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61.
Summary Organometallic compounds of general formula (SCN)2M(NCSeHgR)2 (M=CoII, NiII, R=n-C5H11,i-C5H11) have been prepared. They behave as Lewis acids, forming complexes with pyridine and 2,2-bipyridyl, characterized by elemental analysis, molecular weight, molar conductance, i.r. spectral (4000–200 cm–1), electronic spectral and magnetic susceptibility measurements. The Lewis acids are monomeric with bridging thiocyanate, or selenocyanate between M2+ and Hg2+. Cobalt and nickel acquire tetrahedral and octahedral configurations respectively through axial bridging, whereas mercury retains its linearity. Pyridine links to the metal in the Lewis acid and forms L2(SCN)2M(NCSeHgR)2 complexes. Bipyridyl ruptures the NCX bridge and forms cationic-anionic [M(bipy)3][(NCS)(NCSe)HgR]2 complexes. 相似文献
62.
E.p.r. spectra of [Cu(et2dtc)2], Na[Cu(asp/glut)(et2dtc)] and Na2[Cu(asp/glut)(et2dtc)2] in the polycrystalline state have
been recorded and discussed. The complexes display an antiferromagnetic exchange interaction, increasing in the order: Na2[Cu(asp/glut)(et2dtc)2]
< Na[Cu(asp/glut)(et2dtc)] < [Cu(et2dtc)2]
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
63.
64.
65.
66.
67.
Summary Triisopropoxy bis(O,O-dialkyl dithiophosphates), (i-PrO)3M[S2P(OR)2]2 (M = Nbv, Tav; R = n-Pr, i-Pr, i-Bu and Ph) have been prepared by reacting the appropriate triisopropoxymetal(V)dichloride, (i-PrO)3MCl2 (1 mol) with sodium/ammonium dialkyl dithiophosphates (2 mols)in THF. The monomeric products which are viscous liquids, soluble in common organic solvents and highly susceptible to hydrolysis, were characterized by i.r. and n.m.r. spectra which indicate a bidentate mode of attachment of dithiophosphato groups to the metal. 相似文献
68.
Ghanshyam Pandey 《Tetrahedron letters》2005,46(12):2137-2140
The reactions of alkyl nitriles, acetyl chloride, aldehydes and β-ketoesters or simple ketones was studied for the one-pot synthesis of β-acetamido carbonyl compounds. It was observed that the reaction proceeds in the absence of Lewis acids. However, a Lewis acid catalyzes the reaction and several were tested. It was found that whereas Cu(OTf)2 is suitable for the coupling of β-ketoesters with aldehydes, Sc(OTf)3 is the best for ketones. A possible mechanism is proposed based on the isolation and characterization of an intermediate. 相似文献
69.
B. Pandey M. P. Mahajan R. K. Tikare M. Muneer N. P. Rath P. V. Kamat M. V. George 《Research on Chemical Intermediates》1991,15(3):271-291
The reaction of tetracyclone (1) with potassium in THF gave a mixture of benzoic acid (4), tetraphenylfuran (5) and cis-1,2-dibenzoylstilbene (6). The reaction of 1 with potassium in oxygen-saturated THF gave a mixture of 2-hydroxy-2,4,5-triphenyl-3(2H)furanone (3), 4, 5 and 6, whereas the reaction of 1 with potassium superoxide gave a moderate yield of 3,4,5,6-tetraphenyl-2-pyrartone (7), besides 3, 4, 5, and 6. The reaction of tetraphenylfuran (5) itself with potassium in THF gave a mixture of 6, 1,2,3,4-tetraphenylbutan-1-one (9), 2,3-diphenyl-1-indenone (10) and 2,3-epoxy-4-hydroxy-2,3,4-tnphenyltetralone-l (11), whereas practically no reaction occurred on treatment of 5 with potassium superoxide. Treatment of 10 with potassium in THF, however, gave a mixture of 4, dibenzo[a,c]-13-fluorenone (13), 2,3-diphenyl-2-hydroxyl-1-indanone (14) and 2,3-diphenylbenzofuran (15). A similar mixture of products consisting of 4, 13, 14 and 15 was obtained when the reaction of 10 with potassium was carried out in oxygen-saturated THF or when 10 was treated with potassium superoxide. Treatment of 2,3-diphenyl-2,3-epoxy-1-indanone (16) with potassium on the other hand, gave 10 in excellent yield. Cyclic voltammetric studies have been carried out to measure the reduction potentials of 1, 5, 10 and 16 in the generation of their radical anions. The radical anions of 1, 5, 10 and 16 were also generated pulse radiolytically in methanol and their spectra showed absorption maxima in the region 320–380 nm. 相似文献
70.
B. N. Pandey 《Annals of the Institute of Statistical Mathematics》1979,31(1):225-233
Summary Consider a normal population with mean μ and variance σ2. We are interested in the estimation of population variance with the help of guess value σ
0
2
and a sample of observations. In this paper, a double stage shrinkage estimator
based on the shrinkage estimatorks
1
2
+(1-k)σ
0
2
ifs
1
2
∈R and the usual estimator
ifs
1
2
∋R, whereR is some specified region, have been proposed. The expressions for bias and mean squared error have been obtained. Comparison
with the usual estimators
2 have been made. It was found that though the largest gain is obtained fork=0, we can use
with 0≦k≦1/2 even when σ2 is very close to σ
0
2 相似文献