(η5‐Cyclopentadienyl)Tricarbonylmanganese(I) Complexes

Since the initial preparation of (η5‐C5H5)Mn(CO)3 by Fischer and Jira in 1954, many methods have been developed for the synthesis of this compound (often referred to as “cymantrene”) and its C5 substituted derivatives. Interestingly, each of these preparations has at least one significant drawback from a preparative perspective (thallium reagents, high pressures, poor yields, or reactants that require significant preparative investment). Surprisingly missing from this collection of preparative methods is the direct reaction between commercially available Mn(CO)5Br and NaC5H5. In 1988, however, Smart and coworkers found MnBr(CO)3(pyridine)2 to be an effective reagent in making a substituted indacenylmanganese tricarbonyl complex. As this pyridine complex also serves as an effective manganese starting material, this chapter discusses the high‐yield syntheses of cymantrene and its derivatives such as (η5‐C5Me5)Mn(CO)3

Theory for Phase Transitions in Insulating Vanadium Oxide

We show that the recently proposed S=2 bond model with orbital degrees of freedom for insulating V$_{2}$O$_{3}$ not only explains the anomalous magnetic ordering, but also other mysteries of the magnetic phase transition. The model contains an additional orbital degree of freedom that exhibits a zero temperature quantum phase transtion in the Ising universality class.Comment: 5 pages, 2 figure

Pre-pubertal Presentation of Peritoneal Inclusion Cyst Associated with Congenital Lower Extremity Venous Valve Agenesis

Low intraabdominal pressures are recommended for laparoscopic procedures in patients with lower extremity venous valve agenesis

Bundles over Nearly-Kahler Homogeneous Spaces in Heterotic String Theory

We construct heterotic vacua based on six-dimensional nearly-Kahler homogeneous manifolds and non-trivial vector bundles thereon. Our examples are based on three specific group coset spaces. It is shown how to construct line bundles over these spaces, compute their properties and build up vector bundles consistent with supersymmetry and anomaly cancelation. It turns out that the most interesting coset is $SU(3)/U(1)^2$. This space supports a large number of vector bundles which lead to consistent heterotic vacua, some of them with three chiral families.Comment: 32 pages, reference adde

Synthesis and X-ray Crystal Structure of [(C5Ph5)CrCl(μ-Cl)2Tl]2: An Example of the Rare M-X-TlI Linkage (X = Halide)

Reaction of solid TlCl with [(C5Ph5)CrCl(m-Cl)]2 in CH2Cl2 solvent yields the monomeric complex (C5Ph5)CrCl(m-Cl)2Tl in 80% isolated yield. The C5H5 and C5Me5 analogues do not react with TlCl suggesting a steric basis for the reaction of the C5Ph5 material. An X-ray crystal structure of [(C5Ph5)CrCl(m-Cl)2Tl]2•2CH2Cl2 was obtained

Fock space localization, return probability, and conductance of disordered interacting electrons

We numerically simulate the low-energy properties of interacting electrons in a random potential using the Hartree-Fock based exact diagonalization method. In particular, we investigate how the transport properties are influenced by the combined effects of disorder and correlations in the presence of the electron spin. To this end we calculate the participation number of many-particle states in Fock space, the return probability of single-particle excitations, and the Kubo-Greenwood conductance. It turns out that in the strongly localized regime interactions increase the conductance whereas for weak disorder interactions decrease the conductance. In contrast, single-particle excitations in general experience a localizing influence of the interactions.Comment: 4 pages, 4 eps figures, Proc. of the Symposium on Wave Propagation and Electronic Structure in Disordered Systems, FORTH, Heraklion, Crete, Greece (June 2000

Ground State and Excitations of Spin Chain with Orbital Degeneracy

The one dimensional Heisenberg model in the presence of orbital degeneracy is studied at the SU(4) symmetric viewpoint by means of Bethe ansatz. Following Sutherland's previous work on an equivalent model, we discuss the ground state and the low-lying excitations more extensively in connection to the spin systems with orbital degeneracy. We show explicitly that the ground state is a SU(4) singlet. We study the degeneracies of the elementary excitations and the spectra of the generalized magnons consisting of these excitations. We also discuss the complex 2-strings in the context of the Bethe ansatz solutions.Comment: Revtex, 9 pages, 3 figures; typos correcte

Substitution Reactions of (C5Ph5)Cr(CO)3: Structural, Electrochemical, and Spectroscopic Characterization of (C5Ph5)Cr(CO)2L, L = PMe3, PMe2Ph, P(OMe)3

The radical complex (C5Ph5)Cr(CO)3 reacts with small, neutral, monodentate Lewis bases (PMe3, PMe2Ph, P(OMe)3) in THF at −78 °C (PMe2Ph reacts at ambient temperature) to yield the monomeric substitution products (C5Ph5)Cr(CO)2L·THF as thermally stable solids. Electrochemical and spectroscopic data are provided. An X-ray crystal structure of the hemisolvate (C5Ph5)Cr(CO)2PMe3·0.5THF was obtained. Frozen-solution ESR spectra of (C5Ph5)Cr(CO)2L in toluene are comparable to those of other low-spin d5 “piano-stool” complexes. Rotation of the Cr(CO)2L moiety relative to the C5Ph5 ring is rapid on the ESR time scale in low-temperature liquid solutions and leads to axial powderlike spectra. Analysis of this effect leads to significant insights into the electronic structure

RR Lyrae Stars in the Bootes dSph

We present a catalog of 15 RR Lyrae variable stars in the recently discovered Bootes galaxy -- the most metal-poor simple stellar population with measured RR Lyrae stars. The pulsational properties of the RR Lyrae conform closely to period-abundance trends extrapolated from more metal-rich populations and we estimate the distance of Bootes to be (m-M)_0=18.96+-0.12. The average period (0.69 days), the ratio of type c to type ab pulsators (0.53) and the RRab period shift (-0.07) indicate an Oosterhoff II classification for Bootes, a marked contrast to the other dSph galaxies, which are Oosterhoff intermediate. This supports the contention that the Oosterhoff dichotomy is a continuum -- that RR Lyrae properties, to first order, vary smoothly with abundance. The dSph galaxies are not distinct from the Galactic globular clusters, but bridge the Oosterhoff gap. The absence of any anomalous Cepheids in Bootes could indicate the lack of an intermediate age population.Comment: 16 pages, submitted to Astrophysical Journal Letter