Reactivity of the [M(PS)₂]⁺ Building Block (M = Re^III and ^99mTc^III; PS = Phosphinothiolate) toward Isopropylxanthate and Pyridine-2-thiolate

The coordination properties of isopropylxanthate (<i>i</i>-Pr-Tiox) and pyridine-2-thiolate (PyS) toward the [M­(PS)₂]⁺ moiety (M = Re and ^99mTc; PS = phosphinothiolate) were investigated. Synthesis and full characterization of [Re­(PS2)₂(<i>i</i>-Pr-Tiox)] (<b>Re1</b>), [Re­(PSiso)₂(<i>i</i>-Pr-Tiox)] (<b>Re2</b>), [Re­(PS2)₂(PyS)] (<b>Re3</b>), and [Re­(PSiso)₂(PyS)] (<b>Re4</b>), where PS2 = 2-(di­phenyl­phosphino)­ethane­thiolate and PSiso = 2-(di­isopropyl­phosphino)­ethane­thiolate, and the structural X-ray analysis of complex <b>Re3</b> were carried out. ^99mTc analogues of complexes <b>Re2</b> (^<b>99m</b><b>Tc2</b>) and <b>Re4</b> (^<b>99m</b><b>Tc4</b>) were obtained in high radiochemical yield following a simple one-pot procedure. The chemical identity of the radiolabeled compounds was confirmed by chromatographic comparison with the corresponding rhenium complexes and by dual radio/UV HPLC analysis combined with ESI­(+)-MS of ^99g/99mTc complexes prepared in carrier-added conditions. The two radiolabeled complexes were stable with regard to trans chelation with cysteine, glutathione, and ethylene­diamino­tetra­acetic acid and in rat and human sera. This study highlights the substitution-inert metal-fragment behavior of the [M­(PS)₂]⁺ framework, which reacts with suitable bidentate coligands to form stable hexacoordinated asymmetrical complexes. This feature makes it a promising platform on which to develop a new class of Re/Tc complexes that are potentially useful in radiopharmaceutical applications

Reactivity of the [M(PS)₂]⁺ Building Block (M = Re^III and ^99mTc^III; PS = Phosphinothiolate) toward Isopropylxanthate and Pyridine-2-thiolate

The coordination properties of isopropylxanthate (<i>i</i>-Pr-Tiox) and pyridine-2-thiolate (PyS) toward the [M­(PS)₂]⁺ moiety (M = Re and ^99mTc; PS = phosphinothiolate) were investigated. Synthesis and full characterization of [Re­(PS2)₂(<i>i</i>-Pr-Tiox)] (<b>Re1</b>), [Re­(PSiso)₂(<i>i</i>-Pr-Tiox)] (<b>Re2</b>), [Re­(PS2)₂(PyS)] (<b>Re3</b>), and [Re­(PSiso)₂(PyS)] (<b>Re4</b>), where PS2 = 2-(di­phenyl­phosphino)­ethane­thiolate and PSiso = 2-(di­isopropyl­phosphino)­ethane­thiolate, and the structural X-ray analysis of complex <b>Re3</b> were carried out. ^99mTc analogues of complexes <b>Re2</b> (^<b>99m</b><b>Tc2</b>) and <b>Re4</b> (^<b>99m</b><b>Tc4</b>) were obtained in high radiochemical yield following a simple one-pot procedure. The chemical identity of the radiolabeled compounds was confirmed by chromatographic comparison with the corresponding rhenium complexes and by dual radio/UV HPLC analysis combined with ESI­(+)-MS of ^99g/99mTc complexes prepared in carrier-added conditions. The two radiolabeled complexes were stable with regard to trans chelation with cysteine, glutathione, and ethylene­diamino­tetra­acetic acid and in rat and human sera. This study highlights the substitution-inert metal-fragment behavior of the [M­(PS)₂]⁺ framework, which reacts with suitable bidentate coligands to form stable hexacoordinated asymmetrical complexes. This feature makes it a promising platform on which to develop a new class of Re/Tc complexes that are potentially useful in radiopharmaceutical applications

Uncommon Anionic Dioxorhenium(V) and Neutral Monooxorhenium(V) Mixed-Ligand Complexes Containing Heterofunctionalized Phosphine Ligands: Syntheses and Structural Characterization

The potentially bidentate hybrid ligand (o-hydroxyphenyl)diphenylphosphine, abbreviated POH, reacted via ligand-exchange with pentavalent rhenium precursors to give a series of six-coordinate mono- and dioxo complexes. Accurate control of the metal:ligand stoichiometric ratio allowed for the isolation of the mono-substituted [ReOCl3(PO)]- (1) and [ReOCl2(PO)(PPh3)] (2) derivatives. 1 was found to be the key intermediate for the syntheses of three more types of bis-substituted compounds:  anionic dioxo [ReO2(PO)2][A] (A = NBu4 (3), AsPh4 (4)), neutral monooxo [ReOX(PO)2] (X = Cl (5), Br (6), I (7)), and neutral monooxo mixed-ligand [ReOX(PO)(PNH)] [PNH = (o-amidophenyl)diphenylphosphine; X = Cl (8), Br (9), I (10)] complexes. In the mono-substituted complexes, the P,O-donors of the bidentate ligand spanned an equatorial (P) and the apical position (O) trans to the ReO linkage in a distorted octahedral arrangement. In all of the bis-substituted monooxo compounds, the second chelate ligated on the equatorial plane almost orthogonally positioned with respect to the first one, the two phosphorus donors showing a mutual cis-(P,P) orientation. Dioxo complexes retained the cis-(P,P) configuration with the bidentate ligands symmetrically coordinated on the equatorial plane normal to the trans-ReO2 core. All the complexes were characterized by various physical techniques, including IR, MS, and 1H/31P{1H} NMR. The X-ray structure of a representative compound for each category, namely [ReOCl3(PO)][NBu4] (1), [ReO2(PO)2][AsPh4] (4), [ReOCl(PO)2] (5), and [ReOCl(PO)(PNH)] (8), were determined. Crystals of 1 were monoclinic, P21/n, a = 10.840(3) Å, b = 22.167(6) Å, c = 15.210(4) Å, β = 95.91(2)°, and Z = 4; those of 4 were triclinic, P1̄, a = 12.679(7) Å, b = 13.082(7) Å, c = 19.649(8) Å, α = 82.64(4)°, β = 81.16(4)°, γ = 62.27(3)°, and Z = 2; those of 5 were orthorhombic, a = 10.225(4) Å, b = 14.208(6) Å, c = 21.771(9) Å, P212121, and Z = 4; and those of 8 were orthorhombic, a = 10.199(2) Å, b = 14.147(4) Å, c = 21.772(6) Å, P212121, and Z = 4. The four structures were solved by the Patterson method and refined by full-matrix least-squares procedures to R = 0.050, 0.063, 0.043, and 0.039 for 1, 4, 5 and 8, respectively. Both solution state (31P{1H} NMR) and solid state (X-ray) demonstrated a cis-(P,P) arrangement for each bis-substituted complex, with the Re atom at the center of a highly distorted octahedron. Detailed analyses of the IR spectra of this series of Re(V) compounds in the region 900−580 cm-1 allowed us the possibility to distinguish between symmetrical and asymmetrical bis-substituted complexes

Synthesis, Characterization, and Crystal Structure of the Water Soluble Copper(I) Complex with Trisulfonated Triphenylphosphine

Synthesis, Characterization, and Crystal Structure of the Water Soluble Copper(I) Complex with Trisulfonated Triphenylphosphin

Synthesis and Characterization of the First Mononuclear Ni^II Phosphorane Imino Complex

Synthesis and Characterization of the First Mononuclear NiII Phosphorane Imino Comple

Synthesis and Characterization of the First Mononuclear Ni^II Phosphorane Imino Complex

Synthesis and Characterization of the First Mononuclear NiII Phosphorane Imino Comple

Novel [^99mTc^III(PS)₂(Ln)] Mixed-Ligand Compounds (PS = Phosphino-thiolate; L = Dithiocarbamate) Useful in Design and Development of Tc^III-Based Agents: Synthesis, in Vitro, and ex Vivo Biodistribution Studies

A general procedure for the preparation of a new class of neutral six-coordinated mixed ligand [^99mTc^III(PS)₂(Ln)] compounds (PS = trisalkyl-phosphino-thiolate; Ln = dithiocarbamate) is reported as well as their in vitro stability and the ex vivo tissue distribution studies. [^99mTc­(PS)₂(Ln)] complexes were prepared in high yield in nearly physiologic conditions following a one-pot procedure. For instance, the chemical identity of [^99mTc­(PSiso)₂(L1)] (PSiso = 2-(diisopropylphosphino)­ethanethiol; L1 = pyrrolidine dithiocarbamate) was determined by HPLC comparison with the corresponding ^99gTc-complex. All complexes comprise the stable [^99mTc^III(PS)₂]⁺ moiety, where the remaining two coordination positions are saturated by a dithiocarbamate chelate, also carrying bioactive molecules (e.g., 2-methoxyphenylpiperazine). [^99mTc­(PS)₂(Ln)] complexes were inert toward ligand exchange reactions. No significant in vitro and in vivo biotransformation were observed, underlining their remarkable thermodynamic stability and kinetic inertness. These results could be conveniently utilized to devise a novel class of ^99mTc^III-based compounds useful in radiopharmaceutical applications

Synthesis and Characterization of the “Sulfur-Rich” Bis(perthiobenzoato)(dithiobenzoato)technetium(III) Heterocomplex

Synthesis and Characterization of the “Sulfur-Rich” Bis(perthiobenzoato)(dithiobenzoato)technetium(III) Heterocomple

Synthesis and Characterization of Novel Trigonal Bipyramidal Technetium(III) Mixed-Ligand Complexes with SES/S/P Coordination (E = O, N(CH₃), S)

Five-coordinate oxotechnetium(V) mixed-ligand complexes [TcO(SES)(S-p-C6H4-OMe)], where SES is a tridentate dithiolato fragment of the type -S(CH2)2E(CH2)2S- (E = O, 1; E = S, 2; E = NMe, 3) are converted via reduction−substitution reactions in the presence of PMe2Ph into the corresponding five-coordinate Tc(III) complexes [Tc(SES)(S-p-C6H4-OMe)(PMe2Ph)] (E = O, 4; E = S, 5; E = NMe, 6). Rearrangement of the original square pyramidal “3 + 1” oxo species to the trigonal bipyramidal “3 + 1 + 1” Tc(III) complexes occurs by placing the three thiolate donors on the basal plane, the phosphine phosphorus, and the heteroatom of the tridentate ligand at the apexes of the bipyramid. These Tc(III) complexes are diamagnetic species, thereby allowing multinuclear NMR characterization in solution, which confirm their structures to be identical to those observed in the solid state via X-ray determinations

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·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·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)·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