New neutral and cationic cyclopentadienylcobalt complexes

The treatment of the aquocation [Co(η3-2-MeC3H4)(η5-C5H5)(H2O]+ with neutral and anionic ligands gives new cobalt complexes containing cations [Co(η3-2-MeC3H4)(η5-C5H5)L]n+, n = 0; L = CN, CH3COO, CF3COO and n = 1; L = P(p-MePh)3, NCEt, NCPh, CNCy, dppm and [{Co(η3-2-MeC3H4)(η5-C5H5)}2 (μ-L-L)]2+, L-L = bipy, dppm. The neutral cyano complex reacts with various electrophiles to give cationic isocyanide complexes containing the cation [Co(η3-2-MeC3H4)(η5-C5H5)(CNR)]+, which have been isolated in low yields. Chemical behaviour and structural implications of IR and 1H and 13C NMR spectra are discussed.The authors greatly appreciate financial support from the Comisión Asesora de Investigación Científica y Técnica. Ref. 2001/83. Spain

New η-allyl η-cyclopentadienylcobalt cations

[Co(R-η-C3H4)(η-C5H5)I] is a good precursor for the preparation of some new cationic complexes as the iodide can easily be replaced; thus addition of PEt3 to the iodo-complex (R  H) gives [Co(η-C3H5)(η-C5H5)(PEt3)]+. The reactions of [Co(R-η-C3H4)(η-C5H5))I] (R  H or 2-Me) with AgBF4 give solutions containing the coordinatively unsaturated species [Co(R-η-C3H4)(η-C5H5)+. The presence of traces of water leads to the formation of [Co(R-ηC3H4)-(η-C5H5)(H2O)]+. The addition of monodentate ligands L  PEt3 PPh3, AsPh3, SbPh3, CNCH3 and bidentate ligands LL  Ph2PCH2CH2PPh2(dppe) and o-C6H4(AsMe2)2(diars), gives, respectively mononuclear [Co(2-Me-ηC3H4)-(η-C5H5)L]+ and binuclear ligand-bridged [(2-Me-ηC3H4)(η-C5H5)CoLLCo(2-Me-ηC3H4)(η-C5H5))]2+ complexes. Crystals of [Co(2-Me-ηC3H4)(η-C5H5)-(H2O)]+[BF4]- are monoclinic, space group P21/c, with a 7.858(3), b 10.262(4), c 15.078(4) Å, β 98.36(1)°. The molecular structure contains the cobalt atom bonded to planar 2-Me-allyl and cyclopentadienyl substituents, which are almost parallel with the H2O molecule in a staggered conformation with respect to the 2-Me group.Comisión Asesora de Investigación Científica y Técnic

Extractive spectrophotometric determination of cobalt using xanthates

342-343The 1:3 (metal-ligand) complexes of cobalt with various xanthates are extractable into chloroform and show linear response upto 5 ppm of cobalt when the absorbance is measured at 355 nm. The molar absorptivities and Sandell's sensitivities of the complexes are in the ranges (0.98-1.65) x 1041 mol-1cm-1 and 0.006-0.004 μg Co/cm2 respectively

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Not AvailableInitial studies in the germplasm of cultivated groundnut using RFLP and RAPD revealed very limited polymorphism (Kochert et al., 1991, Halward et al., 1992) and led to the opinion that cultivated groundnut has a very narrow genetic base. However, the studies by He and Prakash (1997) indicated the possibility of exploiting DAF and AFLP techniques for the detection of polymorphism in groundnut. In the present study, Amplified Fragment Length Polymorphism (AFLP) was done using 64 combinations of primers specific to EcoRI and Mse I with the selective nucleotides in 12 groundnut cultivars. Primer combinations were ranked based on their ability to amplify different fragments, and having more than 10% polymorphism and selected five primer pairs. These primer pairs were further tested in four genotypes viz. TMV 7, Chandra, RS 1 and UF 70-103 for confirmation. All the selected primers could give amplification of the fragments and the banding pattern showed polymorphism. The five primers when tested with cultivars which are selections from Robut 33-1, also shown polymorphism.It could be concluded that the five primers selected were suitable for detecting polymorphism and can be further used in varietal identification and finger printing, and to tag genes of economic importance in breeding programmes.Not Availabl