Jan G.H. du Preez

The reactivity of the [Re≡O]3+ core toward aromatic 1,2-diamines: the formation of rhenium(V)-imido complexes

The reaction of the aromatic diamines 1,2-diaminobenzene, 2,3-diaminophenol (H 2 L), 2,3-diaminotoluene and 3,4-diaminobenzophenone (H 2 NRNH 2 ) with trans -ReOCl 3 (PPh 3 ) 2 in an equimolar ration in ethanol gave the products trans -[Re(NRNH 2 )Cl 3 (PPh 3 ) 2 ] in good yield. IR 3 H NMR and X-ray crystallographic results indicate that the diamine ligands coordinate to rhenium(V) in a dianionic monodentate imido form. The structure of trans -[Re(L)Cl 3 (PPh 3 ) 2 ] was determined and shows that only the deprotonated amino nitrogen in the 2-position of the potentially ambidenatate 2,3-diaminophenol molecule is coordinated to the metal.

The coordination mode of 3-hydroxypicolinic acid in oxorhenium (V) complexes. Crystal and molecular structures of (n-Bu4N) [ReOCl3 (HOC5H3NCO2)] and [ReOCl(HOC5H5NCO2)2]

The reaction of (n-Bu 4 N)[ReOCl 4 ] with 3-hydroxypicolinic acid (HL 1 ) in benzene and ethanol yields the green (n-Bu 4 N) [ReOCl 3 (L 1 )] ( 1 ) and blue [ReOCl(L 1 ) 2 ] ( 2 ) complexes, respectively. Elemental analysis, infrared. 1 H NMR and conductivity results indicate that the ligand L 1− acts as a monoanionic bidentate N,O -donor chelate in these complexes. Complexes 1 and 2 were also characterized by X-ray crystallography. Crystal data: C 22 H 40 Cl 3 N 2 O 4 Re ( 1 ): monoclinic space group P 2 1 / n , a = 8.111(3), b = 20.842(8), c = 16.722(7)A, β = 98.14(3)°, V = 2794(2)A 3 , Z = 4, D calc = 1.638Mg m −3 ; structure solution and refinement based on 2451 reflections (Mo Kα, λ = 0.710 73A) converged at R = 0.044. C 12 H 8 ClN 2 O 7 Re ( 2 ): monoclinic space group P 2 1 / n , a = 7.923(3), b = 10.681(5) c = 16.539(7)A, β = 97.80(3)°, V = 1387(7)A 3 , Z = 4, D calc = 2.461Mg m −3 ; 1899 reflections, R = 0.069.

Synthesis and characterization of technetium(V) and (VII) complexes with bidentate nitrogen donor ligands. X-ray molecular structures of tetrabutylammonium bis(1,2-diimidobenzene)oxotechnetium(V) and tris(1,2-diimidobenzene)technetium(VII) pertechnetate

Abstract The reaction of pertechnetate with 1,2-diaminobenzene (H2pda) in the presence of the reducing agent sodium dithionite in alkaline aqueous solution led to the formation and isolation of (n-Bu4N)[TcO(pda)2] (1). If the reaction is performed without reducing agent in methanol, the green compound [Tc(pda)3](TcO4) (2) is formed. Both complexes are diamagnetic, and a single NH stretching frequency in both indicates that each pda ligand contains one hydrogen per nitrogen, and is dianionic. X-ray crystal structures of both compounds are also reported. Crystal data for complex 1, C28H48N5OTc: orthorhombic, space group P212121, a=11.644(3), b=15.303(4), c=16.950(5) A and U=3020.3(1.5) A3 to give Z=4 for Dcalc=1.25 g cm−3. Crystal data for 2, C18H18N6O4Tc2: orthorhombic, Pna21, a=13.869(4), b=12.799(5), c=10.851(3) A and U=1926.2(1.1) A3 to give Z=4 for Dcalc=1.99 g cm−3. The structures have been solved by Patterson and Fourier methods and refined by least-squares methods to R=0.058 for 1 and 0.090 for 2. Complex 2 represents the first tris-bidentate cationic complex of technetium to be structurally characterized. Complex 1, with an unexpectedly low ν(TcO) of 891 cm−1, has a TcO bond distance of 1.668(7) A, that is typical for monooxotechnetium(V) square-pyramidal complexes.

NITROGEN REAGENTS IN METAL ION SEPARATION. XI. THE SYNTHESIS AND EXTRACTION BEHAVIOR OF A NEW NS IMIDAZOLE DERIVATIVE

A new extractant with an NS donor chromophore viz. 2-(1-ethylthiomethyl)-1-decyl imidazole (ETDIMZ) has been synthesized. Its extraction behavior towards each of Co2+, Ni2+, Cu2+, and Zn2+ in each of perchlorate, chloride and thiocyanate media in dilute acid media have been studied. Its behavior was compared with a similar pyridine derivative, viz. 2-(octylthiomethyl)-pyridine (OTMP) under comparable conditions. These behaviors have been interpreted in terms of the coordination chemistry of the metal ions. It was shown how formation constants of simple ligands, symmetry of the complex species and phase transferability can influence extraction behavior and how the above parameters can assist in the development of metal ion specific extractants.

The chemistry of uranium. Part 35. Synthesis and characterization of UI4L2 complexes (L = bulky amide ligands) and the crystal structure of UI4tmu2 (tmu = tetramethylurea)

Abstract A number of trans-octahedral complexes of uranium tetraiodide have been isolated for the first time using bulky CO amide ligands. The solid reflectance electronic spectra of these complexes indicated a shift in the major peaks of their spectra to higher energies with reference to the of UI62−. The infrared spectra of the substituted complexes showed a reverse of the position of the CO stretching frequencies and the NCN stretching frequencies upon complexation, indicating the high Lewis acidity of UI4. The structure of UI4tmu2 has been determined by X-ray crystallography. The compound crystallized in the orthorhombic system, space group Pbcn. Cell constants are: a = 11.480(5), b = 14.657(5), c = 13.453(5) A; Dc = 2.87 g cm−3. There are four independent molecules of the compound in the unit cell with uranium, oxygens and their attached carbon atoms lying on the two-fold symmetry axis. The uranium atom is trans-octahedrally surrounded by meridional iodide ions and apical oxygen atoms of tmu groups. The OUO sequency is linear. Selected mean bond lengths are: UI 3.01 A, UO 2.185 A, CO 1.29 A. A comparison was made between the UX4tmu2 structures (X = Cl, Br and I). UI4tmu2 proved to be much more thermally unstable than its chloro and bromo analogues.

RECENT ADVANCES IN AMINES AS SEPARATING AGENTS FOR METAL IONS

ABSTRACT In this article those aspects of the application of amines in metal ion separation during the last two decades which could be regarded as new facets or as clarifying earlier concepts have been briefly dealt with. This includes work with diammonium extractants and a comparison with their monocationic analogues and new approaches to explain the different secondary effects. In addition more emphasis has been placed on the neutral N-donor action of amines and their application towards metal ion specificity. The importance of a thorough understanding of the basic properties of the amine and the metal ion were indicated for the development of new metal ion specific separating agents.ABSTRACT In this article those aspects of the application of amines in metal ion separation during the last two decades which could be regarded as new facets or as clarifying earlier concepts have been briefly dealt with. This includes work with diammonium extractants and a comparison with their monocationic analogues and new approaches to explain the different secondary effects. In addition more emphasis has been placed on the neutral N-donor action of amines and their application towards metal ion specificity. The importance of a thorough understanding of the basic properties of the amine and the metal ion were indicated for the development of new metal ion specific separating agents.

Nucleophilic addition of water to coordinated di-(2-pyridyl)ketone (DPK) in rhenium(V) complexes. Synthesis and crystal structure of the adduct (DPK·H)+[{ReOCl2(DPK·OH)}2Cl]−

The crystalline adduct of formula (DPK·H)+[{ReOCl2(DPK·OH)}2Cl]− was prepared by the reaction of trans- ReOCl3(PPh3)2 with di-(2-pyridyl)ketone (DPK) in THF or dichloromethane. The compound was characterized by elemental analysis, vibrational, optical and 1H NMR spectroscopy. The evidence suggests that the coordinated DPK ligands have undergone addition of water at the carbonylic carbon atom, and that the (C5H4N)2C(O)(OH) moiety acts as a uninegative, terdentate N,O,N-donor ligand. The X-ray crystal structure of the compound is also reported. Crystal data: C33H27Cl5N6O7Re2, triclinic, space group P1; a=9.483(3), b=14.399(5), c=15.413(7) A, α=110.68(3), β=104.73(3), γ=92.66(3)° and U=1879.9(9) A3 to give Z=2 for Dcalc=2.07 Mg/m3.

The coordination chemistry of divalent cobalt, nickel and copper. Part 8. Selected complexes containing N-substituted pyridine-2,6-dicarboxamide ligands; crystal structure of dibromo(N,N′-dimethyl-N,N′-diphenylpyridine-2, 6-dicarboxamide)nickel(II)

Abstract Diverse complexes of divalent cobalt, nickel and copper and the ligands N,N,N′,N′-tetramethylpyridine-2,6-dicarboxamide (tdpa), N,N′-dimethyl-N,N′-diphenylpyridine-2,6-dicarboxamide (dpda) and N,N,N′,N′-tetraisopropylpyridine-2 ,6-dicarboxamide (ppda) were discussed in order to illustrate the properties of these ligands. The complexes [M-(ppda)2](ClO4)2 (M = Co, Ni and Cu) and [Co-(ppda)2] (ClO4)2(acet) (acet = acetone), had distorted octahedral chromophores. The distortion was most pronounced in [Cu(ppda)2](ClO4)2. This severe distortion was not present in octahedral [Ni(tdpa)2]-(CIO4)2. Isostructural, crystalline (MCl2)3(tdpa)12 (M= Ni and Co) were isolated from hot solutions. The solid reflectance spectra were resolved into gaussian components. This data, in conjunction with infrared and magnetic measurements, enabled the assignment of the formula [MCl(tpda)]2[MCl4] to these complexes. The anion was found to be tetrahedral while the cation had a distorted tetrahedral chromophore. The reaction of NiBr2 with dpda produced two complexes; green αNiBr2(dpda) was isolated at room temperature while red βNiBr2(dpda) was obtained from hot solution. Characterisation data indicated αNiBr2(dpda) to have a pentacoordinate chromophore. The characterisation data for βNiBr2(dpda) was ambiguous and a crystal structure determination was performed (monoclinic crystal, space group P21/a with a = 13.871, b = 16.019, c = 9.878A, β = 95.492°, final R factor = 0.0549 and Nobs = 2221). The Ni was in a distorted square pyramidal environment with the donor atoms of dpda and a bromine atom constituting the basal plane and the remaining bromine atom occupying the apical position. The coordination spheres of the crystalline complexes NiBr2(dpda)(dmp) (dmp = 2,2-dimethoxypropane) and NiBr2(dpda)(acet) were analogous to those of αNiBr2(dpda) and βNiBr2(dpda) respectively.

The reaction of nitro-1,2-diaminobenzenes with the [ReO]3+ core: isolation of oxo-free rhenium(V) complexes

Abstract The reaction of 2 equiv. of 3-nitro-1,2-diaminobenzene (H2L1) with trans-ReOCl3(PPh3)2 in ethanol gave the oxo-free rhenium(V) complex [ReCl(PPh3)(L1)2] (1) in good yield. IR, 1H NMR and X-ray crystallographic results indicate that the diamine ligand L1 coordinates in a dianionic bidentate diamido form to the metal, and that the complex has the unusual skew-trapezoidal bipyramidal geometry. With 4-nitro-1,2-diaminobenzene (H2L2) as ligand the complex [Re(L2)Cl3(PPh3)2] (2) was characterized, in which L2 coordinates in a dianionic monodentate imido form through one nitrogen only. Crystal data for 1·EtOH: C32H31ClN6O5PRe, monoclinic P21/c, a=14.937(11), b=15.017(8), c=15.394(12) A, β=112.12(6)°, V=3198.7(38) A3, Z=4, Dcalc=1.728 g cm−3, structure solution and refinement based on 3151 reflections converged at R=0.0807.

Synthesis and structure of the first neutral octahedral cis-dioxorhenium(V) complex

The complex cis-[ReO2(Hdab)(py)2] (1) (H2dab=1,2-diaminobenzene) has been prepared by reacting trans-[ReO2(py)4]I with H2dab in ethanol. This is the first example of a neutral hexacoordinate rhenium(V) complex with a cis arrangement of the two oxo groups. The compound also provides the first example of a bidentate monoanionic monoimino coordination mode of H2dab. Crystal data for 1·(H3dab)I·H2O: C22H26IN6O2Re·H2O, triclinic, space group P1, a=9.570(2), b=12.493(3), c=12.851(3) A, α=61.60(3), β=70.56(3), γ=78.68(4)°, V=1273.1(4) A3 and Z=2.