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Byline: Robert Bolhar (1), Uwe Ring (2), Charlotte M. Allen (3) Keywords: Aegean Sea; Cyclades; Granitoids; Hellenic subduction zone; I-type; S-type; Zircon geochronology Abstract: We use 369 individual U--Pb zircon ages from 14 granitoid samples collected on five islands in the Cyclades in the Aegean Sea, Greece, for constraining the crystallisation history of I- and S-type plutons above the retreating Hellenic subduction zone. Miocene magmatism in the Cyclades extended over a time span from 17 to 11 Ma. The ages for S-type granites are systematically ~2 million years older than those for I-type granites. Considering plutons individually, the zircon data define age spectra ranging from simple and unimodal to complex and multimodal. Seven of the 14 investigated samples yield more than one distinct zircon crystallisation age, with one I-type granodiorite sample from Mykonos Island representing the most complex case with three resolvable age peaks. Two samples from S-type granites on Ikaria appear to have crystallised zircon over 2--3 million years, whereas for the majority of individual samples with multiple zircon age populations the calculated ages deviate by 1--1.5 million years. We interpret our age data to reflect a protracted history involving initial partial melting at deeper lithospheric levels, followed by crystallisation and cooling at shallower crustal levels. Our study corroborates published research arguing that pluton construction is due to incremental emplacement of multiple magma pulses over a few million years. Assuming that multiple age peaks of our 14 samples can indeed serve to quantify time spans for magmatic emplacement, our data suggest that Aegean plutons were constructed over a few million years. Our tectonic interpretation of the U--Pb ages is that the S-type granites resulted from partial melting and migmatisation of the lower crust, possibly starting at ~23 Ma. The I-type granites and associated mafic melts are interpreted to reflect the magmatic arc stage in the Cyclades starting at ~15 Ma. Author Affiliation: (1) School of Earth Sciences, University of Queensland, Brisbane, 4072, Australia (2) Department of Geological Sciences, University of Canterbury, Christchurch, 8140, New Zealand (3) Research School of Earth Sciences, Australian National University, Canberra, 2006, Australia Article History: Registration Date: 23/02/2010 Received Date: 16/03/2009 Accepted Date: 23/02/2010 Online Date: 27/03/2010 Article note: Communicated by C. Ballhaus. Electronic supplementary material The online version of this article (doi: 10.1007/s00410-010-0504-4) contains supplementary material, which is available to authorized users.

Byline: Marieke Lichtervelde (1), Francois Holtz (1), John M. Hanchar (2) Keywords: Manganotantalite; Zircon; Solubility; Dissolution and crystallization experiments; Competition; Pegmatite Abstract: The behavior of tantalum and zirconium in pegmatitic systems has been investigated through the determination of Ta and Zr solubilities at manganotantalite and zircon saturation from dissolution and crystallization experiments in hydrous, Li-, F-, P- and B-bearing pegmatitic melts. The pegmatitic melts are synthetic and enriched in flux elements: 0.7--1.3 wt% [Li.sub.2]O, 2--5.5 wt% F, 2.8--4 wt% [P.sub.2]O.sub.5 and 0--2.8 wt% [B.sub.2]O.sub.3, and their aluminum saturation index ranges from peralkaline to peraluminous (ASI.sub.Li = Al/[Na + K + Li] = 0.8 to 1.3) with various K/Na ratios. Dissolution and crystallization experiments were conducted at temperatures varying between 700 and 1,150degC, at 200 MPa and nearly water-saturated conditions. For dissolution experiments, pure synthetic, end member manganotantalite and zircon were used in order to avoid problems with slow solid-state kinetics, but additional experiments using natural manganotantalite and zircon of relatively pure composition (i.e., close to end member composition) displayed similar solubility results. Zircon and manganotantalite solubilities considerably increase from peraluminous to peralkaline compositions, and are more sensitive to changes in temperature or ASI of the melt than to flux content. A model relating the enthalpy of dissolution of manganotantalite to the ASI.sub.Li of the melt is proposed: aH .sub.diss (kJ/mol) = 304 x ASI.sub.Li - 176 in the peralkaline field, and aH .sub.diss (kJ/mol) = -111 x ASI.sub.Li + 245 in the peraluminous field. The solubility data reveal a small but detectable competitivity between Zr and Ta in the melt, i.e., lower amounts of Zr are incorporated in a Ta-bearing melt compared to a Ta-free melt under the same conditions. A similar behavior is observed for Hf and Ta. The competitivity between Zr (or Hf) and Ta increases from peraluminous to peralkaline compositions, and suggests that Ta is preferentially bonded to non-bridging oxygens (NBOs) with Al as first-neighbors, whereas Zr is preferentially bonded to NBOs formed by excess alkalies. As a consequence Zr/Ta ratios, when buffered by zircon and manganotantalite simultaneously, are higher in peralkaline melts than in peraluminous melts. Author Affiliation: (1) Institut fur Mineralogie, Leibniz Universitat Hannover, Callinstr. 3, 30167, Hannover, Germany (2) Department of Earth Sciences, Memorial University of Newfoundland, 300 Prince Philip Drive, St. John's, NL, A1B 3X5, Canada Article History: Registration Date: 26/10/2009 Received Date: 07/05/2009 Accepted Date: 26/10/2009 Online Date: 12/11/2009 Article note: Communicated by H. Keppler.

Byline: Jiang-Feng Qin (1), Shao-Cong Lai (1), Chun-Rong Diwu (1), Yin-Juan Ju (1), Yong-Fei Li (2) Keywords: Triassic adakitic granite; Mafic microgranular enclaves; Zircon Hf isotope; U--Pb dating; Magma mixing; Reworking of Neoproterozoic lithosphere Abstract: Petrogenesis of high Mg adakitic rocks in intracontinental settings is still a matter of debate. This paper reports major and trace element, whole-rock Sr--Nd isotope, zircon U--Pb and Hf isotope data for a suite of adakitic monzogranite and its mafic microgranular enclaves (MMEs) at Yangba in the northwestern margin of the South China Block. These geochemical data suggest that magma mixing between felsic adakitic magma derived from thickened lower continental crust and mafic magma derived from subcontinental lithospheric mantle (SCLM) may account for the origin of high Mg adakitic rocks in the intracontinental setting. The host monzogranite and MMEs from the Yangba pluton have zircon U--Pb ages of 207 +- 2 and 208 +- 2 Ma, respectively. The MMEs show igneous textures and contain abundant acicular apatite that suggests quenching process. Their trace element and evolved Sr--Nd isotopic compositions [[(.sup.87]Sr/ [.sup.86]Sr).sub.i = 0.707069--0.707138, and [epsilon].sub.Nd(t) = -6.5] indicate an origin from SCLM. Some zircon grains from the MMEs have positive [epsilon].sub.Hf(t) values of 2.3--8.2 with single-stage Hf model ages of 531--764 Ma. Thus, the MMEs would be derived from partial melts of the Neoproterozoic SCLM that formed during rift magmatism in response to breakup of supercontinent Rodinia, and experience subsequent fractional crystallization and magma mixing process. The host monzogranite exhibits typical geochemical characteristics of adakite, i.e., high La/Yb and Sr/Y ratios, low contents of Y (9.5--14.5 ppm) and Yb, no significant Eu anomalies (Eu/Eu* = 0.81--0.90), suggesting that garnet was stable in their source during partial melting. Its evolved Sr--Nd isotopic compositions [[(.sup.87]Sr/ [.sup.86]Sr).sub.i = 0.7041--0.7061, and [epsilon].sub.Nd(t) = -3.1 to -4.3] and high contents of [K.sub.2]O (3.22--3.84%) and Th (13.7--19.0 ppm) clearly indicate an origin from the continental crust. In addition, its high Mg (51--55), Cr and Ni contents may result from mixing with the SCLM-derived mafic magma. Most of the zircon grains from the adakitic monzogranite show negative [epsilon].sub.Hf(t) values of -9.4 to -0.1 with two-stage Hf model ages of 1,043--1,517 Ma some zircon grains display positive [epsilon].sub.Hf(t) of 0.1--3.9 with single-stage Hf ages of 704--856 Ma. These indicate that the source region of adakitic monzogranite contains the Neoproterozoic juvenile crust that has the positive [epsilon].sub.Hf(t) values in the Triassic. Thus, the high-Mg adakitic granites in the intracontinental setting would form by mixing between the crustal-derived adakitic magma and the SCLM-derived mafic magma. The mafic and adakitic magmas were generated coevally at Late Triassic, temporally consistent with the exhumation of deeply subducted continental crust in the northern margin of the South China Block. This bimodal magmatism postdates slab breakoff at mantle depths and therefore is suggested as a geodynamic response to lithospheric extension subsequent to the continental collision between the South China and North China Blocks. Author Affiliation: (1) State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, 710069, Xi'an, China (2) Shenyang Institute of Geology and Mineral Resources, 110032, Shenyang, China Article History: Registration Date: 29/07/2009 Received Date: 09/03/2009 Accepted Date: 29/07/2009 Online Date: 14/08/2009 Article note: Communicated by T.L. Grove.

The anode materials that have been developed for solid oxide fuel ceils (SOFCs) are vulnerable to deactivation by carbon buildup (coking) from hydrocarbon fuels or by sulfur contamination (poisoning). We report on a mixed ion conductor, Ba[Zr.sub.0.1][Ce.sub.0.7][Y.sub.0.2-x][Yb.sub.x][O.sub.3-[delta]] , that allows rapid transport of both protons and oxide ion vacancies. It exhibits high ionic conductivity at relatively Low temperatures (500[degrees] to 700[degrees]C). Its ability to resist deactivation by sulfur and coking appears linked to the mixed conductor's enhanced catalytic activity for sulfur oxidation and hydrocarbon cracking and reforming, as well as enhanced water adsorption capability.

The [epsilon]Hf and [[delta].sup.18]O values in detrital zircons from the Slave craton, Canada, indicate three episodes of crust formation between ca. 4.5 and 2.8 Ga, namely at ca. 4.4-4.5 Ga, ca. 3.8 Ga, and ca. 3.4 Ga. Most of the juvenile crust appears to have been mafic in composition, and there is no clear evidence for initial granitic protocrust in the Hadean of the Slave craton. The range of initial [epsilon]Hf values in zircons increases from 3.9 to 2.8 Ga, indicating that both extraction of new material from mantle and reworking of the older crust are important for the secular evolution of the continental crust. A preliminary review of available Hf data in zircons suggests that the three episodes of crust generation may have been of global importance. The mafic crust formed in the Archean and the Hadean was then reworked for at least ~0.5-1.5 b.y., as indicated by data from the Slave craton, Gondwana, and the Limpopo Belt of Africa.

Byline: Hakon Austrheim (1), Christine V. Putnis (2), Ane K. Engvik (3), Andrew Putnis (2) Keywords: Zircon; Ilmenite; Rutile; Titanite; Coronas; Metamorphic and metasomatic reactions Abstract: Ilmenite in coronitic gabbros from the Bamble and Kongsberg sectors, southern Norway, is surrounded by zircons ranging in diameters from a fraction of a micrometer to 10 um across. The zircons are inert during subsequent metamorphism (amphibolite- to pumpellyite--prehnite facies) and metasomatism (scapolitization and albitization) and can be found as trails in silicates (phlogopite, talc, chlorite, amphibole, albite, and tourmaline) in the altered rocks. The trails link up to form polygons outlining the former oxide grain boundary. This 3-dimensional framework of zircons is used to (a) recognize metasomatic origin of rocks, (b) quantify the mobility of elements during mineral replacement, (c) establish the growth direction of reaction fronts and to identify the reaction mechanism as dissolution--reprecipitation. Zircon coronas on Fe--Ti oxides have been described from a number of terrains and appear to be common in mafic rocks (gabbros and granulites) providing a tool for a better understanding of metasomatic and metamorphic reactions. Author Affiliation: (1) Physics of Geological Processes (PGP), University of Oslo, PO Box 1048, Blindern, 0316, Oslo, Norway (2) Institut fur Mineralogie, University of Munster, Correnstrasse 24, Munster, Germany (3) Geological Survey of Norway, Leiv Eirikssonsvei 39, 7491, Trondheim, Norway Article History: Registration Date: 17/03/2008 Received Date: 05/11/2007 Accepted Date: 17/03/2008 Online Date: 28/03/2008 Article note: Communicated by J. Hoefs.

An immense wedge of Carboniferous to Jurassic siliciclastic strata accumulated on the Verkhoyansk passive margin of the Siberian craton. U-Pb ages of detrital zircons from Pennsylvanian to Middle Jurassic sandstones are remarkably consistent and show a systematic change in the proportion of age populations. Most zircons originated from the southern margin of Siberia, which was tectonically active in the Paleozoic and early Mesozoic, and were transported to the Verkhoyansk margin by a major transcontinental river system that existed for ~200 m.y., the paleo-Lena River. Specific sources are the Angara-Vitim batholith of Transbaikalia (315 and 291-288 Ma age peaks), plutons of the Altay-Sayan region of the Central Asia fold belt (494-482 Ma), Proterozoic granitoids of northern Transbaikalia and the East Sayan Range (1888-1832 Ma), and minor contributions from the Siberian Platform and Aldan Shield (2900-2300 Ma). The paleo-Lena River met its demise when the Verkhoyansk margin was deformed in the Late Jurassic and Cretaceous, and sediment was diverted north to the Arctic Ocean. Thus, the life span of major transcontinental drainage systems can be comparable to that of the plate boundaries that surround them. Keywords: Siberia, Verkhoyansk, sedimentary provenance, detrital zircon.

The mechanism of reversible alkyne coupling at zirconium is examined by investigating the kinetics of zirconacyclopentadiene cleavage to produce free alkynes. The rates are shown to be largely affected by the steric properties of the ancillary ligands.

Several organic additives are employed for the synthesis of pore-size tunable mesoporous zirconium organophosphonates with chiral L-proline. These substrates can be easily used for enzyme adsorption, as the L-proline helps in the adsorption of papain at a lower pH value.

The potential energy surface of the reaction [[[([[eta].sup.5]-[C.sub.5][Me.sub.n][H.sub.5-n]).sub.2]M].sub.2]([[mu].sub.2], [[eta].sup.2], [[eta].sup.2]-[N.sub.2])+[H.sub.2]->[[[([[eta].sup.5]-[C.sub.5][Me.sub.n][H.sub.5-n]).sub.2]M].sub.2]([[mu].sub.2], [[eta].sup.2], [[eta].sup.2]-NNH) was investigated using density functional methods. The results indicate that [[[([[eta].sup.5]-[C.sub.5][Me.sub.n][H.sub.5-n]).sub.2]M].sub.2]([[mu].sub.2], [[eta].sup.2], [[eta].sup.2]-[N.sub.2]) complex cannot react with an [H.sub.2] molecule for M=Ti while those for M=Zr and Hf can.

An attempt is made to study the nonchelated alkene complexes of the [d.sup.0]-metal species, to probe the [Zr.sup.IV]-alkene interaction. Alkene coordination is inhibited by sterically bulky substituents on the alkene but is greatly enhanced by electron-donating groups and the [beta]-Si effect.

A series of diarylamido-phosphine complexes of zirconium and hafnium are presented and their structural characterization are established by means of solution NMR spectroscopy and X-ray crystallography. These compounds represent the rarely encountered triarylphosphine complexes of group 4 metals.

Addition of terminal alkynes has accomplished the functionalization of the N(sub 2) ligand in the side-on bound dinitrogen complex,[(eta(super 5)-C(sub 5)Me(sub 4)H)(sub 2)Zr](sub 2)(mu(sub 2), eta(sub 2), eta(sub 2)-N(sub 2) to furnish acetylide zirconocene diazenido complexes. These studies highlight the importance of cyclopentadienyl substituents on transformations involving coordinated dinitrogen.

The reaction of [(triple bondSiO)Zr(CH2tBu)(sub 3)] with H2 at 150 degreeC leads to the hydrogenolysis of the zirconium-carbon bonds to form a very reactive hydride intermediates. Their structural identities were identified by solid-state NMR techniques.

The Raman and infrared (IR) study of various layered zirconium and titanium acid phosphates of alpha- and gamma-type, alpha-M[O3POH](sub 2).H2O and gamma-M[PO4][O2P(OH)(sub 2)].2H2O, is described. A simple theoretical model, based on the interaction between the [PO4] unit and four Li(super +) in similar geometrical arrangement found in the structures of the layered phosphates, explains about the high-energy shift observed in the layered phosphates.

Charge trapping in high-permittivity metal oxides grown on Si using various types of chemical vapor deposition (CVD) was studied using generation of electron-hole pairs. For most CVD methods, thin oxides films exhibit positive charging; negative charge is observed only in as-deposited nitrogen -containing films.

First-principle plane-wave pseudopotential calculations have been conducted to investigate the atomic structure and energies of Sm123/BZO and Sm123/MgO interfaces, in this article. The results suggest that the insertion of a BZO buffer layer facilitates the epitaxial growth of Sm123 films on MgO substrates because of the energetically favorable film/buffer layer interface.

The rates of dehydrogenation of the sodium alanates NaAIH4 and Na3AIH6 doped with 2 mol percent titanium (Ti) or zirconium (Zr) are measured over the temperature range 363-423 K. NaAIH4 and Na3AIH6 undergo dehydrogenation at equal rates upon direct doping with titanium.

Highly electrophilic, 'cation like' organozirconium species are formed on sulfated alumina (AIS) and that such species exhibit high olefin polymerization activity, as well as appreciable benzene hydrogenation activity. A chemisorptive property of several classes of organozirconium hydrocarbyls on sulfated gamma-alumina is reported.

Catalytic asymmetric aldol reactions of silyl enol ethers with aldehydes are performed using novel chiral zirconium catalysts. The activities of the chiral zirconium catalysts are enhanced by using new ligands, (R)-3,3'-l2-6,6'-X2BINOL (X = Br, I, C2F5), and it is shown that even aldol reactions of less reactive substrates proceeded smoothly using the novel zirconium catalysts. The alcohol played an important role in the catalysts turnover, and water affected the formation of the catalyst.

The insertion reaction of transition metal cation doublet Zr+(2D) into HF, HCL, H2O, H2S, NH3, PH3, CH4, and SiH4 are investigated by means of ab initio molecular orbital calculations incorporating electron correlation with the Moller-Plesset perturbation theory up to the second and the fourth orders and the hybrid density functional method, B3LYP. The observed trends are to be understood by a combined effect of the electrostatic interaction and the covalent interaction.

The stationary points on both triplet and singlet potential energy surfaces for the gas-phase reaction system of Zr + C2H4 are reported by using the B3LYP density functional theory (DFT) with a large basis set. All intermediates and transition structures of the reaction system along with reaction mechanism are described for singlet and triplet pathway in order to probe product kinetic energy distributions.

Ultrasound radiation was used to prepare Eu2O3 dd in zirconia and yttrium-stabilized zirconium (YSZ) nanoparticles. Time decay measurements of the doped and coated materials were conducted using a pulsed laser source and accordingly longer lifetimes were measured when the doped and coated samples were annealed at 700 degrees Celsius and shorter lifetimes were attributed to concentration quenching.

The calculations of total and binding energies of group IV tetrachlorides MCl4(M = Ti, Zr, Hf, and element 104, Rf) are performed using the four-component fully relativistic density functional method. The calculations show the binding energies to be in good agreement with thermochemical dissociation energies obtained via the Born-Haber. The method demonstrates a predictive power, which is important for further applications in the area of the heavy element compounds.

New examples of the novel reactivity possessed by zirconium and hafnium imido metalloporphyrin complexes are demonstrated and direct synthetic routes are developed to zirconium metalloporphyrin complexes containing bridging oxygen ligands. These complexes mediate the stepwise coupling of pinacolone in the formation of an enediolate compound.

Geochemical data and U-Pb zircon results are presented for the intrusive meta-igneous rocks of the Ongole domain, a granulite-facies terrain of the Eastern Ghats Belt in India, with the aim of inferring the tectonic setting and the timing of their formation. Geochemical data suggest that the intrusive meta-igneous rocks (mafic granulites and charnoenderbites) possess trace and rare earth element composition that are typical of magmatic arcs. They are subalkaline, enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high field strength elements like Nb, Ta and Ti. These characteristics indicate that the primary magmas of these rocks were derived by partial melting of a depleted mantle wedge that had been metasomatized by a slab component. Zircon grains collected from five charnoenderbites are large and euhedral to subhedral and display fine-scale oscillatory growth zoning in CL images, implying a magmatic origin. The grains frequently show narrow-to-broad unzoned overgrowths, implying a metamorphic origin. The oscillatory-zoned cores yield Paleoproterozoic concordia ages of ca. 1,750-1,710 Ma, interpreted as the time of magma emplacement. The unzoned overgrowths yield very late Paleoproterozoic ages of ca. 1,630-1,600 Ma, interpreted as the timing of metamorphism. An enderbite showing both magmatic and metamorphic concordia ages of ca. 1,605 Ma points to the existence of syn-metamorphic intrusions. Together, the presented geochemical and geochronological evidence suggests that the Ongole domain was a magmatic arc near the Indian continent during the Paleoproterozoic. Subsequently, the rocks were metamorphosed during the late Paleoproterozoic, and the terrain was accreted to the Indian craton during the early Mesoproterozoic. The formation and growth of the Ongole domain magmatic arc through subduction-related accretion can be correlated with the growth of Columbia (1.8-1.2 Ga), but its accretion to the Indian craton is apparently unrelated to the formation of any super-continent on a global scale. Keywords Eastern Ghats Belt * Ongole domain * Geochemistry * LA-ICP-MS zircon geochronology * Columbia supercontinent, Introduction The formation and subsequent evolution of continental crust from the Archean to the present is one of the key topics in earth sciences that is widely debated (Condie 2000; [...]

A new synthetic strategy for the preparation of a terminal monohydoxide of gallium containing a methyl group on gallium is described. The resulting compound LGa(Me)OH can be used as a synthon to prepare novel hetero-bimetallic derivatives and it reacts with Cp(sub 2)ZrMe(sub 2) to yield [(LGaMe))Cp(sub 2-)ZrMe)](mu-O).

The unprecedented acceleration of zirconium (IV)-assisted peptide hydrolysis at neutral pH is detailed. An overall preference for cleavage of neutral and negatively charged particles containing glycine and amino acids with oxygen rich side chains is observed.

The Warburton Basin of central Australia has experienced a complex tectonic and fluid-flow history, resulting in the formation of various authigenic minerals. Geochemical and geochronological analyses were undertaken on vein carbonates from core samples of clastic sediments. Results were then integrated with zircon U-Pb dating and uraninite U-Th-total Pb dating from the underlying granite. Stable and radiogenic isotopes (δ[sup.18]O, Sr and ζNd), as well as trace element data of carbonate veins indicate that >200 °C basinal fluids of evolved meteoric origin circulated through the Warburton Basin. Almost coincidental ages of these carbonates (Sm-Nd; 432 ± 12 Ma) with primary zircon (421 ± 3.8 Ma) and uraninite (407 ± 16 Ma) ages from the granitic intrusion point towards a substantial period of active tectonism and an elevated thermal regime during the mid Silurian. We hypothesise that such a thermal regime may have resulted from extensional tectonism and concomitant magmatic activity following regional orogenesis. This study shows that the combined application of geochemical and geochronological analyses of both primary and secondary species may constrain the timing of tectonomagmatic events and associated fluid flow in intraplate sedimentary basins. Furthermore, this work suggests that the Sm-Nd-isotopic system is surprisingly robust and can record geologically meaningful age data from hydrothermal mineral species. Keywords Thermal and tectonic history * Warburton Basin * [sup.147]Sm-[sup.144]Nd geochronology * Water-rock interaction * Vein carbonates, Introduction Thermal perturbations experienced by sedimentary basins can result from a number of processes including emplacement of magmatic bodies and lithospheric thinning due to extensional tectonism (Armstrong 2005). Tensional stress [...]

The neutron diffraction analysis on Zr and Ti substituted 2:14:1 compounds is discussed. The lattice expands in the Ti-containing melt spun alloy of (NdPr)FeB and Ti is present on the j1, j2 sites that are normally occupied by Fe.

Several solid-state [91 sup]Zr NMR spectroscopy studies are conducted to explain the formation, structure and properties of the zirconocene olefin polymerization catalyst precursors. The approach is shown to be extremely beneficial for studying the molecular structure of various such catalysts.

A study was conducted to understand the strong negative thermal expansion (NTE) exhibited by scandium trifluoride at low temperature, which maintains a cubic Re[O.sub.3] type structure down to at least 10K. Sc[F.sub.3] is found to be the first material with structure similar to Re[O.sub.3] which provide a clear experimental explanation for the observed NTE mechanism.

Kinetic, stoichiometric and structural studies are used for examining the mechanism of hydroamination/cyclization of primary aminoalkenes by catalysts based on Cp*LZr[(N[Me.sub.2]).sub.2] (L u [k.sup.2]-salicycloxazoline). Thermodynamic parameters extracted from independent kinetic studies have shown moderate ordering and substantial overall bond disruption in the rate-determining transition state.

A novel method is developed for determining the fraction of initiated catalyst by using standard gel-permeation chromatography (GPC). The polymer-bound label is quantified as a function of polymer molecular weight by using a GPC with a UV detector and simultaneous RI detection has allowed both the extent of monomer conversion and the molecular-weight distribution to be established.

The t-BuCN-stabilized zirconacyclopropene-azasilacyclopentadiene complexes 2 are generated in situ in high yields from the Si-tethered diynes ([Cp.sub.2]Zr(II) species) and 2 equiv of t-BuCN through the coordination-induced Zr-C/Si-C bond cleavage and reorganization. t-BuCN has behaved as both an initiator and a brake/release handle to initiate and control the reaction process.

The alkylaluminum-complexed zirconocene trihydride cation [[(SBI)Zr[([mu]-H).sub.3][(Al[super i][Bu.sub.2]).sub.2]].sup.+] has catalyzed the formation of isotactic polypropene when exposed to propene. The exposure to propene has caused the trihydride cation to be completely converted to the doubly Me-bridged cation [[(SBI)Zr[([mu]-Me).sub.2]Al[Me.sub.2]].sup.+] in the presence of Al[Me.sub.3].

The structure-property relationships of zirconia-supported tungsten oxide (W[O.sub.x]/Zr[O.sub.2]), considered as an important supported metal oxide model acid catalyst is explored for numerous acid-catalyzed reactions. Analysis of tungsten oxide for n-pentane isomerization activity and selectivity as a function of tungsten surface density, catalyst support type, and calcination temperature revealed (W[O.sub.x]/Zr[O.sub.2]) to exhibit isomerization activity that peaked within the first 2 h time-on-stream, which might be due to Zr-W[O.sub.x] clusters undergoing an activation process.

The remarkable migratory insertion reactions of 2,2-disubstituted-1-alkenes, intramolecular 1,5-[sigma] bond metathesis via [epsi]-agostic interactions, and a rare example of a [beta]-agostic alkyltitanocene are discussed. The observed titanocene-based chemistry contrasted starkly to that of the analogous zirconium system, in which the unusual but well-characterized cationic methyl alkene complex [[Cp.sub.2]ZrMe(DMP)](+) does not undergo migratory insertion and subsequent reactions.