The first uranyl-methine carbon bond; a complex with out-of-plane uranyl equatorial coordination

Treatment of [UO2Cl2(thf)3] in thf with one equivalent of [Na(CH(Ph2P = NSiMe3)2)] yields an unusual uranyl chloro-bridged dimer containing a uranium(VI)-carbon bond as part of a tridentate bis(iminophosphorano)methanide chelate complex. The methine carbon is displaced significantly from the uranyl equatorial plane.     

The first uranyl complexes with valerate ions

FT–IR spectroscopy and single‐crystal X‐ray structure analysis were used to characterize the discrete neutral compound diaquadioxidobis(n‐valerato‐κ²O,O′)uranium(VI), [UO₂(C₄H₉COO)₂(H₂O)₂], (I), and the ionic compound potassium dioxidotris(n‐valerato‐κ²O,O′)uranium(VI), K[UO₂(C₄H₉COO)₃], (II). The U^VI cation in neutral (I) is at a site of 2/m symmetry. Potassium salt (II) has two U centres and two K⁺ cations residing on twofold axes, while a third independent formula unit is on a general position. The ligands in both compounds were found to suffer severe disorder. The FT–IR spectroscopic results agree with the X‐ray data. The composition and structure of the ionic potassium uranyl valerate are similar to those of previously reported potassium uranyl complexes with acetate, propionate and butyrate ligands. Progressive lengthening of the alkyl groups in these otherwise similar compounds was found to have an impact on their structures, including on the number of independent U and K⁺ sites, on the coordination modes of some of the K⁺ centres and on the minimum distances between U atoms. The evolution of the KUO₆ frameworks in the four homologous compounds is analysed in detail, revealing a new example of three‐dimensional topological isomerism in coordination compounds of U^VI.     

Synthesis and reactions of the first cyclopentadienyl isonitriles

6-Azidofulvenes without a further substituent in the exocyclic position were transformed into new 1-isocyano- and 2-isocyanocyclopenta-1,3-dienes by photolysis in methanol. These novel functionalized cyclopentadienes are useful building blocks, e.g. as dienes in Diels-Alder reactions.     

Isolation of a tetrameric cation-cation complex of pentavalent uranyl

A polymetallic assembly containing mutually coordinated highly reactive UO2+ groups was isolated in the presence of dibenzoylmethanate. NMR studies showed unambiguously the presence of the cation-cation complex in pyridine solution while more polar solvents lead to the disruption of the UO2+/UO2+ interaction and increased stability.     

The first slipped pseudo-quadruple-decker complex of phthalocyanines

The first slipped pseudo-quadruple-decker complex of phthalocyanines was formed unexpectedly upon treatment of the protonated double-decker SmIIIH(Pc)[Pc(alpha-OC4H9)8] with NaOH. The supramolecular structure contains two double-decker units linked by two sodium ions by an extremely rare coordination mode of phthalocyanines in which an aza nitrogen atom and two oxygen atoms from neighboring alkoxy substituents form a tridentate ligand.     

The first phosphite complex of a metalloporphyrin

(Di­phenyl phosphite‐κO)(5,10,15,20‐tetra­phenyl­porphyrinato‐κ⁴N)­manganese(III) hexa­fluoro­antimonate(V), [Mn(C₄₄H₂₈N₄)(C₁₂H₁₁O₃P)](SbF₆), is the first example of a structurally characterized di­aryl or di­alkyl phosphite complex of a metal–porphyrin ion. The axial phosphite ligand binds to the Mn^III ion via the P=O O atom, affording a nominally five‐coordinate complex with an Mn—O distance of 2.120 (4) Å. The mean porphyrin Mn—N distance is 2.000 (4) Å and the Mn^III ion is displaced from the 24‐atom porphyrin mean plane by 0.1548 (13) Å towards the axial O atom. The porphyrin adopts a marked saddle conformation, with a small domed component. The saddle distortion of the porphyrin ligand reflects the tight back‐to‐back dimers formed in the lattice by pairs of neighboring cations. The `non‐covalent' dimers in the lattice exhibit an unusual (weak) η²‐type coordination of a pyrrole C=C bond from a neighboring mol­ecule, with Mn^III⃛C distances of 3.697 (5) and 3.537 (5) Å.     

Synthesis of the first metallacarborane triple-decker complexes with a central cyclopentadienyl ligand

The previously unknown metallacarboranes (η-C₅R₅)Ru(η-9-Me₂S-7,8-C₂B₉H₁₀) (R=H or Me) and (η-C₅H₅)Ni(η-9-Me₂S-7,8-C₂B₉H₁₀) were prepared and used in the synthesis of the first metallacarborane triple-decker complexes with a central cyclopentadienyl ligand, viz., [(η-C₅R₅)Ru(μ-η:η-C₅Me₅)Ru(η-9-Me₂S-7,8-C₂B₉H₁₀)]PF₆ (R=H or Me), [(η-9-Me₂S-7,8-C₂B₉H₁₀)Ni(μ-η:η-C₅H₅)Ni(η-9-Me₂S-7,8-C₂B₉H₁₀)]PF₆, and [(η-C₅H₅)Ni(μ-η:η-C₅H₅)Ni(η-9-Me₂S-7,8-C₂B₉H₁₀)]BF₄. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1368–1373, July, 1999.     

The first heteronuclear liquid crystal metal complex

Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2462–2463, October, 1990.     

Triphenyl phosphine complex of cyclopentadienyl(manganese dicarbonyl triphenyl phosphine) gold

Conclusions The triphenyl phosphine complex of cyclopentadienyl (manganese dicarbonyl triphenyl phosphine) gold was obtained.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2641–2642, November, 1973.     

On the nature of the first excited states of the uranyl ion

Results of calculations on the uranylion using the LCAO MO Hartree—Fock—Slater method including relativistic effects are reported. The highest occupied molecular orbital is calculated to be σ_u, consisting predominantly of U 5f character. The σ_u orbital is the HOMO partly because of “pushing-from-below” by the U 6p orbital, but also as a result of the change in potential of the U 5f electrons with the uranium core elections brought about by relativistic contraction of the core electrons. This effect also determines the character of the first virtual levels (δ_u and Φ_u, respectively) in equatorial ligand fields.     

Polytypism and oxo-tungstate polyhedra polymerization in novel complex uranyl tungstates

Three new uranyl tungstates, α-, β-Cs(2)[(UO(2))(2)(W(2)O(9))], and Rb(6)[(UO(2))(7)(WO(5))(2)(W(3)O(13))O(2)], have been obtained by high temperature solid state reactions. All three compounds display novel structure topologies: α- and β-Cs(2)[(UO(2))(2)(W(2)O(9))] are based upon layers with a new topology that can be related to the uranophane topology; Rb(6)[(UO(2))(7)(WO(5))(2)(W(3)O(13))O(2)] is a rare example of a non-molecular inorganic phase with layers containing oxo-tungstate trimers. The structural relationship between α- and β-Cs(2)[(UO(2))(2)(W(2)O(9))] can be assigned to polytypism.     

Synthesis of a uranyl persulfide complex and quantum chemical studies of formation and topologies of hypothetical uranyl persulfide cage clusters

The compound Na(4)[(UO(2))(S(2))(3)](CH(3)OH)(8) was synthesized at room temperature in an oxygen-free environment. It contains a rare example of the [(UO(2))(S(2))(3)](4-) complex in which a uranyl ion is coordinated by three bidentate persulfide groups. We examined the possible linkage of these units to form nanoscale cage clusters analogous to those formed from uranyl peroxide polyhedra. Quantum chemical calculations at the density functional and multiconfigurational wave function levels show that the uranyl-persulfide-uranyl, U-(S(2))-U, dihedral angles of model clusters are bent due to partial covalent interactions. We propose that this bent interaction will favor assembly of uranyl ions through persulfide bridges into curved structures, potentially similar to the family of nanoscale cage clusters built from uranyl peroxide polyhedra. However, the U-(S(2))-U dihedral angles predicted for several model structures may be too tight for them to self-assemble into cage clusters with fullerene topologies in the absence of other uranyl-ion bridges that adopt a flatter configuration. Assembly of species such as [(UO(2))(S(2))(SH)(4)](4-) or [(UO(2))(S(2))(C(2)O(4))(4)](4-) into fullerene topologies with ~60 vertices may be favored by use of large counterions.     

Synthesis, characterization, and reactivity of a uranyl beta-diketiminate complex

Addition of 1 equiv of Li(Ar2nacnac) (Ar2nacnac = (2,6-(i)Pr2C6H3)NC(Me)CHC(Me)N(2,6-(i)Pr2C6H3)) to an Et2O suspension of UO2Cl2(THF)3 generates the uranyl dimer [UO2(Ar2nacnac)Cl]2 (1) in good yield. A second species can be isolated in low yield from the reaction mixtures of 1, namely [Li(OEt2)2][UO2(Ar2nacnac)Cl2] (2). The structures of both 1 and 2 have been confirmed by X-ray crystallography. Complex 1 reacts with Ph3PO to generate UO2(Ar2nacnac)Cl(Ph3PO) (3). In addition, 1 reacts with AgOTf and either 1 equiv of DPPMO2 or 2 equiv of Ph2MePO to provide [UO2(Ar2nacnac)(DPPMO2)][OTf] (4) and [UO2(Ar2nacnac)(Ph2MePO)2][OTf] (5), respectively. Both 4 and 5 have been fully characterized, including analysis by X-ray crystallography and cyclic voltammetry. Reduction of 4 with Cp2Co provides UO2(Ar2nacnac)(CH{Ph2PO}2) (6), a uranyl(VI) complex that is generated by the formal loss of H* from the DPPMO2 ligand. Labeling studies have been performed in an attempt to elucidate the mechanism of hydrogen loss. In contrast, reduction of 5 with Cp2Co provides UO2(Ar2nacnac)(Ph2MePO)2 (7), a rare example of a uranyl(V) complex. As expected, the solid-state molecular structure of 7 reveals slightly longer U-O(oxo) bond lengths relative to 5. Furthermore, complex 7 can be converted back into 5 by oxidation with AgOTf in toluene.     

The first synthesised examples of di-siloxy-substituted cyclopentadienyl zirconocenes,their synthesis,structure and activity in ethylene polymerisation

Bis-(1,2-(RMe₂SiO)₂)ZrCl₂ complexes with R = Me-(5a), iPr-(5b) and tBu-(5c) have been synthesised in good yields and characterised. Compounds 5a–c are the first synthesised examples of multi-siloxy-substituted cyclopentadienyl metallocenes. The siloxy-substituents have a for siloxy substituted metallocenes unique steric arrangement, with one almost in the same plane, and the other nearly perpendicular to the plane of the cyclopentadienyl ligand of the zirconocene. The ethylene/1-hexene co-polymerisation activity using methylalumoxane as co-activator gives low activities, with compound 5c (262.92 kg(PE)/g(Zr)/h) being the most active.     

The first thermally stable half-sandwich titanium zwitterionic complex

Thermally stable zwitterionic complex [(η⁵-C₅Me₅)Ti(Ot-Bu)₂]^(δ+)[(μ-Me)B(C₆F₅)₃]^(δ−) (5) was formed by mixing equimolar quantities of [(η⁵-C₅Me₅)TiMe(Ot-Bu)₂] and [B(C₆F₅)₃]. The compound was recrystallized from hot toluene and has been stable so far for 1 year at ambient temperature in the solid state and in toluene solution. The ¹H, ¹⁹F and 1D NOESY NMR spectra in C₆D₆ solution proved the inner sphere ion pair structure of 5. The X-ray crystal structure of 5 revealed that the bridging methyl group is σ-bonded to boron, and all its C-H bonds fulfil criteria for agostic bonding interaction with the titanium atom. In contrast to the stable solution in C₆D₆ compound 5 decomposed in CD₂Cl₂ solvent within hours at room temperature.     

Determination of the stability constants of uranyl complex with 8-hydroxyquinolinium sulfate

8-Hydroxyquinoline (8-HOQ) is known as an important chelating agent for several metal ions. This compound is practically insoluble in water. For this reason, in this study its water soluble sulfate salt has been used for complexing uranyl ions and the stability constants of the complex have been determined. The Irving-Rosotti method computing the Calvin-Bjerrum pH-titration data, was applied. Finally, the stability constants of the complex formed between (8-HOQN-H)₂SO₄ and uranyl ions were found to be lgK₁=8.25 and lgK₂=4.15, the overall stability constant being {ie55-1}.     

The quadrupole moment of substituted cyclopentadienyl anions

Previous work in our group on the cation binding of substituted cyclopentadienyl anions (Cp) showed the curious result that Cp traceless electric quadrupole moments (Θ(zz)) are almost all positive. Probing this issue further here we show that substituted Cp Θ(zz) values are always significantly more positive than the analogous substituted benzenes. Given the nature of aromatic Θ(zz) values, this is the opposite of what would be predicted. Furthermore, we show that the quadrupole moments of Cp anions do not behave as one would expect based on Cp substitutions. Unlike the quadrupole moments of substituted benzenes, which generally become more negative with the addition of electron-donating groups and more positive with the addition of electron-withdrawing groups, Cp quadrupole moments become more positive when any substituent is added, regardless of the electron-donating/withdrawing nature of the substituent. To explain these results we propose a model where the anionic Cp π-electron density repels the substituent electron density toward the molecular periphery and AIM calculations support this view.