Solvent Extraction of Niobium and Tantalum. V. Separation of Niobium and Tantalum with TOA and Some N-Substituted Long Chain Amines

Separation of niobium and tantalum by solvent extraction with di-n-octylami no eth anol (DOAE), di-n-octylamino propanol (DOAP), di-n-octylamino butanone (DOAB), di-n-octylamino acetic acid (DOAA), di-n-octylamine (DOA) and tri-n-octylamine (TOA) in chloroform is described, in the metal concentration ra n ge of 10-5 M. Separation can be a chieved in 0.2 M HF metal solutions in the sulphuric acid concentration range of 1-5 M. Tantalum is extracted into the organic phase and can be stri pped back easily with 1-6 M hydrochloric acid. Niobium and tantalum of radiochemical purity are obtained. The separation factors displayed by these extraction reagents are compare d and discussed

A Folded Conformation of 1,4,8,11-Tetrathiacyclotetradecane in its Mercury Compound: l,4,8,11-Tetrathiacyclotetradecanedipicratomercury( II) Heminitromethane, [Hg(C10H20S4)· (C6H2N307)2] · 1/2CH3N02

The crystals of 1,4,8,11-tetrathiacyclotetradecanedipicratomercury( II) heminitromethane, [Hg(C10H20S4) · (CsH2Ns01h] · 1/2CHsN02, are triclinic, spcrce group Pl with a = 1.2794(6), b = 1.3108(5), c = = 1.0090(3) nm, a= 92.85(3) 0 , fJ = 107.67(3)0 , y = 94.54(4) 0 , V = 1.60236 nm3, and Z = 2. The structure was solved by the heavy atom method and refined by the least-squares method to R = 0.030 for the 7321 unique reflections. It consists of discrete, well separated molecules. Coordination of the mercury atom is a distorted octahedron with four sulfur atoms (Hg-S distances are 245.8(1), 251.9(1), 262 .. 9(2), and 305.0(2) pm) from the macrocycle and two oxygen moms (Hg-0 distances are 253.1(3) and 255.8(3) pm) from the two picrates. The macrocycle is folded so that three sulfur atoms with short Hg-S bonds are in an equatorial and the fourth in an apical position. The conformation of the coordinated macrocycle is compared to the conformation of cyclotetradecane at 116 K and to the conformation of the free crysta-lline macrocycle

Tungsten(VI) and molybdenum(VI) complexes with soft thioether ligand coordination: synthesis, spectroscopic and structural studies

Reaction of WX6 (X = Cl or Br) with O(SiMe3)2 in CH2Cl2, followed by addition of MeCN and a further equivalent of O(SiMe3)2 in CH2Cl2 gives [WO2X2(MeCN)2] in situ, which subsequently react with the dithioethers MeS(CH2)2SMe, iPrS(CH2)2SiPr or 1,4-dithiane to afford the first series of WVI thioether complexes, [WO2X2(dithioether)]. The very moisture-sensitive yellow complexes have been characterised by microanalysis, IR, 1H and 13C{1H} NMR spectroscopy, which indicate cis-dioxido and trans-dihalide arrangements in the monomers with two thioether donor atoms completing the very distorted octahedral geometry (confirmed by a crystal structure of [WO2Cl2{iPrS(CH2)2SiPr}]). The strongly polymerised WO2X2 compounds themselves are not useful synthons for the preparation of the WVI thioether complexes and substitution of the dimethoxyethane ligand in [WO2Cl2{MeO(CH2)2OMe}] by dithioethers is also incomplete. Molybdenum(VI) dioxidodichloride thioether complexes of the form [MoO2Cl2(L)] (L = iPrS(CH2)2SiPr, 1,4-dithiane, 2-[15]aneS2O3, 2-[14]aneS4 and 2-[12]aneS4) ([15]aneS2O3 = 1,4-dithia-7,10,13-trioxacyclopentadecane, [14]aneS4 = 1,4,8,11-tetrathiacyclotetradecane, [12]aneS4 = 1,4,7,10-tetrathiacyclododecane) and the unusual dinuclear [Mo2O4Cl4{o-C6H4(CH2SMe)2}2] are obtained by direct treatment of MoO2Cl2 with the appropriate ligand. The [Mo2O4Cl4{o-C6H4(CH2SMe)2}2] adopts an unexpected metallocyclic structure with cis-MoCl2 units and bridging bidentate dithioether (confirmed crystallographically). The structure of a new polymorph of [WO2Cl2{MeO(CH2)2OMe}] is also described