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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.

Reactions of trans-[ReO2(py)4Cl] and cis-[ReO2I(PPh3)2] with 2,3-diaminophenol (H2dab-OH) and 1,2-diaminobenzene (H2dab), respectively, in ethanol under aerobic conditions led to the corresponding isolation of [Re(sbqdi-OH)3]Cl (1) and [Re(sbqdi)3]I (2). Crystallographic data show that the ligand sbqdi represents the monoanionic N,N-coordinated π-radical form of the 1,2-benzosemiquinone diimine of H2dab. The ligands in Complex 1 clearly show semiquinoid character; e.g., the two C-N and two Re-N bondlengths differ considerably. In 2, the phenyl rings display typical quinoid distortions with two localized double bonds, and the C-N bondlengths are short, approaching double bonds. Rhenium is formally in the +IV oxidation state.

The reaction of cis-[ReOCl2(L3)] (L3− = terdentate O, N, N-donor ligand 2-[[{2-(2-pyr-idinyl)ethyl}amino]methyl]phenolate) with ethylene glycol (H2eg) in acetonitrile led to the isolation of [ReO(L3)(eg)]. The analogous complexes [ReO(L3)(cat)] (H2cat = 1, 2-dihydroxybenzene) and [ReO(L3)(ox)] (H2ox = oxalic acid) could not be prepared by this method. [ReO(L3)(cat)] was synthesized by the one-pot reaction of [ReOCl4 −] with a twofold molar excess of HL3 and H2cat in ethanol, and [ReO(L3)(ox)] was isolated from the reaction of [ReO(L3)(eg)] and H2ox in acetonitrile. All complexes were characterized by various physical techniques, including IR and NMR. The X-ray crystal structure of [ReO(L3)(cat)l/2EtOH] was determined. Crystals are triclinic, P, a = 8.920(2), b = 11.209(5), c = 11.735(5)A, α = 78.00(4), β = 68.93(3), γ = 86.49(3)°, Z = 2. The structure was solved by the Patterson method and refined by full-matrix least-squares procedures to R = 0.047 (Rw = 0.066) for 2321 reflections with F 0 > 3[...

Monooxo complexes of rhenium(V) with 2-[[[(2-pyridinyl)ethyl]amino]methyl]phenol (HL2) and some of its derivatives, containing the ONN donor-atom set, have been synthesized. The complexes with general formula [ReOCl2(Ln)] were characterized by various physical techniques, including IR and NMR. X-ray structures of [ReOCl2(Ln)] (n = 2,3,5; HL3 = 2-[[[2-(dimethylamino)ethyl]amino]methyl]phenol; HL5 = 2-[[(2-pyr-idinylmethyl)ethylamino]methyl]phenol) were determined. Crystals of [ReOCl2(L2)] (2) are rhombohedral, R3, a = 13.915(2)A, α = 81.76(2)°, Z = 6; those of [ReOCl2(L3)] (3) are monociinic, C2/c, a = 25.92(2), b = 9.426(8), c = 28.38(2)A, β = 100.33(9)°, Z = 16. [ReOCl2(L5)], (5), is monociinic, P21, a = 7.380(4), b = 11.743(7), c = 8.346(5)A, β = 94.74(5)°, Z = 2. The structures were solved by the Patterson method and refined by full-matrix least-squares to R = 0.038, 0.036 and 0.062 for complexes 2, 3 and 5, respectively. In all three complexes the multidentate Ln − ligands act as terdentate O...

The reaction of the complex [ReOCl2(HL)(PPh3)] (1; H2L = 2,6-bis(hydroxymethyl)pyridine), in which HL− acts as a bidentate monoanionic N,O−-donor ligand, with the potentially bidentate N,O−-donor ligands N-phenylsalicylideneimine (PhsalH) and 8-hydroxyquinoline (oxineH) in ethanol led to the substitution of the chelate HL− to produce trans-[ReOCl2(Phsal)(PPh3)] (2) and trans-[ReOCl2(oxine)(PPh3)] (4). In benzene the mixed bis(bidentate) ligand complexes [ReOCl(Phsal)(HL)] (3) and [ReOCl(oxine)(HL)] (5) were isolated. Complex 1 also reacts with a molar excess of PhsalH and oxineH(NOH) in ethanol to form ReOCl(NO)2. All the complexes were characterized by various physical techniques, including IR and NMR. X-ray structures of 2 (C31H25Cl2NO2PRe) and 5 (C16H14ClN2O4Re) were determined. Crystals of 2 are triclinic, P 1, a = 8.813(4), b = 10.200(4), c = 16.913(7) A, α = 84.90(3), β = 80.81(3), γ = 67.44(3)°. Z = 2; those of 5 are monoclinic, P21/c, a = 14.091(2), b = 8.171(2), c = 15.227(2) A, β = 115....

The interaction of 2-amino-1-cyclopentene-1-dithiocarboxylic acid, and its N-and S-alkyl derivatives (HL2), with rhenium(V) and technetium(V) was investigated. Complexes of formula MOCl(L2)2 (M = Tc, Re) were isolated from the reaction of (n-Bu4N)[MOCl4] with a twofold molar excess of HL2, in acetone, at room temperature. Compounds of type ReOCl2(L2)(PPh3) were characterized with trans-ReOCl3(PPh3)2 as starting material in ethanol. In all the complexes L2 − acts as a bidentate NS− -donor ligand. Infrared and 1H n.m.r. data were used to establish the tautomeric forms of the ligands L2 − in the complexes.

The complexes trans-ReOCl3(PPh3) (HL′) · Me2CO [HL′ = 2-(N-ethylamino)-1-cyclopentenedithio-carboxylate and 2-(N-cyclohexylamino)-1-cyclopentenedithiocarboxylate], with the ligand HL′ coordinated as a monodentate to rhenium(V) through the neutral thiocarbonyl sulfur atom in the position trans to the PPh3 molecule, were prepared under reflux conditions in acetone by the reaction of trans-ReOCl3(PPh3)2 with a molar excess of HL′. The products were isolated as light green precipitates from reaction solutions immediately after cooling to room temperature. The compounds cis-ReOCl3(PPh3) (HL′) · Me2CO were isolated as dark green crystals from the filtrate on slow evaporation of the solvent at room temperature over a period of 2 days. Physicochemical, infrared, 1H NMR and spectroscopic data are reported.

Complexes formed by the reaction of (n-Bu4N)[MOCl4] (M = Re, Tc) with the diimines 2,3-bis(2-pyridyl)pyrazine (DPP) and 2,3-bis(2-pyridyl)quinoxaline (DPQ) in ethanol were studied. With DPP as ligand, the monometallic complexes [MOCl2(X)(DPP)] (M = Tc, Re; X = Cl, OEt) and the bimetallic compounds [MOCl2(X)](μ-DPP) [MOCl2(OEt)] (X = Cl for M = Tc; X = OEt for M = Re) were isolated. Infrared and 1H NMR data suggest that coordination of DPP to the metals occurs in a bidentate manner through one pyrazine and one pyridine nitrogen atom to form a five-membered metallocycle. Only monometallic complexes of formulation [MOCl2(X)(DPQ)] (X = Cl, OEt) could be isolated with DPQ as ligand, irrespective of the mol ratio of reactants. Experimental evidence suggests bidentate coordination of DPQ to the metals through the two pyridinic nitrogen atoms, with the two quinoxaline nitrogens not participating in bonding to the metals, to form a single seven-membered chelate ring.

The complex TcO{(o[sbnd]O[sbnd]C6H4)(CH3) C[dbnd]NN[dbnd]C(S)(SCH3)}{(CH3)2C[dbnd]NN[dbnd]C(S) (SCH3)} was prepared by the reaction of (n-Bu4N) [TcOCl4] in methanol with the Schiff base S-methyl-β-N-(2-hydroxyphenylethylidene)dithiocarbazate in acetone. The compound was characterized by elemental analysis, vibrational and optical spectroscopy, and X-ray crystallography. Crystal data: C15H19N4O2S4Tc, monoclinic, space group P21/c, a = 14.799(5), b = 7.470(2), c = 19.272(5)A, U = 2064.4(1.8)A3, Z = 4, D calc = 1.65 g cm−3. The structure was refined by least-squares methods to R = 0.102. The complex has a Tc=O bond distance of 1.633(8)A, and the deprotonated phenolic oxygen of the terdentate ONS-donor ligand is coordinated trans to the oxo oxygen.

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...

Six-coordinate cationic complexes of rhenium(V) and technetium(V) with the tridentate N-(2-oxidophenyl)-salicylideneiminate (OPhsal2-) and the bidentate aromatic nitrogen-donor ligands 2,2′-dipyridine, 1,10-phenanthroline, 2,2′-dipyridylamine and bis(2-pyridyl)ketone (NN) have been prepared. Complexes of general formula [MO(OPhsal)(NN)]X (M = Re, Tc; X = Cl, PF6) were isolated by the reaction of ReOCl(OPhsal)(PPh3) and TcOCl(O Phsal) with the bidentate nitrogen-donor ligands. The reaction of TcOCl(O Phsal) with bis(2-pyridyl)ketone (dpk) in ethanol produced the complex [TcO(OPhsal)-(dpk.EtOH)]Cl, in which alcoholation of ethanol across the ketone double bond of dpk has occurred. Spectroscopic and analytical results obtained for all the isolated complexes suggest terdentate coordination of OPhsal2- in the equatorial plane cis to the oxo oxygen, with the bidentate pyridyl nitrogen-donor ligands bridging the fourth equatorial site and the position trans to the oxo group.

Cationic square-pyramidal complexes of general formula (TcO(L)+ 2]Cl− were prepared by the reaction of (n-Bu4N)TcOCl4 with the potentially bidentate N,S-donor benzimidazolylthiols (HL) as ligands in the presence of triethylamine. The corresponding reaction with the N,O-donor benzimidazolylalcohols led to the formation and isolation of the neutral six-coordinate complexes TcOCl(L)2. These compounds were characterized by elementalanalysis, vibrational and optical spectroscopy. Mechanisms for the formation reactions and probable configurations of the complexes are proposed on the basis of qualitative studies and spectroscopic results.

Complexes formed by the ligand exchange reactions of [TcOCl4]− with the potentially terdentate nitrogen-donor ligand 2,2′:6′,2″-terpyridine (terpy) under different reaction conditions have been investigated. Both bidentate and terdentate coordination of terpy have been established in the complexes prepared. In dichloromethane as reaction medium the six-coordinate complex TcOCl3(terpy-N,N′) has been isolated, in which terpy acts as a bidentate ligand. The reaction of terpy with a twofold molar excess of [TcOCl4]− in boiling ethanol led to the formation of the cationic six-coordinate complex [TcOCI2(terpy-N,N′,N″)]+, which precipitated from solution as the pertechnetate salt. With terpy in excess to [TcOCI4]− the cationic dimeric complex μ-O[TcOCl(terpy-N,N′,N″)]2Cl2. was isolated in ethanol. The reaction of TcO− 4 with terpy in an ethanolic/HCl solution led to the precipitation of the neutral six-coordinate complex TcOCl3(terpy .HC1), which could also be prepared from [TcOCl4]−. These compounds we...

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 synthesis of these technetium radiopharmaceuticals often requires a prereduction of pertechnetate with sodium dithionite or stannous chloride prior to complex formation. We now describe the product of the reaction between pertechnetate and 2-benzimidazole-2'-ylethanethiol (Hbls). In this reaction, the ligand Hbls serves as an acid to hydrolyze oxo ligands of the pertechnetate ion, as a reducing agent for technetium (VII), and as a chelating agent for technetium (V). The product of this reaction is the cationic complex Tc V O(bls) 2 + , which was isolated as [TcO(bls) 2 ][TcO 4 ] and as [TcO(bls) 2 ] BPh 4

The authors have used the potentially bis(terdentate) nitrogen aromatic heterocyclic ligand 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tppz) to prepare mono- and bimetallic technetium(V) complexes bound to tppz. The stimulus for the development of the coordination chemistry of the man-made element technetium is provided by the use of complexes of this element as anatomical imaging agents in nuclear medicine. Although the chemistry of technetium(V) with nitrogen donor ligands is well understood, no complexes have been prepared using potentially terdentate neutral nitrogen donor ligands of this metal in the +5 oxidation state.

Novel binuclear complexes of heptavalent and pentavalent technetium with the bridging ligand 3,6-bis(2′-pyridyl)-1,2,4,5-tetrazine (bptz) have been prepared and characterized by analysis and optical and vibrational spectroscopy. The heptavalent complexes with the formulation (μ-bptz)[TcO3X]2 (X = Cl, OCH3, OCH2CH3) were synthesized from pertechnetate and the ligand bptz-2HCl in the appropriate alcohol (X = OMe, OEt) or from pertechnetate and bptz in ethanolic aqueous HC1 (for X = Cl). Binuclear complexes of technetium(V) with the formulation (u-bptz)[TcOCl2X]2 (X = OEt, Cl) were prepared in ethanol from TcOCl− 4 and bptz in the absence (X = OEt) and presence (X = Cl) of ethanolic aqueous HC1. The mononuclear technetium(V) complex [TcO2(bptz)2]Cl has also been isolated under certain experimental conditions. Mononuclear complexes of the ligand 4-phenyl-3,6-bis(2′-pyridyl)pyrida-zine (pppz) with formulae TcO3(pppz)Cl and TcO(pppz)Cl3 were prepared from pertechnetate and TcOCl− 4, respectively, with ...

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.

Amino acid Schiff base technetium(V) complexes of salicylaldehyde with l-cysteine, l-serine, l-histidine, l-threonine, l-glutamic acid and l-tryptophan have been prepared by direct reaction and by constituent combination. The amino acid part of the ligands coordinates to the technetium through the carboxylate group, while the other available functional group of the amino acids plays a more minor role as a blocking group or in intramolecular bonding.

The thermal decomposition of Cs2 U(NO3)6 has been investigated. The activation energy for the decomposition reaction was estimated to be ±120 kJ/mole, while the enthalpy of the reaction was calculated as 18 kJ/mole. These energy parameters were compared with similar parameters obtained for the decomposition of Cs2 Th(NO3)6 and U(NO3)4.2hmpa. It indicated that the nitrate ion is primarily responsible for the oxidation of the uranium with atmospheric oxygen having no effect at all. The dissociation reactions involved in the decomposition of M(NO3)4.4hmpa, (M = U and Th), are accompanied by intramolecular rearrangements of the nitrate groups.

Preparation and properties of new cobalt(II) complexes using ligands with OSO sets of donor atoms, viz. bis(N,N-dimethylacetamido)-thioether (TTDA) and bis(N-methyl-N-phenylacetamido)thioether (DTDA), are reported. Magnetic, spectral and non-aqueous conductivity data were obtained. Penta-coordinate structures are proposed for solid CoX2. TTDA (X = Cl−, Br−, I−, NO3 − and NCS-) and CoX2. DTDA (X = Cl−, Br− and NCS-). Similar data for Co(NO3)2. DTDA and Co(ClO4)2. 2TTDA strongly suggest distorted octahedral structures for these. Gaussian analysis on the solid reflectance spectra were done.