Lanthanide Chemistry Research Articles

Cyclopentadienyl Yttrium Ene-Diamido Complexes: Coupling of the Ene-Diamido Ligand with Isocyanate

The yttrium ene-diamido complexes supported by Cp (C5H5) and Cp* (C5Me5) ligands have been synthesized and characterized. The reactions of the Cp* derivative with the isocyanate ArNCO (Ar = 2,6-iPr2C6H3) led to the C–C coupling of the ene-diamido ligand with ArNCO, while reaction of the Cp derivative resulted in not only the same C–C coupling but also the C–N coupling of the C–C coupling product with another molecule of ArNCO, demonstrating the unique reactivity of ene-diamido ligands in rare-earth chemistry. The products have been characterized by X-ray single-crystal analysis.

Tephrochronology of the Manzanita Limestone in the Middle Permian (Guadalupian) Type Area, West Texas and southeastern New Mexico, USA

Despite being recognized for many years, bentonites in the Guadalupian (Middle Permian Series) type area of West Texas and southeastern New Mexico have received little research attention. These important deposits offer opportunities for long distance stratigraphic correlation and high-precision radioisotopic age dating. In this study, apatite phenocryst chemistry is used to establish a tephrochronologic framework for the Manzanita Limestone Member of the Cherry Canyon Formation. Samples were collected from bentonites in one core and five field localities including Nipple Hill, which is the site of the Late Guadalupian (Capitanian Stage) GSSP and located in Guadalupe Mountains National Park. Apatite phenocrysts from these samples were analyzed for minor, trace, and rare earth element chemistry using electron microprobe techniques. Results indicate the presence of three patterns or trends of data that are repeated at multiple localities. These groups of data are interpreted to represent coeval deposits and are correlated among several localities to form a tephrochronologic framework. This framework links the strata on Nipple Hill with that of several other Guadalupian type area localities. Absolute age time control for the Guadalupian is poor, and the precise stratigraphic position of the existing radioisotopic date from Nipple Hill is uncertain. Based on a review of published reports and a new measured section of Nipple Hill presented herein, the most accurate position is in the Manzanita Member. That placement adjusts the only radioisotopic age constraint for the Capitanian GSSP lower in the Wordian Stage than previously reported. The bentonite correlations proposed herein constrain this position to the Mz-3 cycle of the Manzanita High Frequency Sequence and allow it to be traced to several outcrop localities, and across the Delaware Basin in the subsurface. Based on the correlation of a bentonite from its locus typicus near Casey’s Last Chance Well in Culberson County, Texas, the type specimen of the biostratigraphically significant ammonoid Newellites richardsoni is confirmed to have been recovered from the basal Manzanita Member (Wordian Stage), stratigraphically underlying the radioisotopic age date. The type locality of this ammonoid has been inconsistently reported in museum records and in the literature.

Age and significance of felsic dikes from the UHP western gneiss region

Twenty-one plagioclase-bearing dikes were analyzed to place firmer limits on the end of (ultra)high-pressure (UHP) metamorphism across the Western Gneiss Region (WGR). Nineteen dikes were analyzed with laser ablation split-stream petrochronology to tie the U-Pb dates to zircon rare earth element (REE) chemistry, and a few key samples were analyzed by chemical abrasion thermal ionization mass spectrometry to provide high-precision constraints. All analyzed dikes yielded zircons with REE chemistry consistent with low-pressure crystallization. Approximately half of the dikes yield Precambrian dates; nondeformed dikes of this age support previous interpretations that much of the WGR underwent limited deformation during Caledonian subduction and exhumation. The oldest Caledonian dikes have dates that overlap with the circa 420–400 Ma eclogite dates from the region; this discrepancy indicates that either (1) cryptic structures separate early exhumed material from later exhumed material, (2) some of the dike dates are not low-pressure crystallization ages, or (3) post-406 Ma dates from eclogites are posteclogite-facies retrogression ages.

Dinuclear, tetrakis(acetato)-bridged lanthanide(III) complexes from the use of 2-acetylpyridine hydrazone

The first employment of 2-acetylpyridine hydrazone in lanthanide(III) chemistry has led to dinuclear complexes with four bridging acetate groups of two different types and chelating 2-acetylpyridine hydrazone ligands.

Laudatio for professor Dr. Hab. Rajmund S. Dybczyński Hevesy Medal Awardee 2013

Rajmund Stanislaw Dybczynski was born in Warsaw, Poland in 1933. He received his MSc in chemistry from Warsaw University in 1955. He spent 2 years in the Institute of General Chemistry, Warsaw, where he got interested in the theory and practice of ion exchange and worked on physico-chemical methods for characterization of ion exchange resins. In 1957 he joined the Institute of Nuclear Research in Warsaw where he received his PhD in 1963 and DSc in 1971. In 1987, the President of Poland conferred the title of ‘‘Professor in Chemistry’’ upon him. Prof. Dybczynski was the Head of Laboratory for Radiometric Methods of Analysis since 1965, and became the Head of Department of Analytical Chemistry at the Institute of Nuclear Chemistry and Technology (INCT) in Warsaw in 1995 and continued until 2008. He was in charge of the Analytical Quality Control Services section at the IAEA Seibersdorf Laboratory during 1975–1980. His early work was focused on the use of radioactive tracers for studying the thermodynamics of ion exchange reactions, effect of resin cross-linking and of temperature on chromatographic separations and development of schemes for group and individual separation of radionuclides including inter alia rare earth elements (REE). Prof. Dybczynski’s interest in REE chemistry stood the test of time and even in recent years he published several papers on REE separation and determination by NAA, ICP-MS, ion chromatography (IC) and RP-HPLC. Professor Dybczynski has made significant contributions in radiochemical neutron activation analysis by developing a number of new separation methods based on ion exchange and extraction chromatography. He applied his instrumental and radiochemical NAA methods to study environmental pollution through the analysis of air filters, human hair and coal fly ash, to determine impurities in some noble metals, to identify single human hairs for forensic purposes, and to investigate possible correlation between coronary heart disease and levels of certain trace elements such as Cu and Zn, among other projects. INAA, RNAA and non-nuclear methods of inorganic trace analysis were used with success to establish genetic relationship between Baszkowka meteorite that fell in Poland in 1994 and another chondrite Mount Tazerzait which fell in Niger, Africa 3 years earlier. Professor Dybczynski has been interested in QA/QC for a long time and was involved in preparation and certification of CRMs for inorganic trace analysis at IAEA. He developed the approach to evaluate data obtained through interlaboratory comparison and to assign certified and information values. His procedure is sometimes referred to as Dybczynski’s method in the literature and has been adapted by IAEA and some laboratories in Poland, Canada and former Czechoslovakia. Professor Dybczynski initiated the developmental work on highly accurate (definitive) methods for the determination of selected elements by radiochemical NAA. He also developed guidelines to obtain data with high accuracy. He demonstrated that the definitive methods can meet the requirements of a ratio primary reference measurement procedure (RPRMP). He developed definitive methods for As, Cd, Co, Cu, Fe, Mo, Ni, Se, and U and applied them to validate other methods and to help in the certification of 10 candidate CRMs, prepared and issued by INCT. Professor Dybczynski is the author and co-author of over 200 papers published in internationally reputed journals, 5 monographs, A. Chatt (&) Department of Chemistry, Trace Analysis Research Centre, Dalhousie University, 6274 Coburg Road, Room 212, P.O. Box 15000, Halifax, NS B3H 4R2, Canada e-mail: chatt@dal.ca

Rare earth elements in the sediments of Lake Baikal

Lake Baikal is the deepest and probably oldest lake on Earth. Its water column is pervasively oxic and sedimentation rates are very low which leads to the formation of a dynamic iron (Fe) and manganese (Mn) enrichment below the Mn(II)/O2 boundary. These often massive accumulations can be buried within the reducing part of the sediments and give rise to complex and cryptic redox cycles. The mobility of rare earth elements (REEs) is influenced by the dissolution and reduction dynamics of the ferromanganese oxides. The present study offers an overview of the REE chemistry in Lake Baikal and its catchment area and more specifically REE distribution in five 11- to 26-cm-long sediment cores situated across the lake at different water depths. We analysed and discussed normalised REE patterns and their consequential cerium (Ce) anomalies. While particulate REE concentrations are mainly influenced by processes above or near the surface of Lake Baikal, such as the development of a widespread negative Ce anomaly, processes occurring during early diagenesis in the sediment are most reflected in pore water REEs. The dissolution of ferromanganese oxides at the Mn(II)/O2 boundary remobilizes significant amounts of REE into the pore water whereby some are likely adsorbed onto colloidal Fe oxides. However, besides the tendency of Ce being associated with Mn-oxides, pore water REEs fractionate predominantly around the buried Fe/Mn accumulation where light REEs preferentially adsorb onto Fe-oxides.

Fluorite REE-Y (REY) geochemistry of the ca. 850 Ma Tumen molybdenite–fluorite deposit, eastern Qinling, China: Constraints on ore genesis

The Tumen molybdenite–fluorite vein system is hosted by carbonate rocks of the Neoproterozoic Luanchuan Group, located on the southern margin of the North China Craton (NCC) in central China. Previous studies divided the mineralization into four stages according to the crosscutting relationships between veinlets and their mineral assemblages. In this contribution, two distinctive types of fluorite mineralization are recognized: 1) the first type (Type 1) includes colourless, white or green fluorite grains present in Stage 1 veins; and 2) the second type includes Type 2a purple fluorite present in Stage 2 veins and does not coexist with sulfides, and Type 2b purple fluorite crystals associated with sulfides in Stage 2 veins. The rare earth element (REE) content in the fluorite ranges between 13.8 and 27.9ppm in Type 1, 16.9 and 27.2ppm in Type 2a, and 42.5 and 75.1ppm in Type 2b, which suggests that the fluorite was precipitated from acidic fluids (given that REEs are mobile in saline HCl-bearing fluids at high temperature (~400°C)). Comparing the REE chemistry of the Stage 1 against Stage 2 fluorite, the LREE/HREE ratios decrease from 9.8 to 4.0, La/Yb ratios decrease from 16.0 to 6.9 and La/Ho ratios decrease from 10.2 to 3.0, indicating that the hydrothermal process was at high-T and low-pH conditions. The Eu/Eu* ratios in the fluorite decrease from 1.11±0.35 for Type 1 through 0.89±0.19 for Type 2a to 0.75±0.17 for Type 2b, suggesting a gradual increase in oxygen fugacity (fO2) and pH of the mineralising fluid. The Tb/Ca, Tb/La and Y/Ho ratios of the fluorite types indicate that they were formed from the interaction between magmatic fluids and carbonate wallrocks. The fluorite samples show similar REE+Y (REY) patterns to those of dolostone units in the Luanchuan Group and the nearby Neoproterozoic syenite, suggesting that the REY in the fluorite was mainly sourced from the host-rocks, although the syenite could be an additional minor source.

Contrast agents for MRI: 30+ years and where are we going?

Thirty years ago, Schering filed the first patent application for a contrast agent for magnetic resonance imaging (MRI) covering the forefather of the gadolinium contrast agents and still the most widely used gadolinium probe: gadolinium(III) diethylenetriaminepentaacetate (Magnevist). To date, 11 contrast agents have been approved by the US Food and Drug Administration for intravenous use. Coordination chemists have done a great deal to move the field forward. Our understanding of lanthanide chemistry now makes possible the design of complexes with long rotational correlation times, fast or slow water-exchange rates, high thermodynamic stabilities, and kinetic inertness, leading to sensitive and nontoxic contrast agents. Chemists did not stop there. The last few decades has seen the development of novel classes of probes that yield contrast through different mechanisms, such as paramagnetic chemical exchange saturation transfer agents. Thirty years since the first patent, chemists are still leading the way. The development of high-sensitivity contrast agents for high magnetic fields, safe probes for patients with kidney disorders, and multimodal, targeted, and responsive agents demonstrates that the field of contrast agents for MRI still has much to offer.

Sr, Nd, Pb and Os Isotope Systematics of CAMP Tholeiites from Eastern North America (ENA): Evidence of a Subduction-enriched Mantle Source

The Central Atlantic Magmatic Province (CAMP) is one of the largest igneous provinces on Earth, with an areal extent exceeding 10e7km2. Here we document the geochemical characteristics of CAMP basalts from Triassic-Jurassic basins in northeastern USA and Nova Scotia (Canada). The CAMP rocks occur as lava flows, sills and dykes. All of our analysed samples show chemical characteristics typical of CAMP basalts with low titanium content, which include enrichment in the most incompatible elements and negative Nb anomalies. All the basalts also show enriched Sr-Nd-Pb initial (t=201Ma) isotopic compositions (206Pb/204Pbini. = 18·155-18·691, 207Pb/204Pbini. = 15·616-15·668, 208Pb/204Pbini. = 38·160-38·616, 143Nd/144Ndini. = 0·512169-0·512499). On the basis of stratigraphy, rare earth element (REE) chemistry and Sr-Nd-Pb isotope composition, three chemical groups are defined. The Hook Mountain group, with the lowest La/Yb ratios, initial 206Pb/204Pbini. >18·5 and 143Nd/144Ndini.>0·51238, comprises all the latest and upper stratigraphic units. The Preakness group, with intermediate La/Yb ratios, 206Pb/204Pbini.>18·5 and 0·51233>143Nd/144Ndini.>0·51225, comprises the intermediate units. The Orange Mountain group has the highest La/Yb ratios and 143Nd/144Ndini.<0·51235 and involves all the earliest and stratigraphically lowest units, including the entire North Mountain basalts from Nova Scotia. In this last group, three sub-groups may be distinguished: the Rapidan sill, which has 206Pb/204Pbini. higher than 18·5, the Shelburne sub-group, which has 143Nd/144Ndini.<0·51225, and the remaining Orange Mt samples. With the exception of one sample, the Eastern North America (ENA) CAMP basalts display initial 187Os/188Os ratios in the range of mantle-derived magmas (<0·15). Simple modelling shows that the composition of the ENA CAMP basalts cannot plausibly be explained solely by crustal contamination of oceanic island basalt (OIB), mid-ocean ridge basalt (MORB) or oceanic plateau basalt (OPB) magmas. Mixing of such magma compositions with sub- continental lithospheric mantle (SCLM)-derived melts followed by crustal contamination, by either assimilation-fractional crystallization (AFC) or assimilation through turbulent ascent (ATA) pro- cesses is somewhat more successful. However, this latter scenario does not reproduce the REE and isotopic composition of the ENA CAMP in a fully satisfactory manner. Alternatively, we propose a model in which asthenospheric mantle overlying a subducted slab (i.e. mantle wedge) was enriched during Cambrian to Devonian subduction by sedimentary material, isotopically equivalent to Proterozoic-Lower Paleozoic crustal rocks. Subsequently, after subduction ceased, the isotopic composition of this mantle evolved by radioactive decay for another 170 Myr until the CAMP magmatic event. Varying amounts and compositions of the incorporated sedimentary component coupled with radiogenic ingrowth over time can account for the main geochemical characteristics of the ENA CAMP (enriched incompatible element patterns, negative Nb anomalies, enriched Sr-Nd-Pb isotopic composition) and the differences between the three chemical groups.

The coordination chemistry of trivalent lanthanides (Ce, Nd, Sm, Eu, Gd, Dy, Yb) with diphenyldithiophosphinate anions

Understanding the coordination chemistry between lanthanide elements and dithiophosphinate ligands is important given prospects for using dithiophosphinate ligands to separate trivalent minor actinides from lanthanides in advanced nuclear fuel cycles. Reported here is the coordination chemistry of a series of lanthanide elements (Ce, Nd, Sm, Eu, Gd, Dy, and Yb) with diphenyldithiophosphinate anions, S2PPh21−. In all cases, LnCl3 was reacted with 4 equivalents of S2PPh21−. The large lanthanides (Ce3+, Nd3+, Sm3+, Eu3+) formed eight coordinate anions of the general formula Ln(S2PPh2)41− and were characterized by 1H and 31P NMR, IR, UV–Vis, elemental analysis, and single crystal X-ray crystallography. For the slightly smaller Gd3+ and Dy3+ ions, a break in reactivity was observed. Here, analyses of reaction solutions by 1H and 31P NMR spectroscopy suggested that a complicated mixture formed from which single crystals of eight coordinate and neutral Gd(S2PPh2)3(NCMe)2 and Dy(S2PPh2)3(NCMe)2 complexes were isolated. Reactions involving even smaller Yb3+ ions provided similar results to Gd3+ and Dy3+, in that reaction solutions also contained a mixture of products. In the Yb3+ case a new heteroleptic species [Ph4P][Yb(S2PPh2)3Cl], was isolated in single crystal form. The structural data have been presented in comparison to that of [Ph4P][Sm(S2PMe2)4] and [Ph4P][Eu(S2PMe2)4], which were also structurally characterized for the first time. Overall, these results demonstrate how subtle differences in lanthanide ionic radii can drastically affect the coordination number, ligand stoichiometry, and charge on the resulting diphenyldithiophosphinate complex.

Provenance and tectonic setting of the metapelites deposits in the Bulfat Complex, NE-Iraq

Major and trace elements including rare earth elements (REEs) chemistry of the metapelitic rocks of Bulfat Complex (Iraqi Zagros Suture Zone) indicate their enrichment in large-ion Lithophile, light rare earth (LREE) elements, and relative depletion of high field strength and heavy rare earth (HREE) elements. The linear correlation coefficients between TiO2, K2O, and Al2O3 and total REE reveal that phyllosilicates (e.g., mica) and accessory minerals mainly Ti-bearing phases (e.g., ilmenite) are likely the dominant hosts for REEs. Chondrite-normalized REE patterns typical of continental margin settings with significant enrichment of LREE, prominent negative Eu anomalies, and nearly flat HREE are positively correlated with post-Archean Australian shale (PAAS) and upper continental crust (UCC) patterns. Additionally, their consistent elemental La/Sc, Th/Sc, La/Co, Th/Co, Cr/Th, and Eu/Eu* values suggest that sediments may have been originally derived from an old post-Archean upper continental crust composed chiefly of granitic component. It seems most likely that the felsic source rocks were originated by a process of intra-crustal differentiation such as partial melting and/or fractional crystallization involving fractionation of Ca-plagioclase. The geochemical evidences particularly REEs evaluation show that deposition of clasts occurred in an active continental margin setting during lower–upper Cretaceous period contemporaneous with the igneous activities. It is evident therefore that the clasts source is from the north–northeast side, i.e., from the active margin of Iranian microcontinent (Sanandaj–Sirjan Zone).

ChemInform Abstract: Lanthanide Amidinates and Guanidinates in Catalysis and Materials Science: A Continuing Success Story

AbstractReview: 72 refs.

Synthesis and Characterization of Paramagnetic Lanthanide Benzyl Complexes

The organometallic chemistry of paramagnetic lanthanides (Ln, from Ce to Yb) is far less developed compared to that of their diamagnetic counterparts (Sc, Y, La, and Lu). Lack of available starting materials and characterization methods are the major obstacles. Herein we report the synthesis and characterization of trisbenzyl complexes of neodymium, gadolinium, holmium, and erbium. In addition, we introduce a direct procedure for the synthesis of lanthanide benzyl and iodide complexes supported by a ferrocene diamide ligand starting from the corresponding oxides. All newly synthesized compounds were characterized by X-ray crystallography, 1H NMR spectroscopy (except for gadolinium compounds, which were NMR silent), and elemental analysis.

ChemInform Abstract: Beyond Samarium Diiodide: Vistas in Reductive Chemistry Mediated by Lanthanides(II)

AbstractReview: 285 refs.

Periodic Behavior of Lanthanide Coordination within Reverse Micelles

Trends in lanthanide(III) (Ln(III)) coordination were investigated within nanoconfined solvation environments. Ln(III) ions were incorporated into the cores of reverse micelles (RMs) formed with malonamide amphiphiles in n-heptane by contact with aqueous phases containing nitrate and Ln(III); both insert into pre-organized RM units built up of DMDOHEMA (N,N'-dimethyl-N,N'-dioctylhexylethoxymalonamide) that are either relatively large and hydrated or small and dry, depending on whether the organic phase is acidic or neutral, respectively. Structural aspects of the Ln(III) complex formation and the RM morphology were obtained by use of XAS (X-ray absorption spectroscopy) and SAXS (small-angle X-ray scattering). The Ln(III) coordination environments were determined through use of L(3)-edge XANES (X-ray absorption near edge structure) and EXAFS (extended X-ray absorption fine structure), which provide metrical insights into the chemistry across the period. Hydration numbers for the Eu species were measured using TRLIFS (time-resolved laser-induced fluorescence spectroscopy). The picture that emerges from a system-wide perspective of the Ln-O interatomic distances and number of coordinating oxygen atoms for the extracted complexes of Ln(III) in the first half of the series (i.e., Nd, Eu) is that they are different from those in the second half of the series (i.e., Tb, Yb): the number of coordinating oxygen atoms decrease from 9O for early lanthanides to 8O for the late ones--a trend that is consistent with the effect of the lanthanide contraction. The environment within the RM, altered by either the presence or absence of acid, also had a pronounced influence on the nitrate coordination mode; for example, the larger, more hydrated, acidic RM core favors monodentate coordination, whereas the small, dry, neutral core favors bidentate coordination to Ln(III). These findings show that the coordination chemistry of lanthanides within nanoconfined environments is neither equivalent to the solid nor bulk solution behaviors. Herein we address atomic- and mesoscale phenomena in the under-explored field of lanthanide coordination and periodic behavior within RMs, providing a consilience of fundamental insights into the chemistry of growing importance in technologies as diverse as nanosynthesis and separations science.

Electroanalytical chemistry of lanthanides and actinides

Electroanalytical chemistry of lanthanides and actinides

Geochemistry and Origin of Banded Iron-Formation from the Granulitic Terrain of North Arcot District, Tamil Nadu, South India

Banded iron formations (BIF) form an important part of the Archean supracrustal belts of South India. Major, trace and rare earth elements (REE) chemistry of the banded iron formation of Kavuthimalai-Vediyappanmalai area, North Arcot district, Tamil Nadu region are utilized to compare with other world BIF and explore that this a separate type of Tamil Nadu type. The petrographic observation and the study of REE indicates that this BIF are derived from mantle through hydrothermal solutions and fumarolic activity in submarine conditions with an age of approximately 3800 m.y. old.

ChemInform Abstract: Rare‐Earth Dialkyl and Dihydride Complexes Bearing Monoanionic Ancillary Ligands

AbstractReview: 65 refs.

Synthesis and Evaluation of Conformationally Restricted N4-Tetradentate Ligands for Implementation in An(III)/Ln(III) Separations

The previous literature demonstrates that donor atoms softer than oxygen are effective for separating trivalent lanthanides (Ln(III)) from trivalent actinides (An(III)) (Nash, K.L., in: Gschneider, K.A. Jr., et al. (eds.) Handbook on the Physics and Chemistry of Rare Earths, vol. 18—Lanthanides/Actinides Chemistry, pp. 197–238. Elsevier Science, Amsterdam, 1994). It has also been shown that ligands that “restrict” their donor groups in a favorable geometry, appropriate to the steric demands of the cation, have an increased binding affinity. A series of tetradentate nitrogen containing ligands have been synthesized with increased steric “limits”. The pKa values for these ligands have been determined using potentiometric titration methods and the formation of the colored copper(II) complex has been used as a method to determine ligand partitioning between the organic and aqueous phases. The results for the 2-methylpyridyl-substituted amine ligands are encouraging, but the results for the 2-methylpyridyl-substituted diimines indicate that these ligands are unsuitable for implementation in a solvent extraction system due to hydrolysis.

Multielectron redox chemistry of lanthanide Schiff-base complexes

We have developed a new way to introduce redox events at lanthanide centers which should lead to further expansion of the reductive chemistry of lanthanides.