Voltammetry of oxorhenium(V) complexes containing the [O=Re−OR] core and substituted pyridine ligands

Compounds of the general formula [ORe(OR)Cl₂(PPh₃)₂] and [ORe(OEt)Cl₂(PPh₃)(py)], where R=alkyl or aryl and py=a substituted pyridine, were synthesized and their voltammetric behaviour investigated. For the former, the electron-transfer mechanism was observed to be dependent on solvent. In dry MeCN, a quasi-reversible oxidation and a reduction followed by a chemical reaction was observed. There were indications of nucleophilic attack on electrochemically generated [ORe(OEt)Cl₂(PPh₃)₂]⁺, forming an unstable species whose reduction potentials were strongly dependent on the identity of the nucleophile. Voltammetric and spectroscopic observations of the oxorhenium(V) alkoxypyridine complex indicate the pyridine to be labile in halogenated hydrocarbon solvents but not in Me₂CO, MeCN, or CCl₄. Electrochemical generation of [ORe(OEt)Cl₂(PPh₃)(Cl_xC_yH_z)]⁺ (x=1,2, or 3; y=1 or 2; z=2,3, or 4) appears to be followed by transfer of a hydrogen atom from the solvent to form [(HO)Re(OEt)Cl₂(PPh₃)]⁺. Various pyridine complexes of this type were preparedvia substitution reactions under mild conditions. Varying the reaction conditions allowed the synthesis oftrans-dioxotetrapyridyl complexes in excellent yield.     

Chelated hydrazido(3-)rhenium(V) complexes: on the way to the nitrido-M(V) core (M = Tc, Re)

Neutral and asymmetrical hydrazido(3-)rhenium(V) heterocomplexes of the type [Re(eta(2)-L(4))(L(n))(PPh(3))] (eta(2)-L(4) = NNC(SCH(3))S; H(2)L(1) = S-methyl beta-N-((2-hydroxyphenyl)ethylidene)dithiocarbazate, 1, H(2)L(2) = S-methyl beta-N-((2-hydroxyphenyl)methylidene)dithiocarbazate, 2) are prepared via ligand-exchange reactions in ethanolic solutions starting from [Re(V)(O)Cl(4)](-) in the presence of PPh(3) or from [Re(V)(O)Cl(3)(PPh(3))(2)]. The distorted octahedral coordination sphere of these compounds is saturated by a chelated hydrazido group, a facially ligated ONS Schiff base, and PPh(3). Reduction-substitution reactions starting from [NH(4)][Re(VII)O(4)] in acidic ethanolic mixtures containing PPh(3) and H(2)L(n) (or its dithiocarbazic acid precursor H(3)L(4)) produce another example of chelated hydrazido(3-) rhenium(V) derivative, namely [Re(eta(2)-L(4))Cl(2)(PPh(3))(2)], 3. On the contrary, the N-methyl-substituted dithiocarbazic acid H(2)L(3) reacts with perrhenate to give the known nitrido complex [Re(N)Cl(2)(PPh(3))(2)]. Rhenium(V) complexes incorporating the robust eta(2)-hydrazido moiety represent key intermediates helpful for the comprehension of the reaction pathway which generates nitridorhenium(V) species starting from oxo precursors. An essential requirement for the stabilization of such chelated hydrazido-Re(V) units is the triple deprotonation at the hydrazine nitrogens, thereby providing efficient pi-electron circulation in the resulting five-membered ring. The thermal stability of these units is affected by the nature of the anchoring donor, thione sulfur ensuring stronger chelation than nitrogen and oxygen. The eta(2)-hydrazido complexes are characterized by conventional physicochemical techniques, including the X-ray crystal structure determination of 1 and 3.     

Chemical reactivity of analogous technetium(V) and rhenium(V) dioxo complexes

All complexes of the series [MO₂L₂]⁺ (M=Tc, Re; L=ethylenediamine (en), 1,3-diaminopropane (1,3-dap)) have been synthesized and their chemical reactivities investigated. The following properties were studied: stability of the aqueous solutions at different pH values, substitution kinetics, lipophilicity and protein binding. The complexes show very similar reactivity in aqueous solution. From a radiopharmaceutical point of view, no significant difference in their in vivo behavior is expected.     

Methyloxorhenium(V) complexes with two bidentate ligands: syntheses and reactivity studies

Four new methyloxorhenium(V) complexes were synthesized: MeReO(PA)(2) (1), MeReO(HQ)(2) (2), MeReO(MQ)(2) (3), and MeReO(diphenylphosphinobenzoate)(2) (4) (in which PAH = 2-picolinic acid, HQH = 8-hydroxyquinoline, and MQH = 8-mercaptoquinoline). Although only one geometric structure has been identified crystallographically for 1, 2, and 3, two isomers of 3 and 4 in solution were detected by NMR spectroscopy. These compounds catalyze the sulfoxidation of thioethers by pyridine N-oxides and sulfoxides. The rate law for the reaction between pyridine N-oxides and thioethers, catalyzed by 1, shows a first-order dependence on the concentrations of pyridine N-oxide and 1. The second-order rate constants of a series of para-substituted pyridine N-oxides fall in the range of 0.27-7.5 L mol(-)(1) s(-)(1). Correlation of these rate constants by the Hammett LFER method gave a large negative reaction constant, rho = -5.2. The next and rapid step does not influence the kinetics, but it could be explored with competition experiments carried out with a pair of methyl aryl sulfides, MeSC(6)H(4)-p-Y. The value of each rate was expressed relative to the reference compound that has Y = H. A Hammett analysis of k(Y)/k(H) gave rho = -1.9. Oxygen-18 labeled 1 was used in a single turnover experiment for 4-picoline N-oxide and dimethyl sulfide. No (18)O-labeled DMSO was found. We suggest that the reaction proceeds by way of two intermediates that were not observed during the reaction. The first intermediate contains an opened PA-chelate ring; this allows the pyridine N-oxide to access the primary coordination sphere of rhenium. The second intermediate is a cis-dioxorhenium(VII) species, which the thioether then attacks. Oxygen-18 experiments were used to show that the two oxygens of this intermediate are not equivalent; only the new oxygen is attacked by, and transferred to, SR(2). Water inhibits the reaction because it hydrolyzes the rhenium(VII) intermediate.     

Calix[4]arene rhenium(V) complexes as potential radiopharmaceuticals

The calix[4]arene platform was used for the syntheses of novel rhenium(V) complexes, that may have potential applications as radiopharmaceuticals. The reaction of ReO(PPh3)2Cl3 with tetradentate N2O2-calix[4]arene ligand 8 in ethanol gave the novel mixed-ligand rhenium complex 9 with the structure ReO(N2O2-calix)OEt. The configuration was elucidated by using a number of 1H NMR techniques. In 9, the ethoxy ligand could be easily and quantitatively exchanged for another monodentate ligand to give complex 12. Tetradentate N2S2-calix[4]arene ligand 15 formed the rhenium complex 16 either via reaction with ReO(PPh3)2Cl3 in an organic solvent or by reaction with rhenium gluconate in an aqueous solution. Complex 16 showed good stability in phosphate-buffered saline solution (37 degrees C, 5 d). The crystal structures of a mono- and a bimetallic complex were determined. The bimetallic N2O2-calixarene complex dimer 11 crystallized in the monoclinic space group C2/c, with a = 38.963(5) A, b = 23.140(6) A, c = 27.382(6) A, beta = 128.456(10) degrees, V = 19,333(7) A3, Z = 8, and final R = 0.0519. The monometallic N2S2 model complex 17 crystallized in the monoclinic space group Cc, with a = 15.715(2) A, b = 12.045(2) A, c = 20.022(3) A, beta = 94.863(12) degrees, V = 3776.3(10) A3, Z = 4, and final R = 0.0342.     

Synthesis and characterization of novel rhenium(V) tetradentate N2O2 Schiff base monomer and dimer complexes

Several rhenium(V) oxo complexes with tetradentate N(2)O(2) Schiff base ligands were synthesized and characterized. The general synthetic procedure involved reaction of [NBu(4)][ReOCl(4)] with a tetradentate Schiff base ligand (L(1) = N,N'-ethylenebis(acetylacetoneimine), (acac(2)en) or L(2) = N,N'-propylenebis(acetylacetoneimine) (acac(2)pn)) in ethanol solution to generate complexes of the form trans-ReOX(L) where X = Cl(-), MeO(-), ReO(4)(-), or H(2)O. The product isolated from the reaction was found to be dependent on the reaction conditions, in particular the presence or absence of water and/or base. The mu-oxo-Re(2)O(3)(L)(2) dimers were synthesized and characterized for chemical and structural comparison to the related monomers. Conversion of the monomer to its dimer analogue was followed qualitatively by spectrophotometry. The complexes were characterized by (1)H and (13)C NMR, UV-vis, and IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. The crystallographic data reported for the structures are as follows: trans-[ReO(OH(2))(acac(2)en)]Cl (H(20)C(12)ClN(2)O(4)Re) 1, triclinic (Ponemacr;), a = 7.2888(6) A, b = 9.8299(8) A, c = 10.8195(9) A, alpha = 81.7670(10) degrees, beta = 77.1510(10) degrees, gamma = 87.6200(10) degrees, V = 747.96(11) A(3), Z = 2; trans-[ReO(OReO(3))(acac(2)en)] (H(18)C(12)N(2)O(7)Re(2)) 2, monoclinic (P2(1)/c), a = 7.5547(4) A, b = 8.7409(5) A, c= 25.7794(13) A, beta = 92.7780(10) degrees, V = 1700.34(16) A(3), Z = 4; trans-[ReOCl(acac(2)pn)] (H(20)C(13)N(2)O(3)ClRe) 3, monoclinic (P2(1)/c), a = 8.1628(5) A, b = 13.0699(8) A, c = 28.3902(17) A, beta = 97.5630(10) degrees, V = 3002.5(3) A(3), Z = 8; trans-[ReO(OMe)(acac(2)pn)] (H(23)C(14)N(2)O(4)Re) 4, monoclinic (P2(1)/c), a = 6.7104(8) A, b = 27.844(3) A, c = 8.2292(9) A, beta = 92.197(2) degrees, V = 1536.4(3) A(3), Z = 4; trans-[mu-oxo-Re(2)O(3)(acac(2)en)(2)] (H(36)C(24)N(4)O(7)Re(2)) 5, monoclinic (P2(1)/n), a = 9.0064(5) A, b = 12.2612(7) A, c = 12.3695(7) A, beta = 90.2853(10) degrees, V = 1365.94(13) A(3), Z = 2; and trans-[mu-oxo Re(2)O(3)(acac(2)pn)(2)] (H(40)C(26)N(4)O(7)Re(2)) 6, monoclinic (P2(1)/n), a = 9.1190(5) A, b = 12.2452(7) A, c = 12.8863(8) A, beta = 92.0510(10) degrees, V = 1438.01(14) A(3), Z = 2.     

Post-protein-binding reactivity and modifications of the fac-[Re(CO)3]+ core

The reactivity of the [Re(CO)(3)(H(2)O)(2)](+) complex coordinated to the His15 residue of HEW lysozyme is described. In the fully metalated protein (Lys-1), the Re ion retains its reactivity only toward selected ligands, while others induce a ligand-mediated demetalation of the enzyme. It is further shown that some of the complexes that may be "engineered" on the lysozyme do not react with the free protein even if present in solution in excess. The formation of stable metal adducts starting from Lys-1 was confirmed by X-ray crystallography.     

New approach to the chemistry of technetium(V) and rhenium(V) phenylimido complexes: novel [M(NPh)PNP]3+ metal fragments (M = Tc, Re; PNP = aminodiphosphine) suitable for the synthesis of stable mixed-ligand compounds

Ligand-exchange reactions of the aminodiphosphine ligand bis[(2-diphenylphosphino)ethyl]amine hydrochloride (PNHP x HCl) with labile M(NPh)Cl3(PPh3)2 precursors (M = Re, Tc) in the presence of triethylamine yield monocationic phenylimido mer,cis-[M(NPh)Cl2(PNHP)]Cl (M = Re, 1; Tc, 2) intermediate complexes. X-ray analyses show that in both compounds the aminodiphosphine acts as a tridentate ligand dictating a mer,cis arrangement. Two chloride ligands, respectively in an equatorial and in the axial position trans to the linear M-NPh moiety, fill the remaining positions in a distorted-octahedral geometry. The chloride trans to the metal-imido core is labile, and is replaced by an alcoholate group, without affecting the original geometry, as established in mer,cis-[Re(NPh)(OEt)Cl(PNHP)]Cl 4. Otherwise, ligand-exchange reactions involving the aminodiphosphine bis[(2-diphenylphosphino)ethyl]methylamine (PNMeP), in which the central secondary amine has been replaced by a tertiary amine function, or its hydrochloride salt (PNMeP x HCl) give rise to three different species, depending on the experimental conditions: fac,cis-[Re(NPh)Cl2(PNMeP)]Cl 3a, cis,fac-Re(NPh)Cl3(PNMeP) x HCl 3b, and mer,trans-[Re(NPh)Cl2(PNMeP)]Cl 3c, which are characterized in solution by multinuclear NMR studies. The monodentate groups incorporated in these intermediate compounds, either halides and/or ethoxide, undergo substitution reactions with bidentate donor ligands such as catechol, ethylene glycol, and 1,2-aminophenol to afford stable mixed ligand complexes of the type [M(NPh)(O,O-cat)(PNP)]Cl [PNP = PNHP M = Re 5, Tc 6; PNP = PNMeP M = Re 7], [Re(NPh)(O,O-gly)(PNP)]Cl [PNP = PNHP 8, PNMeP 9] and [Re(NPh)(O,N-ap)(PNMeP)]Cl 10. X-ray diffraction analyses of the representative compounds 5 and 8 reveal that the aminodiphosphine switches from the meridional to the facial coordination mode placing the heteroatom of the diphosphine trans to the phenylimido unit and the bidentate ligand in the equatorial plane. Solution-state NMR studies suggest an analogous geometry for 6, 7, 9, and 10. Comparison with similar mixed ligand complexes including the terminal nitrido group is discussed.     

Cluster carbonyls of the [Re6(mu3-Se)8]2+ core

The first [Re(6)(mu(3)-Se)(8)](2+) core-containing cluster carbonyls, [Re(6)(mu(3)-Se)(8)(PEt(3))(5)(CO)][SbF(6)](2) and trans-[Re(6)(mu(3)-Se)(8)(PEt(3))4(CO)(2)][SbF(6)](2), were produced by reacting [Re(6)(mu(3)-Se)(8)(PEt(3))(5)I]I and trans-[Re(6)(mu(3)-Se)8(PEt(3))(4)I2], respectively, with AgSbF(6) in CO-saturated dichloromethane solutions. Spectroscopic and crystallographic studies suggest significant cluster-to-CO back-donation in these novel cluster derivatives and interesting electronic structures. Thermal and photolytic studies of the mono-carbonyl complex revealed its interesting and synthetically useful reactivity in producing new cluster derivatives.     

Organoimido complexes of tungsten and rhenium: Oxo-imido and bis-imido complexes of tungsten(VI), and phenylimido complexes of rhenium(VI) and (V). The X-ray crystal structures of [W(NCMe3)(NPh)Cl2(bipy)] and [Re(NPh)Cl3(NH2CMe3)2]

Reaction of Me₃CNH₂ or Me₃SiNHCMe₃ with WOCl₄ gives a mixture containing [W(O)(NCMe₃)Cl₂(NH₂CMe₃)]_x which on further reaction with 2,2′-bipyridyl (bipy) gives [W(NCMe₃)₂Cl₂(bipy)] and insoluble oxo complexes. Reaction of WOCl₄ with p-MeC₆H₄N(SiMe₃)₂ and then bipy gives [W(NC₆H₄Me-p)₂Cl₂(bipy)] and [W(O)(NC₆H₄Me-p)Cl₂(bipy)]; [W(NPh)Cl₄]₂ reacts with p-MeC₆H₄N(SiMe₃)₂ and then bipy to give [W(NPh)(NC₆H₄Me-p)Cl₂(bipy)]. [W(NCMe₃)(μ-NPh)Cl₂(NH₂CMe₃)]₂ and bipy give [W(NCMe₃)(NPh)Cl₂(bipy)] (6). ReOCl₄ reacts with PhNCO to give [Re(NPh)Cl₄]_x which in tetrahydrofuran (THF) or MeCN give the adducts [Re(NPh)Cl₄(THF)] and [Re(NPh)Cl₄(MeCN)]. [Re(NPh)Cl₄]_x reacts with Me₄NCl to give [Me₄N][Re(NPh)Cl₅], with PPh₃ to give [Re(NPh)Cl₃(PPh₃)₂] and with Me₃ SiNHCMe₃ gives [Re(NPh)Cl₃(NH₂CMe₃)₂] (12). The complexes were characterized by elemental analysis, IR, ¹H and ¹³C NMR spectroscopy. The structures of [W(NCMe₃)(NPh)Cl₂(bipy)] (6) and [Re(NPh)Cl₃(NH₂CMe₃)₂] (12) were determined by single-crystal X-ray diffraction methods. Crystals of (6) are orthorhombic, space group P2₁2₁2₁, with a = 8.879(3) Å, b = 13.036(3) Å, c = 18.837(4) Å; crystals of (12) are orthorhombic, space group Pbcn with a = 14.140(1) Å, b = 11.806(1), Å, c = 11.936(3) Å. Both structures were solved by Patterson and Fourier methods and refined to R values of 0.053 for the 2138 observed data for (6) and 0.035 for the 1108 observed data for (12). In complex (6) the tungsten atom is in a distorted octahedral environment comprising cis-t-butylimido and phenylimido groups, trans chlorides and bidentate bipy. The bipy nitrogens lie trans to the imid o functions. Observed distances are: WN_phenylimido 1.774(8) Å, WN_t-butylimido 1.754(10) Å, WCl 2.412(3) and 2.390(3) Å and WN_bipy 2.312(10) Å and 2.333(9) Å. Interaction between the t-butylimido methyl groups and bipy is relieved by lengthening of one WN_bipy bond. In complex (12) the rhenium atom is in a distorted octahedral environment comprising three chloride ligands, two trans-t-butylamine ligands and a phenylimido ligand. Observed distances are: ReN_phenylimido 1.709(11) Å, ReN_t-butylamine 2.187(7) Å, and ReCl 2.404(2) and 2.411(5) Å. The complex attains an 18-electron count without π-bonding from the chloro ligands.     

The reactivity of cationic [trioxo-(1,4,7-triazacyclononane) rhenium(VII)] and oxorhenium(V) complexes containing triazamacrocycles

The reduction of colourless [LRe^VIIO₃]Br in an acetone-water mixture (6: 1) with zinc amalgam affords green, air-sensitive [LRe^VO₂Br] which forms a violet complex [LReO(μ-O)₂ReOBr₂]in aqueous solution (L = 1,4,7-triazacyclononane; C₆H₁₅N₃). From a similar reduction of [LReO₃]ReO₄ the violet neutral complex [LReO(μ-O)₂ReO(ReO₄)₂] was obtained. [LReO₃]⁺ is deprotonated in alkaline solution (pK_a = 10.3 + 0.2, 25°C) and [(C₆H₁₄N₃)ReO₃] was isolated as a yellow solid. The latter amido rhenium(VII) compound reacted in dimethylformamide with R---X (R = CH₃, benzyl; X = Cl), affording at the cyclic amine, N,N′,N″-trisalkylated complexes of the type [L′ReO₃]X. The monomeric rhenium(V) complexes [LReOX₂]X (X = Cl, Br, I) were obtained from the reaction of [n-Butyl₄N]ReOX₄ and L in acetonitrile. IR, UV-vis, ¹⁷O NMR spectra of these compounds are reported.     

Paramagnetic triangular rhenium sulfide cluster [Re3S4(Dppe)3(NCS)3]Br

A new cluster [Re₃S₄(Dppe)₃(NCS)₃]Br (Dppe = Ph₂PCH₂CH₂PPh₂) is synthesized. The molecular and crystal structures of the cluster are determined by X-ray diffraction analysis. The magnetochemical data indicate the high-spin ground state (S = 3/2) of the cluster at room temperature.     

Syntheses and structures of rhenium(IV) and rhenium(V) complexes with ethanedithiolato ligands

A novel dimeric rhenium(IV) complex, [Re2(SCH2CH2S)4], and a monomeric methyloxorhenium(V) complex, [CH3ReO(SCH2CH2S)PPh3], were synthesized from methyloxorhenium(V) complexes and characterized crystallographically. The structure of [Re2(SCH2CH2S)4], the formation reaction of which showed surprising demethylation conceivably through the homolytic cleaveage of the rhenium-carbon bond, features distorted trigonal prismatic coordination of sulfurs around the metal center and a rhenium-rhenium triple bond. A revised structure, [Tc2(SCH2CH2S)4], is proposed for a related technetium complex, originally identified as [Tc2(SCH2CH2S)2(SCH=CHS)2] (Tisato et al. Inorg. Chem. 1993, 32, 2042). Additionally, a new compound, CH3Re(O)(SPh)2PPh3, was prepared.     

Polynuclear vanadium complexes from thermal decomposition of [V3O(O2CPh)6(H2O)3]Cl

Solid-state decomposition of [V3O(O2CPh)6(H2O)3]Cl at 300 degrees C followed by alcoholysis of the product gives the new vanadium complexes [V6O6(PhCO2)6(CH3O)6(CH3OH)3] (1), [V6O6(PhCO2)6(C2H5O)6(C2H5OH)3] (2), [V6O6(PhCO2)6(C3H7O)6(C3H7OH)3] (3), [V6O6(PhCO2)6(C4H9O)6(C4H9OH)3] (4) and [V4O4(OCH3)6(O2CPh)2(HOCH3)2] (5). Complexes 2, 3 and 5 have been crystallographically characterised. DC magnetic susceptibility studies on complex shows antiferromagnetic coupling leading to a S = 0 spin ground state.     

Hexanuclear iron(III) salicylaldoximato complexes presenting the [Fe6(mu3-O)2(mu2-OR)2]12+ core: syntheses, crystal structures, and spectroscopic and magnetic characterization

The use of salicylaldehyde oxime (H2salox) in iron(III) carboxylate chemistry has yielded two new hexanuclear compounds [Fe6(mu3-O)2(O2CPh)10(salox)2(L)2].xMeCN.yH2O [L = MeCONH2, x = 6, y = 0 (1); L = H2O, x = 2, y = 3 (2)]. Compound 1 crystallizes in the triclinic space group P with (at 25 degrees C) a = 13.210(8) A, b = 13.87(1) A, c = 17.04(1) A, alpha = 105.79(2) degrees , beta = 96.72(2) degrees , gamma = 116.69(2) degrees , V = 2578.17(2) A(3), and Z = 1. Compound 2 crystallizes in the monoclinic space group C2/c with (at 25 degrees C) a = 21.81(1) A, b = 17.93(1) A, c = 27.72(1) A, beta = 111.70(2) degrees , V = 10070(10) A(3), and Z = 4. Complexes 1 and 2 contain the [Fe6(mu3-O)2(mu2-OR)2]12+ core and can be considered as two [Fe3(mu3-O)] triangular subunits linked by two mu2-oximato O atoms of the salox2- ligands, which show the less common mu3:eta1:eta2:eta1 coordination mode. The benzoato ligands are coordinated through the usual syn,syn-mu2:eta1:eta1 mode. The terminal MeCONH2 ligand in 1 is the hydrolysis product of the acetonitrile solvent in the presence of the metal ions. M?ssbauer spectra from powdered samples of 2 give rise to two well-resolved doublets with an average isomer shift consistent with that of high-spin Fe(III) ions. The two doublets, at an approximate 1:2 ratio, are characterized by different quadrupole splittings and are assigned to the nonequivalent Fe(III) ions of the cluster. Magnetic measurements of 2 in the 2-300 K temperature range reveal antiferromagnetic interactions between the Fe(III) ions, stabilizing an S = 0 ground state. NMR relaxation data have been used to investigate the energy separation between the low-lying states, and the results are in agreement with the susceptibility data.     

Synthesis and characterization of manganese and rhenium tricarbonyl complexes with (O,O,O)-donor ligands

Complexes of the type [(C₅H₅)Co{P(O)R₂}₃]^?, R = OCH₃, OC₂H₅, react as tridentate oxygen ligands L^? with [MBr(CO)₅], M = Mn, Re, in hexane or tetrahydrofuran to give the tricarbonyl derivatives [LM(CO)₃]. The slightly volatile yellow crystalline compounds have been characterized by elemental analysis, ¹H NMR, IR and mass spectra. The low CO stretching frequencies indicate that the ligands L^? are good π-donor ligands.     

Oxidomolybdenum(VI) complexes with atrane-type [O3N] ligands

Dioxomolybdenum(VI) complex [MoO₂Cl₂(dmso)₂] reacts with a series of tetradentate O₃N-type aminoalcohol–bisphenol ligands to form oxomolybdenum(VI) complexes of type [MoOCl(Lⁿ)]. The reaction of H₃L¹ produces [MoOCl(L¹)] as two separable isomers, whereas the reaction of H₃L² or H₃L³ yields a single product. The X-ray analyses of cis- and trans-[MoOCl(L¹)] reveal that the complexes are formed of monomeric molecules. The ligands have tetradentate coordination through three oxygen donors and one nitrogen donor, which is located trans to the terminal oxo group. The sixth coordination site is occupied by a chloro ligand.     

Characterization and application of the fac-[188Re(CO)3(H2O)3]+ core

Summary Fac-[¹⁸⁸Re(CO)₃(H₂O)₃]⁺ was synthesized with an overall radiochemical yield of 80±5%, and more than 95% radiochemical purity after a QMA Sep-Pak column separation. Fac-[Re(CO)₃(H₂O)₃]⁺ was also synthesized as a reference sample. The structure of the precursor, fac-[¹⁸⁸Re(CO)₃(H₂O)₃]⁺, was confirmed by high performance of liquid chromatography (HPLC). MN-His (magnetic nanoparticles coated with silica and modified with an amino silane coupling agent, N-[3-(trimethyoxysilyl)propyl]-ethylenediamine (SG-Si900) and immobilized with histidine) was labeled with fac-[¹⁸⁸Re(CO)₃(H₂O)₃]⁺ and an initial animal test of MN-His was conducted for a magnetic targeting study.