Lanthanide Analogues Research Articles

Infra-red and Raman spectroscopic study of tetra-substituted bis(phthalocyaninato) rare earth complexes peripherally substituted with tert-butyl derivatives

The infra-red spectroscopic data for a series of 13 homoleptic substituted bis(phthalocyaninato) rare earth complexes with tervalent rare earths M III(TBPc) 2 [M = Y, Pr, …, Lu except La, Ce and Pm; TBPc = dianion of 3(4),12(13),21(22),30(31)-tetra( tert-butyl)-phthalocyanine] have been collected with resolution of 2 cm −1. Raman spectroscopic properties in the range of 500–1800 cm −1 for these double-deckers M III(TBPc) 2 have been collected using laser excitation sources emitting at 632.8 nm. Both the IR and Raman spectra for M III(TBPc) 2 are more complicated than those of homoleptic bis(phthalocyaninato) rare earth analogues due to the decreased molecular symmetry of these double-decker compounds. For this series, the IR typical marker band of (TBPc) − appears as an intense absorption at 1314–1319 cm −1, attributed to the pyrrole stretching. Under excitation at 632.8 nm that is in close resonance with the main Q absorption band of phthalocyanine ligand, typical Raman marker band of the monoanion radical (TBPc) − was observed at 1515–1530 cm −1 resulting from aza C N stretching. Both techniques reveal that the frequencies of pyrrole stretching, isoindole breathing and aza stretchings depend on the rare earth ionic size, shifting to higher energy along with the lanthanide contraction due to the increased ring–ring interaction across the series.

Vibrational spectroscopy of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes: Part 14. The infrared and Raman characteristics of phthalocyanine in “pinwheel-like” homoleptic bis[1,8,15,22-tetrakis(3-pentyloxy)phthalocyaninato] rare earth(III) double-decker complexes

The infrared (IR) spectroscopic data and Raman spectroscopic properties for a series of 13 “pinwheel-like” homoleptic bis(phthalocyaninato) rare earth complexes M[Pc(α-OC 5H 11) 4] 2 [M = Y and Pr–Lu except Pm; H 2Pc(α-OC 5H 11) 4 = 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine] have been collected and comparatively studied. Both the IR and Raman spectra for M[Pc(α-OC 5H 11) 4] 2 are more complicated than those of homoleptic bis(phthalocyaninato) rare earth analogues, namely M(Pc) 2 and M[Pc(OC 8H 17) 8] 2, but resemble (for IR) or are a bit more complicated (for Raman) than those of heteroleptic counterparts M(Pc)[Pc(α-OC 5H 11) 4], revealing the decreased molecular symmetry of these double-decker compounds, namely S 8. Except for the obvious splitting of the isoindole breathing band at 1110–1123 cm −1, the IR spectra of M[Pc(α-OC 5H 11) 4] 2 are quite similar to those of corresponding M(Pc)[Pc(α-OC 5H 11) 4] and therefore are similarly assigned. With laser excitation at 633 nm, Raman bands derived from isoindole ring and aza stretchings in the range of 1300–1600 cm −1 are selectively intensified. The IR spectra reveal that the frequencies of pyrrole stretching and pyrrole stretching coupled with the symmetrical C H bending of –CH 3 groups are sensitive to the rare earth ionic size, while the Raman technique shows that the bands due to the isoindole stretchings and the coupled pyrrole and aza stretchings are similarly affected. Nevertheless, the phthalocyanine monoanion radical Pc′ − IR marker band of bis(phthalocyaninato) complexes involving the same rare earth ion is found to shift to lower energy in the order M(Pc) 2 > M(Pc)[Pc(α-OC 5H 11) 4] > M[Pc(α-OC 5H 11) 4] 2, revealing the weakened π–π interaction between the two phthalocyanine rings in the same order.

Influence of Steric and Electronic Properties of the Defect Site, Lanthanide Ionic Radii, and Solution Conditions on the Composition of Lanthanide(III) α1-P2W17O6110- Polyoxometalates

This study identifies the principles that govern the formation and stability of Ln complexes of the (alpha(1)-P(2)W(17)O(61))(10-) isomer. The conditional stability constants for the stepwise formation equilibria, K(1cond) and K(2cond), determined by (31)P NMR spectroscopy, show that the high log K(1cond)/log K(2cond) ratio predicts the stabilization of the 1:1 Ln/ (alpha(1)-P(2)W(17)O(61))(10-) species. The value of log K(1cond) increases as the Ln series is traversed, consistent with the high charge/size requirement of the basic alpha(1) defect site. The conditional stability constants, K(2), are very low and are highly dependent on the countercations in the buffer. The source of the instability is understood from the crystal structures of the early-mid lanthanide analogues, where the close contact of the (alpha(1)-P(2)W(17)O(61))(10-) units result in severe steric encumbrance. The electronic properties of the alpha(1) defect along with the lanthanide ionic radii and countercation composition are important parameters that need to be considered for a rational synthesis of lanthanide polyoxometalates.

Infrared spectra of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes: Part 12. The infrared characteristics of phthalocyanine in heteroleptic bis(phthalocyaninato) rare earth complexes

The infra-red (IR) spectroscopic data for a series of 13 heteroleptic bis(phthalocyaninato) rare earth complexes M(Pc)[Pc(OC 8H 17) 8] [M = Y, Pr, …, Lu except Pm; H 2Pc = phthalocyanine; H 2Pc(OC 8H 17) 8 = 2,3,9,10,16,17,24,25-octakis(octyloxy)phthalocyanine] have been collected with resolution of 2 cm −1. The IR spectra for M(Pc)[Pc(OC 8H 17) 8] are more complicated than those of homoleptic bis(phthalocyaninato) rare earth counterparts M(Pc) 2 and M[Pc(OC 8H 17) 8] 2 due to the decreased molecular symmetry of these double-decker compounds, C 4v. For this series of heteroleptic bis(phthalocyaninato) rare earth compounds, the Pc − marker band at 1315–1322 cm −1, attributed to the pyrrole stretching, is found to be dependent on the central rare earth size, shifting slightly to the higher energy along with the decrease of rare earth radius. The coupling of isoindole deformation and aza stretching at 1057–1063 cm −1 and the coupling of pyrrole and aza stretching at 1497–1504 cm −1 are also metal-sensitive. The frequency of the vibration at 880–884 cm −1 is also dependent on the rare earth ionic size. The assignments of the vibration bands for these compounds have been made by comparison with the IR spectra of unsubstituted and in particular the 2,3,9,10,16,17,23,24-octakis(octyloxy)-substituted bis(phthalocyaninato) rare earth analogues M(Pc) 2 and M[Pc(OC 8H 17) 8] 2.

The local atomic quasicrystal structure of the icosahedralMg25Y11Zn64 alloy

A local and medium range atomic structure model for the face centred icosahedral (fci)Mg25Y11Zn64 alloy has beenestablished in a sphere of r = 27 Å. The model was refined by least squares techniques using the atomic pair distribution(PDF) function obtained from synchrotron powder diffraction. Three hierarchies of theatomic arrangement can be found: (i) five types of local coordination polyhedra for thesingle atoms, four of which are of Frank–Kasper type. In turn, they (ii) form a three-shell(Bergman) cluster containing 104 atoms, which is condensed sharing its outer shell with itsneighbouring clusters, and (iii) a cluster connecting scheme corresponding to athree-dimensional tiling leaving space for a few glue atoms. Inside adjacent clusters,Y8 cubes are tilted with respect to each other and thus allow for overall icosahedralsymmetry. It is shown that the title compound is essentially isomorphicto its holmium analogue. Therefore, fci-Mg–Y–Zn can be seen as therepresentative structure type for the other rare earth analogues fci-Mg–Zn–RE(RE = Dy,Er, Ho, Tb) reported in the literature.

Nature of the Transition Metal−Cycloheptatrienyl Bond. Computational Studies of the Electronic Structure of [M(η7-C7H7)(η5-C5H5)] (M = groups 4−6)

The geometric and electronic structures of the title compounds are investigated using relativistic, gradient-corrected density functional theory. The metal−ligand bond lengths in the transactinide compounds are found to be generally larger than for the 3d, 4d, and 5d systems, suggesting that the actinide contraction is not significantly bigger than the lanthanide analogue. Excellent agreement is obtained between computed and experimental valence ionization energies. The localization properties of the key 1e2 electrons are analyzed and suggest that the cycloheptatrienyl ring functions more as a −3 ligand than as a +1 ligand in these mixed ring complexes. Comparisons are made with previous photoelectron spectroscopic determinations of the character of the 1e2 electrons. The metal−cycloheptatrienyl bonding energies are calculated and are found to be weakest for the transactinide molecules.

The distinct affinity of cyclopentadienyl ligands towards trivalent uranium over lanthanide ions. Evidence for cooperative ligation and back-bonding in the actinide complexes

The mono and bis(cyclopentadienyl) compounds [M(C5H4Bu t)I2] and [M(C5H4Bu t)2I](M = U, La, Ce, Nd) were formed in thf by comproportionation reactions of [M(C5H4Bu t)3] and LnI3 or [UI3(L)4](L = thf or py) in the molar ratio of 1 : 2 and 2 : 1, respectively, while treatment of [UI(3)(py)(4)] or LnI(3)(Ln = La, Ce, Nd) with 1 or 2 mol equivalents of LiC5H4Bu t in thf afforded the [M(C5H4Bu t)I2] and [M(C5H4Bu t)2I2]- compounds, respectively. The X-ray crystal structures of [M(C5H4Bu t)I2(py)3](M = U, La, Ce, Nd), [{Ce(C5H4Bu t)2(mu-I)}2] and [M(C5H4Bu t)2I(py)2](M = U, Nd) have been determined; the differences between the average M-C distances in the mono(cyclopentadienyl) complexes correspond to the variation in the ionic radii of the trivalent uranium and lanthanide ions while the U-N and U-I bond lengths seem to be smaller than those predicted from a purely ionic bonding model. The distinct affinity of the cyclopentadienyl ligands towards Ln(III) and U(III) was revealed by two series of competing reactions: the ligand exchange reactions between [Ln(C5H4Bu t)(n')I(3-n')](Ln = La, Ce, Nd) and [U(C5H4Bu t)(n'')I(3-n'')] species (1 < or = n'+n'' =n < or = 5), and the addition of n mol equivalents of LiC(5)H(4)Bu(t)(1 [less-than-or-equal]n[less-than-or-equal] 5) to a 1 : 1 mixture of LnI3 and [UI3(thf)4] or [UI3(py)4]. The stability of the [M(C5H4Bu t)I2] species was found to vary in the order Nd > Ce > U > La, a trend which is in accord with an electrostatic bonding model. However, the bis and tris(cyclopentadienyl) complexes of uranium are more stable than their lanthanide analogues. This difference can be accounted for by a higher degree of covalency in the U-C5H4Bu t bond, resulting from the late appearance of back-bonding which would emerge only after the first cyclopentadienyl ligand is bound.

A Comparison of Analogous 4f‐ and 5f‐Element Compounds: Syntheses, X‐ray Crystal Structures and Catalytic Activity of the Homoleptic Amidinate Complexes [M{MeC(NCy)2}3] (M = La, Nd or U)

AbstractReaction of UCl4 with [Li{RC(NCy)2}(THF)]2 (R = Me, 1a; R = nBu, 1b) in THF gave the tris(amidinate) compounds [U{RC(NCy)2}3Cl] (R = Me, 2a; R = nBu, 2b) which were reduced with lithium powder in THF to the homoleptic complexes [U{RC(NCy)2}3] (R = Me, 3a; R = nBu, 3b). Complexes 1a, 1b, 2a and 3a have been crystallographically characterized. Comparison of the crystal structure of 3a with those of the lanthanide analogues [Ln{MeC(NCy)2}3] (Ln = La, 4; Ln = Nd, 5; Ln = Yb, 6) shows that the average U−N distance is shorter than expected from a purely ionic bonding model. The uranium complex 3a is much less efficient than its lanthanide counterparts in the catalytic polymerization of ϵ‐caprolactone because of its rapid oxidation into UIV species. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004)

Vibrational spectroscopy of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes: (Part 10) The infrared and Raman characteristics of phthalocyanine in heteroleptic bis(phthalocyaninato) rare earth complexes with decreased molecular symmetry

The infrared (IR) spectroscopic data for a series of eleven heteroleptic bis(phthalocyaninato) rare earth complexes MIII(Pc)[Pc(α-OC5H11)4] (M = Sm–Lu, Y) [H2Pc = unsubstituted phthalocyanine, H2Pc(α-OC5H11)4 = 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine] have been collected with 2cm−1 resolution. Raman spectroscopic properties in the range of 500–1800cm−1 for these double-decker molecules have also been comparatively studied using laser excitation sources emitting at 632.8 and 785nm. Both the IR and Raman spectra for M(Pc)[Pc(α-OC5H11)4] are more complicated than those of homoleptic bis(phthalocyaninato) rare earth analogues due to the decreased molecular symmetry of these double-decker compounds, namely C4. For this series, the IR Pc− marker band appears as an intense absorption at 1309–1317cm−1, attributed to the pyrrole stretching. With laser excitation at 632.8nm, Raman vibrations derived from isoindole ring and aza stretchings in the range of 1300–1600cm−1 are selectively intensified. In contrast, when excited with laser radiation of 785nm, the ring radial vibrations of isoindole moieties and dihedral plane deformations between 500 and 1000cm−1 for M(Pc)[Pc(α-OC5H11)4] intensify to become the strongest scatterings. Both techniques reveal that the frequencies of pyrrole stretching, isoindole breathing, isoindole stretchings, aza stretchings and coupling of pyrrole and aza stretchings depend on the rare earth ionic size, shifting to higher energy along with the lanthanide contraction due to the increased ring-ring interaction across the series. The assignments of the vibrational bands for these compounds have been made and discussed in relation to other unsubstituted and substituted bis(phthalocyaninato) rare earth analogues, such as M(Pc)2 and M(OOPc)2 [H2OOPc = 2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyanine].

Comparative Electrochemical Study of Unsubstituted and Substituted Bis(phthalocyaninato) Rare Earth(III) Complexes

AbstractThe electrochemistry of homoleptic substituted phthalocyaninato rare earth double‐decker complexes M(TBPc)2and M(OOPc)2[M = Y, La...Lu except Pm; H2TBPc = 3(4),12(13),21(22),30(31)‐tetra‐tert‐butylphthalocyanine, H2OOPc = 3,4,12,13,21,22,30,31‐octakis(octyloxy)phthalocyanine] has been comparatively studied by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in CH2Cl2containing 0.1Mtetra‐n‐butylammonium perchlorate (TBAP). Two quasi‐reversible one‐electron oxidations and three or four quasi‐reversible one‐electron reductions have been revealed for these neutral double‐deckers of two series of substituted complexes, respectively. For comparison, unsubstituted bis(phthalocyaninato) rare earth analogues M(Pc)2(M = Y, La...Lu except Pm; H2Pc = phthalocyanine) have also been electrochemically investigated. Two quasi‐reversible one‐electron oxidations and up to five quasi‐reversible one‐electron reductions have been revealed for these neutral double‐decker compounds. The three bis(phthalocyaninato)cerium compounds display one cerium‐centered redox wave between the first ligand‐based oxidation and reduction. The half‐wave potentials of the first and second oxidations and first reduction for double‐deckers of the tervalent rare earths depend on the size of the metal center. The difference between the redox potentials of the second and third reductions for MIII(Pc)2, which represents the potential difference between the first oxidation and first reduction of [MIII(Pc)2]−, lies in the range 1.08−1.37 V and also gradually diminishes along with the lanthanide contraction, indicating enhanced π−π interactions in the double‐deckers connected by the smaller, lanthanides. This corresponds well with the red‐shift of the lowest energy band observed in the electronic absorption spectra of reduced double‐decker [MIII(Pc′)2]−(Pc′ = Pc, TBPc, OOPc). (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2004)

Preparation of a series of mesoporous lanthanide oxides by a neutral supramolecular templating routeElectronic supplementary information (ESI) available: DSC results. See http://www.rsc.org/suppdata/jm/b3/b313982d/

In this study, data are provided that detail the first preparation of high surface area and structurally ordered mesoporous lanthanide oxides by a neutral surfactant supramolecular templating route. For the first time, retention of mesoporosity in lanthanide oxides (other than those of cerium) after surfactant removal by simple air calcination at temperatures to 450 °C is demonstrated. The as-prepared lanthanide–surfactant composites displayed long range ordering of the mesoporous phase and although significant amounts of order can be lost, the materials exhibit a large degree of porosity, high surface area and some ordering of the pore array after high temperature calcination. In the case of lanthanum oxide, a mesoporous material displaying a cubic structured array of pores was obtained. The heavier lanthanide analogues readily formed lamellar phases. Removal of water and surfactant from between lamellae was found to result in some collapse of the as-prepared porous structures although in all cases mesoporosity was still evident. Ytterbium was found to exhibit more complex behaviour with a cubic phase being generated. This material was also found to display reduced periodicity of the pore structure on calcination and all materials retained highly textured surfaces after the thermal treatment to remove surfactant.

The behaviour of the rare earths during the precipitation of sodium, potassium and lead jarosites

The behaviour of the rare earths during the precipitation of sodium, potassium and lead jarosites from both sulphate and chloride media was investigated. Efforts to synthesize the end-member rare earth analogues of sodium jarosite and potassium jarosite were unsuccessful. The precipitation of sodium jarosite or potassium jarosite in the presence of various concentrations of the rare earths resulted in the incorporation of <0.3 wt.% of the rare earths in the jarosite structure. Comparable levels of rare earth incorporation were noted in both sodium jarosite and potassium jarosite. Increasing solution pH or increasing ferric ion concentration resulted in higher precipitate yields, but had only a minimal effect on the structural incorporation of the rare earths in the jarosite. Sodium jarosite and potassium jarosite precipitated from predominantly chloride media had levels of rare earth incorporation comparable to those of the jarosites made from sulphate solutions. Lead jarosite precipitated from rare earth-containing solutions incorporated <0.2 wt.% of the rare earths. SEM studies showed that the presence of the rare earths had little effect on the morphology of the precipitated sodium, potassium and lead jarosites. Clearly, the trivalent rare earth (RE) elements do not substitute extensively for trivalent iron in the jarosite structure, and this behaviour likely reflects the larger size, different co-ordination and the significantly lower hydrolyzability of the trivalent rare earth ions relative to ferric ions.

Infrared spectra of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes. Part 3. The effects of substituents and molecular symmetry on the infrared characteristics of phthalocyanine in bis(phthalocyaninato) rare earth complexes

The infra-red (IR) spectroscopic data for a series of 45 homoleptic unsubstituted and substituted bis(phthalocyaninato) rare earth complexes M(Pc) 2 and M(Pc*) 2 [M=Y, La…Lu except Pm; H 2Pc=phthalocyanine; H 2Pc*=2,3,9,10,16,17,24,25-octakis(octyloxy)phthalocyanine (H 2OOPc) and 2(3),9(10),16(17),24(25)-tetra( tert-butyl)phthalocyanine (H 2TBPc)] have been collected with resolution of 2 cm −1. The IR spectra for M(Pc) 2 and M(OOPc) 2 are much simpler than those of M(TBPc) 2, revealing the relatively higher symmetry of the former two compounds. For M(Pc) 2 the Pc − marker band at 1312–1323 cm −1, attributed to the pyrrole stretching, and the isoindole stretching band at 1439–1454 cm −1 are found to be dependent on the central rare earth size, shifting slightly to the higher energy along with the decrease of rare earth radius. The frequency of the vibration at 876–887 cm −1 is also dependent on the rare earth ionic size. The metal size-sensitivity of this band and theoretical studies render it possible to re-assign it to the coupling of isoindole deformation and aza vibration. The nature of another metal-sensitive vibration mode at 1110–1116 cm −1, which was previously assigned to the CH bending, is now re-assigned as an isoindole breathing mode with some small contribution also from CH in-plane bending. These assignments are supported by comparative studies of the IR spectra of substituted bis(phthalocyaninato) analogues M(OOPc) 2 and M(TBPc) 2. By comparison between the IR spectra of unsubstituted and substituted bis(phthalocyaninato) rare earth analogues and according to the IR characteristics of alkyl groups, some characteristic vibrational fundamentals due to the Pc rings and the substituents can be separately identified. In conclusion, all the metal size-dependent IR absorptions are composed primarily of the vibrations of pyrrole or isoindole stretching, breathing or deformation or aza stretching of the Pc ring.

Infrared spectra of phthalocyanine and naphthalocyanine in sandwich-type (na)phthalocyaninato and porphyrinato rare earth complexes: Part 4. The infrared characteristics of phthalocyanine in heteroleptic tris(phthalocyaninato) rare earth complexes

The infrared (IR) spectroscopic data for a series of heteroleptic tris(phthalocyaninato) rare earth complexes (Pc)M(OOPc)M(OOPc) (M=Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu, Y) and (Pc)Tm(OOPc)Tm(Pc) [H 2Pc=unsubstituted phthalocyanine, H 2OOPc=2,3,9,10,16,17,24,25-octakis(octyloxy)phthalocyanine] have been collected with 2 cm −1 resolution. The IR spectra for (Pc)M(OOPc)M(OOPc) are more complicated than those of bis(phthalocyaninato) rare earth analogues, revealing the relatively lower symmetry of these triple-decker compounds. For both types of heteroleptic tris(phthalocyaninato) rare earth compounds, the characteristic phthalocyanine dianion IR bands for both Pc 2− and OOPc 2−at ca. 1329 and 1380 cm −1 attributed, respectively, to the pyrrole stretching and the symmetric CH bendings of CH 3 groups in octyloxy side chains of OOPc rings together with contribution from the isoindole stretching vibrations are observed in these spectra. The frequencies of the vibration at 1312–1318, attributed to pyrrole stretchings, are dependent on the central rare earth size, shifting slightly to higher energy along with the decrease of rare earth radius across the series. The decreased sensitivity of the frequency of the vibration at 1463–1465 cm −1 and rare earth metal size compared with that of the corresponding isoindole stretching band at 1439–1454 cm −1 for bis(phthalocyaninato) rare earth counterparts indicates that the π–π interactions in these heteroleptic triple-deckers are weaker than those in the double-deckers.

Crystal structure and magnetic properties of the UFe 7Al 5 uranium–iron aluminide

The ternary compound UFe 7Al 5 was synthesized by arc melting, followed by annealing at 850°C. The crystal structure was determined by single-crystal X-ray diffraction and refined to a residual value of R=0.039 ( S=1.030), with lattice parameters a=8.581(2) Å and c=4.946(1) Å. This compound is a new extreme composition in the family of intermetallics with general formula UFe x Al 12− x crystallizing in the tetragonal ThMn 12-type structure, space group I4 /mmm. In contrast to UFe x Al 12− x within the composition range 4⩽ x⩽6, in UFe 7Al 5 the additional iron atom is found in the 8 i equipositions. Magnetization measurements versus temperature show two magnetic transitions at 363 and 275 K, respectively, with a ferromagnetic behavior below the highest temperature transition. 57Fe Mössbauer data indicate that the high-temperature transition is related to the ordering of the iron atoms. The dependence of the isomer shifts and magnetic hyperfine fields on the crystallographic site and on the number of the iron nearest neighbors is similar to that observed in the other UFe x Al 12− x and rare-earth analogues. The magnetic hyperfine field values of iron atoms on 8 i sites is larger than in the other sites, in agreement with previous data obtained for other ThMn 12-type compounds.

Synthesis, structure, and olefin polymerization catalysis of a novel vanadium(III) 1,1?-bi-2-naphtholate complex

The reaction of VCl 3 with (S)-(-)-Na 2 (binol) (binol = 1,1'-bi-2-naphtholate) gave a new vanadium(III) complex, [Na(OEt 2 )] 3 [V(binol) 3 ] (Fig. 1). The X-ray crystallographic structure of this complex (Complex 1) in Figure 1 reveals its propeller-like structure, which is similar to those of the reported rare earth analogues. The complex showed moderate catalytic activities for ethylene polymerization upon activation with modified methylaluminoxane (MMAO) and with diethyl-aluminum chloride (DEAC). The Complex 1/DEAC system also catalyzed the polymerization of propylene to give atactic polypropylene with low activity.

Synthesis and structure of a chromium(III) complex coordinated by 1,1′-Bi-2-naphtholate ligands and its catalytic activity for ethylene polymerization

Reaction of CrCl 3(THF) 3 with rac-Li 2(binol) (binol=1,1′-bi-2-naphtholate) gave a new chromium(III) complex, [Li(THF)] 3[Cr(binol) 3]·3(toluene) ( 1). The X-ray crystallographic structure of 1 revealed its propeller-like structure similar to those of the reported rare earth analogues. The complex 1 showed moderate catalytic activities for ethylene polymerization upon activation with modified methylaluminoxane (MMAO) and with diethylaluminum chloride. When 1 was supported on the silica surface, activity increased to two times of homogeneous 1/MMAO system.

Structural study of metal–hydrogen interactions in cubic PrH 2+ x and rare-earth analogues

Neutron diffraction data on cubic PrD 2.92 show that the deuterium atoms in the octahedral interstices are displaced by 0.31 Å from the centre towards the faces. This leads to a considerable shortening of the Pr–D bonds (2.57 Å as compared to 2.74 Å for the centre position) and thus to a gain of energy. A comparison with other cubic RD 2+ x structures (R=La, Ce, Nd) shows that the displacements and the shortening of the R–D bonds decrease as the atomic size of R decreases, whereas the shortest contact distances between the deuterium atoms in octahedral and tetrahedral interstices remain nearly constant (∼2.1 Å). These findings suggest that as one goes from light to heavy R elements (or from low to high hydrogen contents) the energy gain due to R–H bond shortening (or the addition of new R–H bonds) is increasingly offset by the energy loss due to repulsive H–H interactions. This trend is consistent with the decreased homogeneity range of the cubic RH 2+ x phase and the appearance of the trigonal RH 3 phase in R–H systems containing heavy R elements.

Probing the reactivity of the radiation sensitizer motexafin gadolinium (Xcytrin®) and a series of lanthanide(III) analogues in the presence of both hydroxyl radicals and aqueous electrons

The competition of the radiation sensitizer motexafin gadolinium (Xcytrin®, gadolinium(III) texaphyrin) and several other water-soluble metallotexaphyrin complexes with N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) for solvated electrons and hydroxyl radicals was studied using pulse radiolysis and by steady-state γ-radiolysis. It was found that the one-electron reduced forms ( M - Tex ·+) of the Gd(III) , Eu(III) , Dy(III) , Yb(III) , and Cd(II) texaphyrin complexes, after an initial reaction with hydrated electrons, do not compete with TMPD for hydroxyl radicals formed under pulse radiolytic conditions. By contrast, the reduced Y(III) , In(III) , Tm(III) , and Lu(III) texaphyrin complexes do. These differences in competitive reactivity toward . OH are rationalized in terms of the relative rates of protonation of the various singly reduced texaphyrins. In the case of Gd - Tex 2+ in particular, the one-electron reduced product, Gd - Tex ·+, protonates rapidly, producing a redox-inactive species that does not react appreciably with . OH . By contrast, the one-electron reduced product from, e.g., Lu - Tex 2+ (motexafin lutetium), does. These results may explain, at least in part, why the Gd(III) texaphyrin functions as a radiation sensitizer in vivo, while the analogous Lu(III) complex does not.

High-Yield Synthesis and Single-Crystal X-ray Structure of a Plutonium(III) Aquo Complex: [Pu(H2O)9][CF3SO3]3

The aquo complex of Pu(III) is 9-coordinate with an ideal tricapped trigonal-prismatic geometry. The cation was crystallized as the triflate salt in quantitative yield from dissolution of Pu metal in triflic acid. Structural comparisons with analogous lanthanide aquo complexes are presented.