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71.
Reactor neutron activation analysis of antimony, indium and cadmium in high-purity tin is interfered with by nuclear reactions
on the tin matrix. For a number of interfering reactions the cross-sections were determined. The following results were obtained:122Sn(n,γ)123mSn:σth=0.145 barn, I=0.79 barn;122Sn(n,γ)113Sn:σth=0.52, I=25.4 barn;112Sn(n, 2n)111Sn:
microbarn;118Sn(n, α)115Cd:
microbarn; and114Sn(n, p)114m1In:
microbarn. 相似文献
72.
Qian-Feng Zhang Richard D. Adams Dieter Fenske 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3):275-279
The self-assemblies of two pyrogallol[4]arenes held together by 48 intermolecular hydrogen bonds stably associate in the form of spherical hexameric capsules. The molecular structures of two hexameric capsules with large interior space were analyzed by single crystal X-ray crystallography. 相似文献
73.
Christopher L. Hamblett David L. Sloman Bruce Adams Matthew G. Stanton 《Tetrahedron letters》2007,48(12):2079-2082
An efficient procedure for the preparation of trans-2,6-diaryl piperidinones has been developed. Addition of aryl Grignard reagents to 2-aryl dihydropyridones under catalytic copper promoted conditions generates the trans isomer exclusively, an unprecedented stereochemical event. The X-ray structures of both starting material and product have been solved and shed light on the steric constraints and substrate geometry leading to the observed product. The reaction conditions tolerate a variety of aromatic nucleophiles to generate C2-symmetric products in good overall yields. 相似文献
74.
Chris J. Adams Michael I. Bruce Brian W. Skelton Allan H. White 《Journal of Cluster Science》1994,5(3):419-441
The reactions between Ru5(
5-C2PPh2)(gm-PPh2(CO)13 (1) and cyclopentadienes afforded the hexanuclear clusters Ru6(
6-C)(
3-PPh2)2(CO)10(-C5
R
5) [R
5 = H5 (2), H4Me (3), Me5 (4)] which contain an encapsulated carbide and a face-capping
3-CH group, formed by cleavage of CC and CP bonds of the C2PPh2 moiety in1. In the reaction with cyclopentadiene, the unusual ligand C13H12O, formed by combination of C2, CO and two molecules of C5H6 (or one molecule of dicyclopentadien), was characterized in the complex Ru5(
4-PPh) (
4-C13H12O)(-PPh2(CO)11(-C5H5) (5). In the reaction with pentamethylcyclopentadiene, the vinylidene complex Ru5(
3-CCHPh)(
4-PPh)(
4-PPh) (-PPh2)(CO)9(-C5Me5) (6) was also formed. 相似文献
75.
A method was developed for the determination of 15 trace elements in tin. High-purity tin samples (99.9999% and 99.999%) as
well as tin of technical quality were analysed. Reactor neutron activation of the tin samples was followed by distillation
of the matrix activities from a HBr−H2SO4 medium and Ge(Li) gamma-ray spectrometry of the distillation residue. The sensitivity of the method is generally high. For
the high-purity samples the detection limits vary from 0.02 ppb (scandium) to 200 ppb (iron) for irradiation of 1 g of tin
for 1 week at a thermal flux of 5·1012n·cm−2. ·sec−1. To decontaminate the surface of the tin samples, pre- and post-irradiation etching procedures were applied. The efficiency
of these etching techniques was studied. 相似文献
76.
For a latticeL, aL is a fixed point ofL if and only iff(a)=a for every automorphismf ofL. Let Aut (L) andS (L) denote the group of automorphisms ofL and the sublattice of fixed points ofL, respectively. It is shown that ifG is a finite group other thanZ
2
2
,Z
2
3
,Z
2
4
,Z
3
2
or the quaternion group of order 8 andL is a finite automorphism free distributive lattice that is not near Boolean then there is a finite distributive latticeL such that Aut (L)G andS(L)L.The support of the National Research Council of Canada is gratefully acknowledged. 相似文献
77.
78.
Amarante D Cherian C Catapano A Adams R Wang MH Megehee EG 《Inorganic chemistry》2005,44(24):8804-8809
Five new mixed diimine 1,1'-dithiolate or dithiocarbamate ligand complexes of the form [Rh(bpy)2(SS)][PF6]n, where bpy = 2,2'-bipyridine and SS = various substituted dialkyldithiocarbamates or 1,1'-dithiolates, were synthesized from cis-[Rh(bpy)2(OTf)2][OTf]. The triflate ligands are easily displaced by other ligands and allow these syntheses to proceed in high yields (80-90% overall) under relatively mild reaction conditions and to give high purity products. Electrochemistry shows irreversible two-electron reduction of Rh(III) to Rh(I) and a concomitant loss of one bipyridine ligand; this is followed by reversible one-electron reduction of the remaining 2,2'-bipyridine ligand. The electronic characterizations of these complexes are consistent with significant delocalization of the sulfur electron density onto the empty metal d orbitals. The 1,1'-dithiolate ligands induce larger red shifts in the absorption and emission spectra than the dithiocarbamates as the 1,1'-dithiolates have a more extensive conjugation system. 相似文献
79.
Adams RD Captain B Herber RH Johansson M Nowik I Smith JL Smith MD 《Inorganic chemistry》2005,44(18):6346-6358
The reaction of Re2(CO)8[mu-eta2-C(H)=C(H)Bu(n)](mu-H) with Ph3SnH at 68 degrees C yielded the new compound Re2(CO)8(mu-SnPh2)2 (10) which contains two SnPh2 ligands bridging two Re(CO)(4) groups, joined by an unusually long Re-Re bond. Fenske-Hall molecular orbital calculations indicate that the bonding in the Re2Sn2 cluster is dominated by strong Re-Sn interactions and that the Re-Re interactions are weak. The 119Sn M?ssbauer spectrum of 10 exhibits a doublet with an isomer shift (IS) of 1.674(12) mm s(-1) and a quadrupole splitting (QS) of 2.080(12) mm s(-1) at 90 K,characteristic of Sn(IV) in a SnA2B2 environment. The IS is temperature dependent, -1.99(14) x 10(-4) mm s(-1) K(-1); the QS is temperature independent. The temperature-dependent properties are consistent with the known Gol'danskii-Kariagin effect. The germanium compound Re2(CO)8(mu-GePh2)2 (11) was obtained from the reaction of Re2(CO)8[mu-eta2-C(H)=C(H)Bu(n)](mu-H) with Ph3GeH. Compound 11 has a structure similar to that of 10. The reaction of 10 with Pd(PBu(t)3)2 at 25 degrees C yielded the bis-Pd(PBu(t)3) adduct, Re2(CO)8(mu-SnPh2)2[Pd(PBu(t)3)]2 (12); it has two Pd(PBu(t)3) groups bridging two of the four Re-Sn bonds in 10. Fenske-Hall molecular orbital calculations show that the Pd(PBu(t)3) groups form three-center two-electron bonds with the neighboring rhenium and tin atoms. The mono- and bis-Pt(PBu(t)3) adducts, Re2(CO)8(mu-SnPh2(2)[Pt(PBu(t)3)] (13) and Re2(CO)8(mu-SnPh2)2[Pt(PBu(t)3)]2 (14), were formed when 10 was treated with Pt(PBu(t)3)2. A mono adduct of 11, Re2(CO)8(mu-GePh2)2[Pt(PBu(t)3)] (15), was obtained similarly from the reaction of 11 with Pt(PBu(t)3)2. 相似文献
80.
López-Torres M Fernández A Fernández JJ Suárez A Pereira MT Ortigueira JM Vila JM Adams H 《Inorganic chemistry》2001,40(18):4583-4587
Reaction of cyclometalated halide-bridged Pd(II) complexes 1-4 with the tertiary triphosphine ligand (Ph2PCH2CH2)2PPh (triphos) yielded complexes [((Ph2PCH2CH2)2PPh-P,P,P)Pd(N(Cy)=(H)C)C6H2(C(H)=N(Cy))Pd((Ph2PCH2CH2)2PPh-P,P,P)][ClO4]2 5, [Pd(C6H4-N=NC6H5)((Ph2PCH2CH2)2PPh-P,P,P)][ClO4] 6, and [Pd(R-C6H3C(H)=NCy)((Ph2PCH2CH2)2PPh-P,P,P)][ClO4] (7; R = 4-CHO, 8; 3-CHO). Spectroscopic and analytic data suggest five-coordination on the palladium atom, which, for complexes 5, 6, and 7, was confirmed by X-ray crystallography. The geometry around palladium may be view as a distorted trigonal bipyramid, with the palladium, nitrogen, and terminal phosphorus atoms in the equatorial plane. Compound 5 is the first doubly cyclometalated palladium(II) compound with two pentacoordinated metal centers. The structure of 6 comprises two discrete cations with slightly different geometries, showing the importance of crystal packing forces in order to determine the coordination arrangement. 相似文献