragment. This model, which is different from the backbonding model used in the d-transition metal complexes, rationalizes the large substituent effect in the 5f-metal complexes.

In this paper, a theoretical investigation of bond activations of PhSiH3, catalyzed by Cp2SmH, is proposed by examination of the energy profiles of these reactions. The formation of the minor and major products observed experimentally is rationalized. The experimentally proposed two-step mechanism, starting with a Si−C activation to give Cp2SmPh as an intermediate, is confirmed. The second step involves reaction of this intermediate with the Si−H bond of PhSiH3 to give Ph2SiH2 and regenerate the samarium hydride. The relative free enthalpy barriers of these two steps are in agreement with the lack of observation of any intermediate during the catalytic reaction. In addition to the main experimentally proposed mechanism, a second mechanism that involves two successive Si−H activations is proposed in order to account for the formation of byproducts. Theoretically, these two reactions are demonstrated to occur competitively, which explains the formation of secondary products arising from redistribution and d...

The coordination of a bis(NHC)pyridyl (NHC = N-heterocyclic carbene) ligand to d0 fragments of group 3, lanthanide, and actinide series (M = Sc, Y, La, Sm, Lu, U, and Am) has been theoretically investigated at the DFT level. The influence of the π-donation ability of the co-ligand has been emphasized by comparing the trichloro, trisamido fragments and bare ions. The coordination of the tridentate CNC ligand is dominated by the ligand→metal σ-donations, but unprecedented Nam→Ccarb “back-bonding” was evidenced in the trisamido complexes of La, Sm, and Am. The ability of the bis(NHC)pyridine ligand B for lanthanide/actinide differentiation has been examined, substantiating the critical influence of the electronic properties of the co-ligand and carbene moieties.

The reactions between [1,2,4-(Me3C)3C5H2]2CeH, referred to as Cp′2CeH, and CH3X, where X is Cl, Br, I, OMe, and NMe2, are described. The reactions fall into three distinct classes. Class a, where X = Cl, Br, and I, rapidly form Cp′2CeX and CH4 without formation of identifiable intermediates in the 1H NMR spectra. Class b, where X = OMe, proceeds rapidly to Cp′2Ce(η2-CH2OMe) and H2 and then to Cp′2CeOMe and CH4. The methoxymethyl derivative is sufficiently stable to be isolated and characterized, and it is rapidly converted to Cp′2CeOMe in the presence of BPh3. Class c, where X = NMe2, does not result in formation of Cp′2CeNMe2, but deuterium labeling experiments show that H for D exchange occurs in NMe3. Density functional calculations DFT(B3PW91) on the reaction of (C5H5)2CeH, referred to as Cp2CeH, and CH3X show that the barrier for α-CH activation, resulting in formation of Cp2Ce(η2-CH2X), proceeds with a relatively low activation barrier (ΔG⧧), but the subsequent ejection of CH2 and trapping by H2 has...

The reaction of various actinide and transition metal bisalkyl complexes with pyridine N-oxide has been investigated at the DFT level for M = Zr, Th, and U. Rather than the expected oxygen transfer...

The (FluPPh2NAr) and (IndPPh2NAr) ligands 2a–c and 4a–c (a, Ar = Ph; b, R = DIPP; c, = Mes) were readily prepared by Staudinger reactions between aryl azides and Flu/Ind diphenylphosphines, and the...

The coordination of the four model amino−carbene ligands A−D to SmCl3 has been theoretically investigated. Strong coordination energies were predicted for all carbenes (ΔG(25 °C) < −35 kcal mol-1 for the monoadducts). The nature of the Sm−carbene bonds was studied by molecular orbital and natural bond orbital (NBO) analyses. No evidence for significant carbene-to-Sm π-donation or Cl-to-carbene back-donation was observed. The strong Sm−carbene bonds, culminating in the abnormal NHC species D, can thus be essentially attributed to carbene-to-Sm σ-donation.

A DFT study of the catalytic properties of Cp2ScCH3 and Cp2LuCH3 in the hydromethylation of propene has been performed. The catalytic behavior of Cp2ScCH3 is confirmed, and the formation of secondary products is rationalized. It is shown that Cp2LuCH3 cannot exhibit catalytic behavior and that only stoichiometric conversion of propene to isobutane could be observed. The difference in reactivities between the two metallocenes has been investigated, and an electronic explanation is given based on differences in the coordination of propene. However, the intrinsic reactivities of the two metallocenes is proposed to be driven by both electronic and steric effects.

The fluorenyl-phosphazene ligand 2 has been prepared and coordinated to the RhI(nbd) fragment. X-ray analyses and DFT calculations substantiate the preference of the re-sulting complex 3 for κ2-N,C...

The results of DFT calculations have been used to define the trends in the interactions of H2, N2, C2H4, C2H2, and C2Me2 with the bivalent lanthanide metallocenes Cp2M (Cp = η5-C5H5) and Cp*2M (Cp* = η5-C5Me5), where M = Sm, Eu, Yb. These results, together with those previously published for the bonding of CO to Cp2M (M = Ca, Eu, Yb), suggest that the interaction of these ligands with the lanthanide metallocenes results from a subtle balance between attractive (dipole−dipole or dipole−induced dipole) and repulsive (electron−electron repulsion within the f shell) forces. The balance between the attractive and repulsive forces, and therefore the net bond energy, depends on the f-electron count in these bivalent lanthanide metallocenes. The computational results are compared with experimental observations on paramagnetic Cp*2Eu and diamagnetic ytterbocene, Cp*2Yb.