J. G. H. Du Preez

Complexes of Oxorhenium(V) with Aromatic 2-Amino-Alcohols

Monooxo complexes of rhenium(V) with 2-aminophenol and some of its derivatives (H2nod), containing the N,O donor-atom set, have been synthesized. Square-pyramidal complexes [ReO(nod)2]− were isolated by reaction with (n-Bu4N) [ReOCl4] in ethanol. In benzene the neutral species [ReOCL(Hnod)2] were obtained. In the presence of hydrochloric acid in ethanol, the anionic complexes (n-Bu4N) [ReOCl3(Hnod)] were produced. Trans-[ReOCl3(PPh3)2] was also reacted with some of the H2nod ligands to yield [ReOCL2(Hnod)(PPh3]. The crystal structure of [ReOCl2(Hmap)(PPh3)] (H2map = 2-aminobenzylalcohol) was determined; crystals are monoclinic, P21/n, with a = 15.065(6), b = 11.253(7), c = 15.850(7) Å, β = 94.27(4)°, U = 2680(2) &Aringsup3; and Z = 4. The structure was solved by the Patterson method and refined by full-matrix least-squares techniques to R = 0.042. The monoanionic Hmap− ligand is coordinated as a bidentate through a neutral amino nitrogen and an anionic alcoholate oxygen atom, with the latter trans to the oxo group.

NUCLEOPHILIC ADDITION OF WATER AND ETHANOL TO COORDINATED DI-(2-PYRIDYL)KETONE IN RHENIUM(V) AND TECHNETIUM(V) COMPLEXES. THE CRYSTAL STRUCTURE OF DICHLORO(HYDROXY-DI-(2-PYRIDYL)METHOXIDE)OXORHENIUM(V)

Abstract Complexes of general formula MOCl2[(C5H4N)2C(O)(OR)] (M = Re, Tc; R = H, Et) were prepared by the reaction of trans-ReOCl3(PPh3)2 and (n-Bu4N)[TcOCl4] with di-(2-pyridyl)ketone (DPK) in ethanol (R = Et) under nitrogen and in benzene, containing trace amounts of water, in air (R = H). The compounds were characterized by elemental analysis, vibrational, optical and proton nuclear magnetic resonance spectroscopy. The evidence suggests that the coordinated DPK ligand has undergone addition of water and ethanol at the carbonylic carbon atom, and that the (C5H4N)2C(o)(OR) moiety acts as a uninegative, terdentate N,O,N-donor ligand. The X-ray crystal structure of the complex ReOCl2[(C5H4N)2C(O)(OH)] is also reported. Crystal data: C11H9N2O3Cl2Re, orthorhombic, space group Pcca; a = 14.935(5), b = 11.896(8), c = 14.937(11)A, and U = 2653.8 (2.7)A3 to give Z = 8 for D calc = 2.37 g cm−3. The structure was solved by Patterson and Fourier methods and refined by least-squares methods to R = 0.076. The comple...

Synthesis and Characterization of Bisubstituted Rhenium(V) OXO Complexes with Benzimidazolylalcohol Ligands Containing the N,O Donor-Atom Set

Abstract The reaction of the complex trans-ReOCl3(PPh3)2 with potentially bidentate N,O-donor benzimidazolyl-alcoholate ligands (HL) in the presence of triethylamine in ethanol and benzene produces the complexes ReO(OEt)(L)2 and ReOCl(L)2, respectively. These compounds were characterized by elemental analysis, NMR, vibrational and optical spectroscopy. Mechanisms for the formation reactions and probable configurations of the complexes are proposed, and these are supported by qualitative and spectroscopic studies.

The chemistry of uranium. Part 23. Isomorphous tetrachlorobis(hexamethylphosphoramide)uranium(IV) and tetrabromobis(hexamethylphosphoramide)uranium(IV)

The structures of UCl 4 ·2hmpa and UBr 4 ·2hmpa have been determined by Fourier methods from single-crystal X-ray diffraction data Full-matrix least-squares refinement yielded final conventional R factors of 0.062 and 0.059 respectively. The complexes are isomorphout and crystallise in the space group P2 1 /n with a = 14.141(5), b = 10.530(5), c = 9.076(5) A , β = 93.33° and a = 14.348(5), b = 10.698 (5), c = 9.304(5), β = 91.95 respectively. The hmpa moieties are in trans-octahedral arrangement about the uranium atom. The principal bond lengths are U—X (X = Cl, Br) = 2.615, 2.78; U—O = 2.23, 2.18; O—P = 1.50, 1.53 A respectively.

Some complexes of oxovanadium(IV)

Abstract Complexes of the type VOX2.2L (X = Cl−, Br− and NO3− and L = a monodentate amide ligand) as well as VOI2.5DMSO (DMSO = dimethylsulphoxide) and VOCl2.2.5CH3CN have been prepared in non-aqueous media. these compounds were all characterised by means of ultraviolet, infrared spectroscopy and conductivity measurements in non-aqueous medium.

The chemistry of uranium—VIII: Nitrate as a ligand towards uranium(IV)

Abstract The behaviour of NO 3 − as anionic ligand towards U(IV) in the presence of various amounts of hexamethylphosphoramide was studied in non-aqueous media by conductometric and spectroscopic methods. Various simultaneous equilibria were indicated in solution and conditions were established under which solid nitrato complexes, which differ in stoichiometry, can be isolated. The coordination modes of the nitrato groups were identified by means of i.r. spectroscopy. The donor action of nitrate towards uranium(IV) was compared to that of chloride.

The separation of rhodium and iridium. II. Chloridation and chlorination of iridium(III) and (IV)

Abstract The chloridation of iridium(III) chloro aquo complexes was studied at different aqueous HCl concentrations and temperatures to determine the optimum conditions which upon chlorination will lead to the most convenient method to produce an aqueous solution which only contains the [IrCl6]2− species required for very efficient separation of iridium from rhodium by separating agents like quaternary ammonium species. The interdependency of the two processes of chloridation and chlorination is indicated.

Complexes of technetium(V) with potentially tridentate Schiff bases derived from S-methyldithiocarbazate

Abstract The syntheses and characterization of several new neutral oxotechnetium(V) complexes with potentially dianionic tridentate Schiff bases, derived from S-methyldithiocarbazate, are described. For a 1:1 metal ion to ligand ratio the five-coordinate complexes TcOLCl were isolated in all cases. Only in one case could a six-coordinate TcOL2Cl, with the ligand acting as a bidentate chelate, be isolated from a 1:2 metal ion to ligand ratio. Magnetic susceptibility measurements of the complex TcO(HAF)Cl surprisingly indicate paramagnetism with a d2 electronic configuration, while all the other compounds were found to be diamagnetic. The relative strength of the Tc=O bond is mainly determined by the electronic influence of the cis-ligands. The complexes have been characterized by elemental analyses, infrared and electronic spectra, and conductance measurements.

POLYNITROGEN REAGENTS IN METAL SEPARATION. PART 1. DITERTIARY AND DIQUATERNARY AMMONIUM EXTRACTANTS FOR COBALT(II) AND COPPER(II) IN HCl MEDIUM.

Abstract A variety of alkyldiammonium extractants (tertiary and quaternary)were prepared, characterised and used to extract cobalt(II) and copper(II) from HCl medium. These extractants were compared with Aliquat-336 and Alamine-336. The diammonium derivatives of ethylene diamine proved to be superior to their mono analogues.

Synthesis and Structural Characterization of Dinuclear Oxorhenium(V) Complexes with Bidentate Imidazole Derivatives

The oxo-bridged dinuclear complexes [(μ-O){ReOCl2(L)}2] [L = 2-(1-ethylaminomethyl)-1-methylimidazole (eami); 2-(1-methylaminomethyl)-1-methylimidazole (mami); 2-(1-ethylthiomethyl)-1-methylimidazole (etmi)] were prepared by reaction of trans-[ReOCl3(PPh3)2] with L in acetone. X-ray crystallographic studies of the eami and etmi complexes show that these ligands coordinate in a bidentate manner, and that the cis, cis-N2Cl2 and cis, cis-NSCl2 equatorial planes are nearly orthogonal to the O=Re-O-Re=O backbone.