Does Gd@C82 have an anomalous endohedral structure? Synthesis and single crystal X-ray structure of the carbene adduct

We report here the results on single crystal X-ray crystallographic analysis of the Gd@C82 carbene adduct (Gd@C82(Ad), Ad = adamantylidene). The Gd atom in Gd@C82(Ad) is located at an off-centered position near a hexagonal ring in the C2v-C82 cage, as found for M@C82 (M = Sc and La) and La@C82(Ad). Theoretical calculation also confirms the position of the Gd atom in the X-ray crystal structure.     

The shape of the Sc2(μ2-S) unit trapped in C82: crystallographic, computational, and electrochemical studies of the isomers, Sc2(μ2-S)@C(s)(6)-C82 and Sc2(μ2-S)@C(3v)(8)-C82

Single-crystal X-ray diffraction studies of Sc(2)(μ(2)-S)@C(s)(6)-C(82)·Ni(II)(OEP)·2C(6)H(6) and Sc(2)(μ(2)-S)@C(3v)(8)-C(82)·Ni(II)(OEP)·2C(6)H(6) reveal that both contain fully ordered fullerene cages. The crystallographic data for Sc(2)(μ(2)-S)@C(s)(6)-C(82)·Ni(II)(OEP)·2C(6)H(6) show two remarkable features: the presence of two slightly different cage sites and a fully ordered molecule Sc(2)(μ(2)-S)@C(s)(6)-C(82) in one of these sites. The Sc-S-Sc angles in Sc(2)(μ(2)-S)@C(s)(6)-C(82) (113.84(3)°) and Sc(2)(μ(2)-S)@C(3v)(8)-C(82) differ (97.34(13)°). This is the first case where the nature and structure of the fullerene cage isomer exerts a demonstrable effect on the geometry of the cluster contained within. Computational studies have shown that, among the nine isomers that follow the isolated pentagon rule for C(82), the cage stability changes markedly between 0 and 250 K, but the C(s)(6)-C(82) cage is preferred at temperatures ≥250 °C when using the energies obtained with the free encapsulated model (FEM). However, the C(3v)(8)-C(82) cage is preferred at temperatures ≥250 °C using the energies obtained by rigid rotor-harmonic oscillator (RRHO) approximation. These results corroborate the fact that both cages are observed and likely to trap the Sc(2)(μ(2)-S) cluster, whereas earlier FEM and RRHO calculations predicted only the C(s)(6)-C(82) cage is likely to trap the Sc(2)(μ(2)-O) cluster. We also compare the recently published electrochemistry of the sulfide-containing Sc(2)(μ(2)-S)@C(s)(6)-C(82) to that of corresponding oxide-containing Sc(2)(μ(2)-O)@C(s)(6)-C(82).     

Is there a general rule for the gauche effect in the conformational isomerism of 1,2-disubstituted ethanes?

The stabilities of the gauche and anti conformations of butane, 1,2-dicyanoethane (DCE), and 1,2-dinitroethane (DNE) have been investigated through theoretical calculations. The gauche effect-the tendency of keeping close vicinal electronegative substituents (thetaX-C-C-X approximately 60 degrees ) in an ethane fragment-is expected to drive the conformational equilibrium of DCE and DNE toward the gauche conformation. It was found that, for butane, where the gauche effect is supposed to be poor/null, the hyperconjugation effect contributes mostly to the anti stabilization in opposition to the traditional sense that the methyl groups repel each other, and this should govern its conformational equilibrium. For DCE the equilibrium was shifted to the anti conformer, essentially due to a gauche repulsion, while for DNE, despite the higher electronic delocalization energies, a predominance of the gauche conformer was obtained, and this was attributed mainly to the attractive dipolar interaction between the two nitro groups. A full orbital energy analysis was performed using the natural bond orbital approach, which showed that bond bending and anti-C-H/C-X* hyperconjugation models, usually applied to explain the origin of the gauche effect in fluorinated derivatives, are not adequate to completely explain the conformational behavior of the titled compounds.     

Molecular structure and fluxional behaviour of the iron-rhodium methoxymethylidyne cluster complex Fe2 Rh(μ-H)(μ3-COCH3)(CO)7(η-C5H5)

The complex Fe₂Rh(μ-H)(μ₃-COCH₃)(CO)₇(η-C₅H₅) prepared by treatment of Fe₃(μ-H)(μ-COCH₃)(CO)₁₀ with Rh(CO)₂ (η-C₅H₅), has been examined by single crystal X-ray diffraction. The compound crystallises in the monoclinic space group C2/c (No. 15) with a 25.409(2), b 8.129(1), c 17.044(1) Å, β 103.744(6)°, V 3419.6(6) ų and D_c 2.02 g cm⁻³ for Z = 8 and M = 519.8. Data were collected for 2° ⩽ θ ⩽ 30° with graphite monochromated X-radiation (Mo-K_α) using an Enraf-Nonius CAD4-F diffractometer. The structure was refined to R = 0.025 (R_itw = 0.037) for 3557 observed [I ⩾ 3(σI)], absorption corrected data. The complex contains an asymmetrically bonded methoxymethylidyne ligand capping an Fe₂Rh triangular face (Fe(1)-C(8) 1.863(3), Fe(2)-C(8) 1.881(3), Rh-C(8), 2.211(3) Å). The terminal carbonyl ligand on the rhodium atom shows slight semi-bridging interactions with the two iron atoms (Fe(1) … C(7) 2.888(4), Fe(2) … C(7), 2.769(4) Å, Rh-C(7)-O(7) 169.1(4)°. The iron—iron vector is spanned by a (directly located) μ-hydride ligand. Variable temperature ¹³C NMR studies reveal fluxional behaviour, including a temperature dependence both of the alkylidyne carbon chemical shift (δ 323.5 at +80°C, δ 319.2 at −90°C) and its ¹⁰³Rh coupling constant (¹J(Rh-C) 23 Hz at −90°C, 26 Hz at +80°C). These data suggest an increased interaction of the ‘semi-μ₃’ alkylidyne ligand with the rhodium centre at higher temperatures, primarily associated with the highest energy fluxional process. Extended Hückel MO calculations on this complex allow a rationalisation of the ‘semi-μ₃’ nature of the COCH₃ group.     

Cluster chemistry. 85. Addition of a gold acetylide to an Ru5 cluster. X-ray structure of AuRu5(μ5-C2PPh2)(μ-C2Ph)(μ-PPh2)(CO)13(PPh3)

The reaction between Ru₅(₅-C₂PPh₂)(-PPh₂)(CO)₁₃ and Au(C₂Ph)(PPh₃) afforded AuRu₅(₅-C₂PPh₂)(-C₂Ph)(-PPh₂)(CO)₁₃ (PPh₃), in which the Ru₅ cluster has a scorpion geometry; the Au(PPh₃) group bridges one of the Ru-Ru bonds of the Ru₃ triangle, while the C₂Ph group bridges one of the tail Ru-Ru vectors.For Part 84, see Ref. 1.     

The critical re-evaluation of the aromatic/antiaromatic nature of Ti3(CO)3: a missed opportunity?

The nature of bonding and aromaticity of Ti(3)(CO)(3), a mill-shaped metal-carbonyl complex, is studied carefully. A unique bonding mechanism between metal and carbonyl groups is found in this species. Ti(3)(CO)(3) is an example of a metal-carbonyl complex with prominent metal to carbonyl donation. Moreover, it is proven that not only is Ti(3)(CO)(3) not an antiaromatic complex but also it is the first synthesized example of d-block, σ+π aromatic species. A quick survey among the first row of transition metals in the periodic table shows that other local minima with similar structures and aromaticity are present and Ti(3)(CO)(3) is the first synthesized species of an unknown family.     

Synthesis and crystal structure of [(η3-C3H5)(CO)2Mo(μ-S2CPCy3)-Mo(η3-CH2CMeCH2)(CO)2]

A novel dimolybdenum complex [(³-C₃H₅)(CO)₂Mo(-S₂CPCy₃)Mo(³-CH₂CMeCH₂)(CO)₂], obtained by reacting the [(CO)₂(³-C₃H₅)Mo(-S₂CPCy₃)Mo(CO)₃]^– anion with an excess of ClCH₂CMe=CH₂, has been characterized by i.r., ³¹P{¹H}, ¹H- and ¹³C-n.m.r. spectroscopy and by elemental analysis. The crystal structure of the complex, determined by X-ray diffraction, shows a definite preference for the central carbon of the S₂CPCy₃ bridge to bind to the Mo(2) atom coordinated by ³-2-methylallyl, rather than the Mo(1) atom attached to unsubstituted ³-allyl ligand.     

The oxidative addition of SnCl4 to [W(CO)4(NCMe)(PPh3)]. The X-ray crystal structure of [WH(CO)3(NCMe)(PPh3)2][SnCl5·MeOH]

The oxidative addition reaction of SnCl₄ with [W(CO)₄(NCMe)(PPh₃)] in acetonitrile gives a mixture of seven-coordinate tungsten(II) compounds: [WCl(SnCl₃)(CO)₃(NCMe)(PPh₃)] (1), [WCl₂(CO)₃(NCMe)(PPh₃)] (2), [WCl(SnCl₃)(CO)₂(NCMe)₂(PPh₃)] (3), and [WCl₂(CO)₂(NCMe)₂(PPh₃)] (4) identified by IR and NMR (¹H, ¹³C{¹H}, and ³¹P{¹H}) studies. Treatment of [W(CO)₄(NCMe)(PPh₃)] with 1 equiv. of SnCl₄ in CH₂Cl₂ solution besides compounds 1 and 2 also gives ionic species such as [HPPh₃]⁺ and [SnCl₆]²⁻ and cationic tungsten(II) complexes. The crystal structure of one of these, [WH(CO)₃(NCMe)(PPh₃)₂][SnCl₅·MeOH] (5), has been established by single-crystal X-ray diffraction. The IR, ¹H, ¹³C{¹H} and ³¹P{¹H} spectra of 5 are also described and can be correlated with the crystallographically observed geometry. A notable feature of 5 is the presence of an agostic interaction of the hydride ligand with one of the carbonyl ligands.     

ESR study of reactivity of the complex (η2-C60)Os(CO)(PPh3)2(CNBut) toward free radicals

Addition of the ^·P(O)(OPrⁱ)₂, Me^·, Et^·, ^·Bu^t, and Cl₃C^· radicals to the (ν²-C₆₀)Os(CO)-(PPh₃)₂(CNBu^t) complex (1) was studied by ESR spectroscopy. The spectral parameters of the spin-adducts of these radicals with complex 1 were determined. The predominant direction of the attack by the ^·P(O)(OPrⁱ)₂, ^·Bu^t, and Cl₃C^· radicals are the cis-1 and cis-2 bonds of the fullerene molecule. The stability of the spin-adducts depends substantially on the nature of the added radical. The addition rate constants of the ^·P(O)(OPrⁱ)₂, ^·But, and Cl₃C^· radicals to complex 1 and the dimerization rate constants for these spin-adducts were determined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 301–307, February, 2008.     

The synthesis and crystal structure of novel Mo-Sn tetranuclear cubane-like cluster [Mo3(SnBr3)(μ3-O)(μ3-S)3(dtp)3(py)3]·(CH2Cl2)

The synthesis and crystal structure of the first example for hybrid Sn-Mo tetranuclear cubane-like cluster compound containing S/O mixed triple capping atom [Mo₃(SnBr₃)(μ ₃-O)(μ ₃-S)₃(dtp)₃(py)₃]·(CH₂Cl₂) (A) (dtp=S₂P(OC₂H₅)₂) are reported. The compound is prepared by the reaction of [Mo₃(μ ₃-O)(μ-S)₃(dtp)₄·(H₂O)] with SnBr ₃ ^? . The molecular structure of the cluster can be described as a [Mo₃OS₃] core with the SnBr ₃ ^? fragment linked to {Mo₃} triangle by three (μ ₃-S). Three Mo-Mo bond lengths are 2.616(2), 2.620(2), 2.628(2) Å, respectively, and the molecule has approximately C_3v symmetry. There is no bonding between Sn and Mo atoms, however, the addition of SnBr ₃ ^? may cause electron transfer from Sn²⁺ to [Mo₃OS₃] core to result in the shortening of Mo-Mo bond distances. The compound crystallizes in the monoclinic space group P2₁/n with refined lattice parameters ofa=13.012(4),b=22.877(6),c=18.585(6) Å,β=96.34(3)°,V=5498(3)ų, andZ=4. Full matrix refinement converged with final agreement factor ofR=0.054,R _w=0.064.     

The mechanism of fluxionality of (1,2,7-η3-2-Me-benzyl)(η5-C5H5)Mo(CO)2

It is shown that (1,2,7-η³-2-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits in solution as one isomer which is fluxional, probably via (7-η¹-2-Me-benzyl)((η⁵-C₅H₅)Mo(CO)₂, with ΔG^≠₃₇₀ = 23.6 ± 1.0 kcal mol⁻¹. In contrast, (1,2,7-η³-3-Me-benzyl)(η⁵-C₅H₅)Mo(CO)₂ exits as two isomers at −20°C, which undergo interconversion at room temperature with ΔG^≠ 15.7 kcal mol⁻¹. This dynamic process is an allyl rotation. It is probable that there is also a low energy [1,5]-sigmatropic shift.     

The asymmetric sythesis of (-)-actinonin using the iron chiral auxiliary [(η5-C5H5)Fe(CO)(PPh3)]

The asymmetric synthesis of the α-pentyl succinate fragment of (-)-Actinonin is achieved using the chiral iron acetyl S-(+)-[(η⁵-C₅H₅)Fe(CO)(PPh₃)COCH₃] and subsequently converted to (-)-Actinonin in an overall yield of 41%.     

Triple C-H Bond Activation of a Nickel-Bound Methyl Group: Synthesis and X-Ray Structure of a Carbide Cluster (NiCp)(6)(μ(6)-C)

A new hexanuclear cyclopentadienylnickel carbide cluster (NiCp)(6)(μ(6)-C) (1) was obtained through the thermolysis of the alkene complex [NiCp(CH(3))(η(2)-CH(2)═CHC(4)H(9))] (4). The X-ray molecular structure of 1 (monoclinic; P2(1)/c; Ni-C(carbide) = 1.767(4)-2.109(4) ?) reveals a highly deformed octahedral arrangement of nickel atoms with two octahedron edges opened (Ni-Ni bonding distances = 2.410(1)-2.623(1) ?, Ni···Ni nonbonding distances = 3.107(2) and 3.108(2) ?). Cluster 1 is the first example of a homoleptic, cyclopentadienylnickel carbide cluster. Moreover, (13)C-labeling studies proved that the carbido ligand in cluster 1 originated from the Ni-bound methyl group. This transformation requires a triple C-H bond activation in the methyl group, which has not been observed so far for late transition metal compounds.     

Can the bis(diboranyl) structure of B(4)H(10) be observed? The story continues

Pathways for the conversion of the unknown bis(diboranyl) isomer of tetraborane(10) (B(4)H(10)) to the known arachno isomer have been determined for the first time with the use of an electron correlation ab initio quantum chemical method and without the use of constraints in determination of the transition structures. Two isomers of tetraborane(10), one new, with a pentacoordinated boron atom have been found on the theoretical potential energy surface. Several other pathways for molecular rearrangement of tetraborane(10) have also been characterized. The theoretical method was MP2 theory with the 6-31G(d,p) basis set. The most likely pathway for the conversion of the bis(diboranyl) isomer of tetraborane(10) to the arachno isomer is a concerted pathway with two pentacoordinated intermediates. The highest energy transition state for this pathway lies 27.7 kcal/mol above the bis(diboranyl) isomer. At the same level of the theory, the bis(diboranyl) isomer lies 9.2 kcal/mol above the known arachno isomer. The two isomers with a pentacoordinated boron atom lie 12.5 and 13.1 kcal/mol above the arachno isomer.     

Further studies of the reactions of PtRu5(μ6-C)(CO)16 with alkynes: The preparation and structural characterizations of PtRu5(CO)13(μ-EtC2Et)(μ3-EtC2Et)(μ5-C) and Pt2Ru6(CO)17(μ-η5-Et4C5)(μ3-EtC2Et) (μ6-C)

The reaction of PtRu₅(CO)₁₆(μ₆-C),1 with 3-hexyne in the presence of UV irradiation produced two new electron-rich platinum-ruthenium cluster complexes PtRu₅(CO)₁₃(μ-EtC₂Et)(μ₃-EtC₂Et)(μ₅-C),2 (20% yield) and Pt₂Ru₆(CO)₁₇(μ-η⁵-Et₄C₅)(μ₃-EtC₂Et) (μ₆-C),3 (7% yield). Both compounds were characterized by single-crystal X-ray diffraction analyses. Compound2 contains of a platinum capped square pyramidal cluster of five ruthenium atoms with the carbido ligand located in the center of the square pyramid. A EtC₂Et ligand bridges one of the PtRu₂ triangles and the Ru-Pt bond between the apical ruthenium atom and the platinum cap. The structure of compound3 consists of an octahedral PtRu₅ cluster with an interstitial carbido ligand and a platinum atom capping one of the PtRu₂ triangles. There is an additional Ru(CO)₂ group extending from the platinum atom in the PtRu₅ cluster that contains a metallated tetraethylcyclopentadienyl ligand that bridges to the platinum capping group. There is also a EtC₂Et ligand bridging one of the PtRu₂ triangular faces to the capping platinum atom. Compounds2 and3 both contain two valence electrons more than the number predicted by conventional electron counting theories, and both also possess unusually long metal-metal bonds that may be related to these anomalous electron configurations. Crystal data for2, space group Pna2₁,a=19.951(3) Å,b=9.905(2) Å,c=17.180(2) Å,Z=2, 1844 reflections,R=0.036; for3, space group Pna2₁,α=13.339(1) Å,b=14.671(2) Å,c=11.748(2) Å, α=100.18(1)°, β=95.79(1)°, γ=83.671(9)°,Z=2, 3127 reflections,R=0.026.     

Crystal structure and fluorescence spectrum of the complex [Eu(Ⅲ)(TTA)_3(phen)]

The title complex Eu(Ⅲ)(TTA)3(phen) (where TTA= thenoyltrifluoroacetone monoanion; phen = 1,10-phenanthroline) has been synthesized in mixed solvents of acetone and ethanol (1:1 volume ratio) and its crystal structure has been determined by X-ray diffraction. The complex crystals are triclinic, space group P1(#2) with cell dimensions of a = 1.3241 (2) nm, 6 = 1.5278(4) nm, c = 0.9755(3) nm, α = 92.49 (2)°, β=102.57(2)°, γ = 91.62(2)°, V=1.9268(8) nm3, Z = 2, μ(Mo Kα) = 18.77 cm-1, Dx = 1.720 g/cm3. The coordination geometry of Eu atom is a distorted square antiprism, and the encapsulated structure that can meet the structural requirement of the typical europium luminescent sensor. The fluorescence spectrum suggests that the complex is a strong photoluminescent material.     

Is the Trigonal Prismatic Distortion the Answer for the Geometry of InIII four Members Dithiochelate Compounds? The Crystal and Molecular Structure of In(S2AsR2)3 (R = Me,Ph)

The distortion from the octahedral geometry is discussed for Indium(III) 1,1‐dithio complexes (dithiophosph(in)ates, dithiocarbamates, dithioarsinates) and isostructural chromium(III) compounds in relation with the bite of the ligands, the S…S repulsion within the four members rings and S…S interligand distances. The crystal and molecular structures of In(S₂AsR₂)₃ (R = Me, Ph) have been determined by single crystal X‐ray diffraction. The dithioarsinate ligands are basically monomeric and isobidentate, with average values for arsenic‐sulphur bond distances of 2.135 Å for dimethyl and 2.137 Å for diphenyl complex. The average In–S distances are identical (2.634 Å) in both cases.     

The formation and molecular structure of (η5-C5H5)3Sm · OC4H8

Reaction of 1/2 mole ratio of (η⁵-C₅H₅)SmCl₂ ·3THF and NaCCCH₂OCH₂CHCH₂ in THF solution resulted in the formation of (η⁵-C₅H₅)Sm·OC₄H₈; the complex crystallizes in monoclinic space group P2₁/n with unit cell constants a = 8.254(5), b = 24.63(1), c = 8.339(3) Å, β = 101.33(5)° and D_c = 1.67 g/cm³ for Z = 4. Refinement has led to a final R value of 0.041 based on 2106 independent observed reflections. The THF molecule is coordinated to the samarium atom at a SmO distance of 2.522(6) Å. The SmC(cyclopentadienyl) bond lengths range from 2.70(1) to 2.80(1) Å and average 2.742(1) Å. A comparison of some significant structural parameters along the isostructural series (η⁵-C₅H₅)₃Ln·THF (LnLa, Pr, Nd, Gd, Dy, Lu and Sm) with the ionic radii of Ln³⁺ was made.