Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

The use of conductivity measurements in organic solvents for the characterisation of coordination compounds

Organic chemists have always been fascinated by the cyclopropane subunit.1 The smallest cycloalkane is found as a basic structural element in a wide range of naturally occurring compounds.2 Moreover, many cyclopropane-containing unnatural products have been prepared to test the bonding features of this class of highly strained cycloalkanes3 and to study enzyme mechanism or inhibition.4 Cyclopropanes have also been used as versatile synthetic intermediates in the synthesis of more functionalized cycloalkanes5,6 and acyclic compounds.7 In recent years, most of the synthetic efforts have focused on the enantioselective synthesis of cyclopropanes.8 This has remained a challenge ever since it was found that the members of the pyrethroid class of compounds were effective insecticides.9 New and more efficient methods for the preparation of these entities in enantiomerically pure form are still evolving, and this review will focus mainly on the new methods that have appeared in the literature since 1989. It will elaborate on only three types of stereoselective cyclopropanation reactions from olefins: the halomethylmetal-mediated cyclopropanation reactions (eq 1), the transition metal-catalyzed decomposition of diazo compounds (eq 2), and the nucleophilic addition-ring closure sequence (eqs 3 and 4). These three processes will be examined in the context of diastereoand enantiocontrol. In the last section of the review, other methods commonly used to make chiral, nonracemic cyclopropanes will be briefly outlined.

Stereoselective Cyclopropanation Reactions

Publisher Summary This is one of two articles in this volume that is concerned with the borane-carborane structural pattern. In the other, Williams has shown how the pattern reflects the coordination number preferences of the various atoms involved. The purpose of the present article is to note some bonding implications of the pattern, and to show its relevance to a wide range of other compounds, including metal clusters, metal-hydrocarbon 7∼ complexes, and various neutral or charged hydrocarbons. Boranes and carboranes may be regarded as cluster compounds in the sense defined by Cotton; they contain a finite group or skeleton of atoms held together entirely, mainly, or at least to a significant extent by bonding directly between those atoms, even though some other atoms may be associated intimately with the cluster. Examples of their structural pattern, however, can be found far beyond the confines of what is normally regarded as cluster chemistry, so this survey includes many systems not commonly referred to as clusters.

Structural and Bonding Patterns in Cluster Chemistry

Porphyrin-based photosensitizers for use in photodynamic therapy

The mixed-valence technetium(III/IV) bis({mu}-oxo) dimer ((TCTA)Tc({mu}-O){sub 2}Tc(TCTA)){sup 3{minus}} (1; TCTA = 1,4,7-triazayclononane-N,N{prime},N{double prime}-triacetate) has been prepared as its sodium and barium salts. This complex undergoes a reversible on-electron oxidation with potassium persulfate to form ((TCTA)Tc({mu}-O){sub 2}Tc(TCTA)){sup 2{minus}} (2). Both complexes have been characterized by elemental analysis, infrared, UV/visible, and resonance Raman spectroscopy, and fast atom bombardment mass spectrometry. A crystal structure analysis of the Tc(III/IV) dimeter Ba{sub 2}((TCTA)Tc({mu}O){sub 2}Tc(TCTA))(ClO{sub 4}){center dot}9H{sub 2}O (1c) reveals that the two Tc atoms are linked by a planar Tc({mu}-O){sub 2}Tc ring. One TCTA ligand binds to each Tc through an N{sub 3}O donor set, and one of the acetate groups from each ligand bridges the two metal atoms. Resonance Raman spectra of complexes 1 and 2 were obtained by irradiation at 514.5 nm; strong bands assigned to the four-membered Tc({mu}-O){sub 2}Tc ring and the metal-metal multiple bond were seen. The aqueous electrochemistry of the compounds confirms that they are related by a reversible one-electron wave. The Tc(III/IV) dimer 1 represents the first fully characterized Tc-(amino carboxylate) complex in an oxidation state lower than +4. Evidence for the existence of other Tc(III/IV) bis({mu}-oxo) dimers of this type with amino carboxylate ligands such as EDTA andmore » NTA is presented. 23 refs., 3 figs., 4 tabs.« less

Technetium bis(.mu.-oxo) dimers of 1,4,7-triazacyclonane-N,N',N''-triacetate (TCTA). Synthesis and characterization of [(TCTA)Tc(.mu.-O)2Tc(TCTA)]n- (n = 2, 3) and the crystal structure of Ba2[(TCTA)Tc(.mu.-O)2Tc(TCTA)](ClO4).9H2O

Tris(o-mercaptophenyl) phosphinate (PS3) binds to Tc(III) as a tetradentate ligand to form the formally 14-electron complex Tc(PS3)(CNMe). An x-ray single-crystal structure determination of the isopropyl isocyanide derivative Tc(PS3)(CN-i-Pr) shows sulfurs bound in the equatorial plane. The crystal data for MF = C{sub 22}H{sub 19}NPS{sub 3}Tc is presented. In the presence of a large excess of isonitrile, these electron-deficient complexes bind a sixth ligand. The six-coordinate complex Tc(PS3)(CN-i-Pr){sub 2}, was also structurally characterized and the crystal data is presented. 8 refs., 2 figs., 4 tabs.

Technetium(III) complexes with the tetradentate "umbrella" ligand tris(o-mercaptophenyl)phosphinate: x-ray structural characterization of Tc(P(o-C6H4S)3)(CNC3H7) and Tc(P(o-C6H4S)3)(CNC3H7)2

Both Tc(III) compounds Tc(tmbt){sub 3}(MeCN){sub 2} (6) and Tc(tmbt){sub 3}(py){sub 2} (7) an be oxidized to Tc(V) oxo species by oxygen atom transfer. The initial product of the reaction of 6 with DMSO was characterized by x-ray crystallography and found to be Tc(tmbt){sub 3}(DMSO)(MeCN), the product of ligand substitution, not oxygen atom transfer. However, compound 6 is oxidized to TcO(tmbt){sub 3}(py) (1) by pyridine N-oxide, and 7 reacts with a number of other oxygen atom transfer reagents as well to produce the oxotechnetium(V) complex 1. The Tc(V) oxo compound TcO(SC{sub 15}H{sub 23}){sub 3}(NC{sub 5}H{sub 5}) (1) was also characterized by x-ray cyrstallography. Addition of excess thiolate to 1 yields (Ph{sub 4}As) (TcO(tmbt){sub 4}) (3), which can also be prepared directly from (Ph{sub 4}As)(TcOCl{sub 4}). Both 1 and 3 can be reduced by oxygen atom abstraction to restore the Tc(III) tris(thiolate) core. Reaction of 3 with PEt{sub 3} requires much more vigorous conditions than 1 does, but both materials are reduced to Tc(tmbt){sub 3}(PEt{sub 3}){sub 2}. The oxidative and reductive oxo-transfer reactions can be coupled to complete a catalytic cycle. In the oxidation of PPh{sub 3} by DMSO, the catalyst is still fully active after 500 turnovers. 31 refs., 5 figs.,more » 6 tabs.« less

Technetium thiolate complexes as oxygen atom transfer catalysts

Preparation et structure cristalline de complexes Tc(SC 10 H 13 ) 3 (CH 3 CN) 2 , Tc(SC 10 H 13 ) 3 (CO)(CH 3 CN) et Tc(SC 10 H 13 ) 3 (CO)(C 5 H 5 N)

Complexes of technetium(III) with sterically hindered arenethiolates and their interactions with small .pi.-accepting molecules

The synthesis and characterization of [MCl3(NNC5H4NH) (HNNC5H4N) from [MO4]− (where MRe, Tc) organodiazenido, organodiazene-chelate complexes. The X-ray structure of [ReCl3 (NNC5H4NH) (HNNC5H4N)]

Alan Davison

Papers

Technetium bis(.mu.-oxo) dimers of 1,4,7-triazacyclonane-N,N',N''-triacetate (TCTA). Synthesis and characterization of [(TCTA)Tc(.mu.-O)2Tc(TCTA)]n- (n = 2, 3) and the crystal structure of Ba2[(TCTA)Tc(.mu.-O)2Tc(TCTA)](ClO4).9H2O

Technetium(III) complexes with the tetradentate "umbrella" ligand tris(o-mercaptophenyl)phosphinate: x-ray structural characterization of Tc(P(o-C6H4S)3)(CNC3H7) and Tc(P(o-C6H4S)3)(CNC3H7)2

Technetium thiolate complexes as oxygen atom transfer catalysts

Complexes of technetium(III) with sterically hindered arenethiolates and their interactions with small .pi.-accepting molecules

The synthesis and characterization of [MCl3(NNC5H4NH) (HNNC5H4N) from [MO4]− (where MRe, Tc) organodiazenido, organodiazene-chelate complexes. The X-ray structure of [ReCl3 (NNC5H4NH) (HNNC5H4N)]