Showing papers by "Alan Davison published in 1989"
TL;DR: The reaction of (TcCl{sub 4}(PPh{sub 3}{sub 2}(NNPh)(NNHPh) ) with arylhydrazines in methanol yields (tcClCl(pPh{ sub 3}(nph{sub 6} (NNPh))(1) ) (1) as mentioned in this paper.
Abstract: The reaction of (TcCl{sub 4}(PPh{sub 3}){sub 2}) with arylhydrazines in methanol yields (TcCl(PPh{sub 3}){sub 2}(NNPh){sub 2}) (1). Complex 1 displays trigonal-bipyramidal geometry with phosphine ligands occupying axial sites. The technetium-aryldiazenido moieties are nearly equivalent, with Tc-N-N bond angles of 166.2 (6) and 170.7 (7){degree} and multiple bonding throughout. The chloride ligand occupies the remaining equatorial coordination site. The addition of HCl(g) to complex 1 in methanol gives the neutral, six-coordinate hydrazido(2-) complex (TcCl{sub 2}(PPh{sub 3}){sub 2}(NNPh)(NNHPh)). The reaction of complex 1 with HBr(g) gives the doubly protonated, cationic species (TcBr{sub 2}(PPh{sub 3}){sub 2}(NNPh)(NHNHPh))(Br). The {sup 99}Tc NMR spectra for these species are presented, which suggest that the metals exhibit considerable Tc(V) character and that the formal oxidation states of {minus}1 and +1 are not accurate ddescriptions of the electron density on the technetium. The {sup 1}H NMR, mass, and electronic spectroscopic data are also presented for the various species, along with the crystal structure of the five-coordinate bis(aryldiazenido) precursor. Crystal data for C{sub 48}H{sub 38}N{sub 4}P{sub 2}ClBr{sub 2}Tc are presented.
53 citations
TL;DR: Results indicated that, following intravenous administration, complexes of low lipophilicity yielded suboptimal myocardial images because of low heart cell uptake, whereas complexes of high lipophILicity yielded poor relative myocardIAL visualization because of excessive binding to additional organs and compartments.
Abstract: Hexakis (alkylisonitrile) technetium(I) complexes are a new class of cationic, lipophilic myocardial perfusion imaging agents. To further evaluate the effect of lipophilicity on myocardial uptake characteristics, the authors systematically synthesized and tested Tc-isonitrile complexes of varying lipophilicity in both cellular and whole animal systems. In chick heart cells in monolayer culture, cellular plateau level uptake in general correlated with lipophilicity of the complexes (determined by reverse phase high performance liquid chromatography) (r = .71) as well as with scintigraphic intensity of imaged rabbit hearts (r = .91). Exceptions to this trend indicated that additional factors such as size of the complex and form of the terminal alkyl chain branching also may have influenced uptake. The data indicated that neither the lipophilic properties nor the cation charge alone were sufficient to predict myocardial uptake. In addition, intravenous injection of complexes into rabbits showed optimal myocardial images with agents of intermediate lipophilicity. Results indicated that, following intravenous administration, complexes of low lipophilicity yielded suboptimal myocardial images because of low heart cell uptake, whereas complexes of high lipophilicity yielded poor relative myocardial visualization because of excessive binding to additional organs and compartments.
50 citations
TL;DR: In this article, the preparation and characterization of trichloronitrosylbis(triphenylphosphine)technetium(III) from acetonitrile solvent is described.
Abstract: The preparation and characterization of (acetonitrile)trichlorobis(triphenylphosphine)technetium(III) from (n-Bu{sub 4}N)(TcOCl{sub 4}) with triphenylphospine in acetonitrile solvent is described. The potentially rich reaction chemistry of this complex is discussed in relation to ReCl{sub 3}(PPh){sub 2}(MeCN). Reactions of TcCl{sub 3}(PPh{sub 3}){sub 2}(MeCN) with CO and NO are described. Characterization of the products, carbonyltrichlorobis(triphenylphosphine)technetium(III) and trichloronitrosylbis(triphenylphosphine)technetium(II), is also described. The carbonyl complex, C{sub 37}H{sub 30}Cl{sub 3}OP{sub 2}Tc, which crystallizes in space group C2/c with a = 24.649 (9) {angstrom}, b = 9.530 (3) {angstrom}, c = 15.870 {angstrom}, {beta} = 116.40 (3){degree}, V = 3339 (4) {angstrom}{sup 3}, and Z = 4, was structurally characterized. The Tc-C bond distance of 1.985 (9) {angstrom} as well as the C{equivalent to}O stretching frequency of 2054 cm{sup {minus}1} is indicative of the absence of significant {pi}-back-bonding in this complex. 21 refs., 1 fig., 3 tabs.
45 citations
TL;DR: In this article, the chemical shifts and linewidths of a variety of technetium compounds in oxidation states V, III and I were measured, and the relationship between the shift and oxidation state, ligand field strength and shielding effects for these, and other previously measured compounds, were discussed.
40 citations
TL;DR: 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-triazayclonononane-N,N{prime},N{double prime}-triacetate) has been prepared as its sodium and barium salts as discussed by the authors.
Abstract: 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
34 citations
TL;DR: In this article, the initial product of the reaction of compound 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.
Abstract: 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
33 citations
25 citations
TL;DR: In this article, a hexahydrate was characterized by single-crystal x-ray crystallography, showing a centrosymmetric dianion with two square-pyramidal OTcS{sub 4}cores bridged 4-fold by the (H{sub 2}ema{sup 2{minus}}) dithiolate ligands.
Abstract: Reaction of (Bu{sub 4}N)(TcOCl{sub 4}) with a 5-fold excess of N,N{prime}-ethylenebis(2-mercaptoacetamide) (H{sub 4}ema) in methanolic sodium methoxide yielded a blue precipitate which was metathesized to give (AsPh{sub 4}){sub 2}(Tc{sub 2}O{sub 2}(H{sub 2}ema){sub 4}) (1). Complex 1 crystallized as a hexahydrate and was structurally characterized by single-crystal x-ray crystallography. The structure of the dianion showed a centrosymmetric dianion with two square-pyramidal OTcS{sub 4}cores bridged 4-fold by the (H{sub 2}ema{sup 2{minus}}) dithiolate ligands. The metal-oxo groups are oriented into the center of the cage created by the bridging ligands, giving what is referred to as a lantern structure. The intramolecular Tc-Tc* distance was 7.175 (4) {angstrom}, and the distance between the two metal oxo ligands, O1-O1*, was 3.96(2) {angstrom}. The six water molecules per dimer were found to be hydrogen-bonded to each other and to the amide NH and CO groups on the ligands. Compound 1 was converted to (AsPh{sub 4})(TcO(ema)) when heated in solution or when reacted with aqueous base. 19 refs., 3 figs., 5 tabs.
11 citations
Journal Article•
4 citations
Journal Article•
TL;DR: In this article, the reaction of (Bu 4 N)[TcOCl 4 ] with a 5-fold excess of N,N'-ethylenebis(2-mercaptoacetamide) (H 4 ema) in methanolic sodium methoxide yielded a blue precipitate which was metathesized to give (AsPh 4 ) 2 [Tc 2 O 2 (H 2 ema] 4 ].
Abstract: Reaction of (Bu 4 N)[TcOCl 4 ] with a 5-fold excess of N,N'-ethylenebis(2-mercaptoacetamide) (H 4 ema) in methanolic sodium methoxide yielded a blue precipitate which was metathesized to give (AsPh 4 ) 2 [Tc 2 O 2 (H 2 ema) 4 ]. Complex crystallized as a hexahydrate and was structurally characterized by single-crystal X-ray crystallography
2 citations
Patent•
15 May 1989
TL;DR: In analogy to its rhenium congener, the title complex (IV) promises to be a useful starting material for low-valent technetium chemistry as discussed by the authors, and it has been shown to be useful in many applications.
Abstract: In analogy to its rhenium congener, the title complex (IV) promises to be a useful starting material for low-valent technetium chemistry.