PCP Pincer Complexes of Titanium in the +3 and +4 Oxidation States.

Ti(IV) and Ti(III) complexes using the PCP ligand have been synthesized (PCP = CH-2,6-(CHPBu)). The [PCP]Li synthon can be reacted with TiCl(THF) to form (PCP)TiCl () in limited yields due to significant reduction of the titanium synthon. The Ti(III) complex (PCP)TiCl () has been further characterized.

Synthesis and reactivity of titanium 'POCOP' pincer complexes.

The 'POCOP' pincer ligand, [2,6-(OPR)CH], has been attached to titanium in both Ti(III) and Ti(IV) complexes for the first time. Using a lithium-halogen exchange route [2,6-(OPR)CH]Li ([RPOCOP]Li) can be synthesised. Both the -propyl and -butyl derivatives can be made, but only the latter isolated.

Hormone replacement therapy subcutaneous implants for refractory menopause symptoms; the patient's perspective.

Objective: For women with menopause symptoms refractory to standard hormone replacement therapy (HRT) preparations, HRT implants offer an alternative. The primary objective of this study was to evaluate women's perceptions regarding efficacy, tolerability, satisfaction and safety of implant therapy.

Study Design: A single centre service evaluation study performed at Birmingham Women's & Children's Foundation Hospital Trust.

Asymmetric bis-PNP pincer complexes of zirconium and hafnium - a measure of hemilability.

Asymmetrically-bound pyrrolide-based bis-PNP pincer complexes of zirconium and hafnium have been formed. The [κ2-PNPPh][κ3-PNPPh]MCl2 species are in direct contrast to previous zirconium PNP pincer complexes. The pincer ligands are fluxional in their binding and the energy barrier for exchange has been approximated using VT-NMR spectroscopy and the result validated by DFT calculations.

Brønsted and Lewis acid adducts of triazenes.

The synthetic utility of triazenes rests on the fact that the triazene function can be cleaved by Brønsted or Lewis acids, liberating diazonium compounds. However, the preferred coordination site of the acid is still a matter of debate. We have analyzed triflic acid, B(CF), and PdCl adducts of triazenes by NMR spectroscopy and single crystal X-ray crystallography.

Divergent Synthesis of Densely Substituted Arenes and Pyridines via Cyclotrimerization Reactions of Alkynyl Triazenes.

Densely substituted fused aromatic triazenes can be prepared by [2 + 2 + 2] cyclotrimerization reactions of 1-alkynyl triazenes. The Cp*Ru-catalyzed cyclization proceeds well with both simple alkynyl triazenes and tethered 1-diynyl triazenes. Attractively, the methodology can be extended to pyridine synthesis by replacing an alkyne with a nitrile.

Azo-MICs: Redox-Active Mesoionic Carbene Ligands Derived from Azoimidazolium Dyes.

Azoimidazolium dyes were used as precursors for mesoionic carbene ligands (Azo-MICs). The properties of these ligands were examined by synthesizing Rh , Au , and Pd complexes. Experimental (NMR, IR) and theoretical investigations show that Azo-MICs are potent σ-donor ligands.

Solid-state molecular organometallic chemistry. Single-crystal to single-crystal reactivity and catalysis with light hydrocarbon substrates.

Single-crystal to single-crystal solid/gas reactivity and catalysis starting from the precursor sigma-alkane complex (NBA = norbornane; Ar = 3,5-(CF)CH) is reported. By adding ethene, propene and 1-butene to this precursor in solid/gas reactions the resulting alkene complexes are formed. The ethene ( = 2) complex, , has been characterized in the solid-state (single-crystal X-ray diffraction) and by solution and solid-state NMR spectroscopy.

Selective C-H Activation at a Molecular Rhodium Sigma-Alkane Complex by Solid/Gas Single-Crystal to Single-Crystal H/D Exchange.

The controlled catalytic functionalization of alkanes via the activation of C-H bonds is a significant challenge. Although C-H activation by transition metal catalysts is often suggested to operate via intermediate σ-alkane complexes, such transient species are difficult to observe due to their instability in solution. This instability may be controlled by use of solid/gas synthetic techniques that enable the isolation of single-crystals of well-defined σ-alkane complexes.

Encapsulation of an organometallic cationic catalyst by direct exchange into an anionic MOF.

Metal-Organic Frameworks (MOFs) are porous crystalline materials that have emerged as promising hosts for the heterogenization of homogeneous organometallic catalysts, forming hybrid materials which combine the benefits of both classes of catalysts. Herein, we report the encapsulation of the organometallic cationic Lewis acidic catalyst [CpFe(CO)(L)] ([Fp-L], Cp = η-CH, L = weakly bound solvent) inside the pores of the anionic [EtN][In(BTC)] MOF (HBTC = benzenetricarboxylic acid) a direct one-step cation exchange process. To conclusively validate this methodology, initially [CpCo] was used as an inert spatial probe to (i) test the stability of the selected host; (ii) monitor the stoichiometry of the cation exchange process and (iii) assess pore dimensions, spatial location of the cationic species and guest-accessible space by single crystal X-ray crystallography.

A Rhodium-Pentane Sigma-Alkane Complex: Characterization in the Solid State by Experimental and Computational Techniques.

The pentane σ-complex [Rh{Cy2 P(CH2 CH2 )PCy2 }(η(2) :η(2) -C5 H12 )][BAr(F) 4 ] is synthesized by a solid/gas single-crystal to single-crystal transformation by addition of H2 to a precursor 1,3-pentadiene complex. Characterization by low temperature single-crystal X-ray diffraction (150 K) and SSNMR spectroscopy (158 K) reveals coordination through two Rh⋅⋅⋅H-C interactions in the 2,4-positions of the linear alkane. Periodic DFT calculations and molecular dynamics on the structure in the solid state provide insight into the experimentally observed Rh⋅⋅⋅H-C interaction, the extended environment in the crystal lattice and a temperature-dependent pentane rearrangement implicated by the SSNMR data.

Group 9 bimetallic carbonyl permethylpentalene complexes.

We describe the synthesis, structure and bonding of the first iridium and rhodium permethylpentalene complexes, syn-[M(CO)2]2(μ:η(5):η(5)-Pn*) (M = Rh, Ir). In fact, [Ir(CO)2]2(μ:η(5):η(5)-Pn*) is the first iridium pentalene complex. An interesting preference for the isolation of the sterically more demanding syn-isomer is observed and substantiated by DFT analysis.

Double CO2 activation by 14-electron η(8)-permethylpentalene titanium dialkyl complexes.

The novel 14 electron species η(8)-Pn*TiR2 (Pn* = C8Me6; R = Me, CH2Ph) have been synthesised and spectroscopically and structurally characterised. Subsequent reaction with CO2 leads to the activation and double insertion of CO2 into both Ti-alkyl bonds to form the electronically saturated η(8)-Pn*Ti(κ(2)-O2CR)2 (R = Me, CH2Ph) complexes.

A CH2Cl2 complex of a [Rh(pincer)](+) cation.

The CH2Cl2 complex [Rh((tBu)PONOP)(κ(1)-ClCH2Cl)][BAr(F)4] is reported, that also acts as a useful synthon for other complexes such as N2, CO and H2 adducts; while the analogous PNP complex undergoes C-Cl activation.

Solid-state synthesis and characterization of σ-alkane complexes, [Rh(L2)(η(2),η(2)-C7H12)][BAr(F)4] (L2 = bidentate chelating phosphine).

The use of solid/gas and single-crystal to single-crystal synthetic routes is reported for the synthesis and characterization of a number of σ-alkane complexes: [Rh(R2P(CH2)nPR2)(η(2),η(2)-C7H12)][BAr(F)4]; R = Cy, n = 2; R = (i)Pr, n = 2,3; Ar = 3,5-C6H3(CF3)2. These norbornane adducts are formed by simple hydrogenation of the corresponding norbornadiene precursor in the solid state. For R = Cy (n = 2), the resulting complex is remarkably stable (months at 298 K), allowing for full characterization using single-crystal X-ray diffraction.

Heterolytic activation of hydrogen using frustrated Lewis pairs containing tris(2,2',2''-perfluorobiphenyl)borane.

The extremely sterically hindered borane tris(2,2',2''-perfluorobiphenyl)borane (PBB) has been structurally characterised. In combination with bulky nitrogen bases, it forms the 'frustrated Lewis pairs' (FLPs) PBB/2,2,6,6-tetramethylpiperidine (TMP) (1), PBB/1,4-diazobicyclo[2.2.

ENDF nuclear data in the physical, biological, and medical sciences.

Purpose: This paper gives an overview of recent advances in the ENDF (Evaluated Nuclear Data File) database of neutron, proton, and photonuclear cross sections. ENDF nuclear data aim to provide accurate and comprehensive representations of all reaction processes that need to be simulated in radiation transport applications. The paper reviews some of the most importance capabilities embodied in the ENDF/B-VII.

Bis(permethylpentalene)uranium.

The reaction of Li(2)(C(14)H(18))(TMEDA)(x) with UCl(4) yields U(eta(8)-C(14)H(18))(2), (UPn*(2); Pn* = C(14)H(18)) an analogue of CePn*(2) and U{eta(8)-C(8)H(4)(1,4-Si(i)Pr(3))(2)}(2). The UPn*(2) molecule is structurally characterised via a variety of techniques, its magnetism is probed in the solution and solid phase and the redox properties are investigated using cyclic voltammetry. During this study it was shown to be reducible and the reduced species reacted with N(2)to form a stable complex.

Ion chamber gas-to-wall conversion factors for fast neutron dosimetry.

Modern ionising photon dosimetry is essentially entirely based upon gas-filled cavity determinations. For photons, ion chamber response is largely independent of photon energy almost perfectly transforming absorbed dose in the gas to the surrounding media. Absolute uncertainties are <1-2%.