Abstract:A series of neutral rhenium(V) oxo complexes was synthesized by the reaction of ReOBr4-with diamino-thiolthioether ligands of the type (RSC(CH~)~CH~NH(O-C&)NHCH~C(CH~)~SH. The complexes were characterized by IR, UVIvisible, and 'H and 13C NMR spectroscopy and by fast-atom-bombardment mass spectroscopy. The single-crystal X-ray structure determination on two of the complexes, where R = CH2CH-CH2 and CH2CH2-CH3, showed them to consist of a square pyramidal ReVON2S2 core. R~O[CH~=CHCHZSC(CH~)~CH~N(~-C6&)NCH2C(CH3… Show more
“…The ReO1(terminal oxo) has a distance of 1.683(3) Å, while the Re−O2 distance of 2.184(3) Å represents a lengthened single-bond distance, demonstrating the trans influence of the terminal oxo ligand. The Re−S bond lengths of 2.301(1) and 2.377(1) Å are within the range observed for Re(V)−sulfur coordinated complexes. − 2 The structure of 3 , showing the atom-labeling scheme and 50% thermal ellipsoids.…”
“…The ReO1(terminal oxo) has a distance of 1.683(3) Å, while the Re−O2 distance of 2.184(3) Å represents a lengthened single-bond distance, demonstrating the trans influence of the terminal oxo ligand. The Re−S bond lengths of 2.301(1) and 2.377(1) Å are within the range observed for Re(V)−sulfur coordinated complexes. − 2 The structure of 3 , showing the atom-labeling scheme and 50% thermal ellipsoids.…”
“…In typical, stable oxorhenium(V) and oxotechnetium(V) complexes, there are often two nitrogen and two sulfur donor atoms; however, most known complexes involve a diamine dithiol (DADT) or similar coordination motif. Though thioether donors are found in stable oxorhenium(V) systems, they have not been extensively investigated. However, there have been some studies of the diamide thioether thiol (DATT) motif, , which has shown interesting properties, such as low binding to blood plasma protein .…”
We are developing oxometal(V) complexes as high affinity ligands
for the estrogen receptor. When
labeled with technetium-99m, these complexes might be used as imaging
agents for estrogen
receptor-positive breast tumors. We describe the synthesis of a
tetradentate oxorhenium(V) amino
amido thioether thiol (AATT) complex in which the metal complex
replaces the CD ring portion of
estradiol. This complex is a close steric congener of the steroid
and has a similar molecular volume.
It was synthesized from norphenylephrine via an efficient
Pictet−Spengler cyclization to give a
tetrahydroisoquinoline that was then readily elaborated into the
tetradentate chelate system.
Treatment with an oxorhenium(V) salt led to the formation of the
desired complex as a mixture of
two diastereomers in modest yield. The relative stereochemistry of
these isomers was easily
assigned from their NMR spectra. On the basis of their
octanol−water partition coefficients, these
complexes are considerably more hydrophilic than is estradiol, and
their binding affinity for the
estrogen receptor is low. The AATT unit in these complexes
represents a new chelation system for
the oxometal(V) complexes of group 7 transition metals, and compared to
other closely related bis-bidentate and other tetradentate systems we have studied, these
complexes are quite stable.
Nevertheless, the low binding affinity of these complexes for the
estrogen receptor emphasizes the
fact that metal complexes must most likely have an electronic
complementarity with good receptor
ligands, as well as a size and shape complementarity, in order for them
to exhibit high affinity
receptor binding.
“…In complexes 3a,b and 4a,b the loss of aromatic amine nitrogen hydrogens, which is unusual in amines, may be attributed to the greater acidity imparted to the aniline-like amine hydrogens by conjugation with the aromatic ring. 16 Moreover, only a unique signal for hydrogen (3a,b) and the methyl group (4a,b) of the aromatic nitrogen, respectively, was detected indicating sp 2 hybridization for the aromatic amine nitrogen. Methylene protons of the tetradentate ligand framework were found to be diastereotopic (AB pattern) with coupling constants in the range 17-19 Hz.…”
Section: Preparation Of Rhenium(v) Complexesmentioning
Twelve novel oxo-technetium and oxo-rhenium complexes based on N2S2-, N2SO- or N3S-tetradentate semi-rigid ligands have been synthesised and studied herein. By reacting the ligands with a slight excess of suitable [MO]3+ precursor (ReOCl3(PPh3)2 or [NBu4][99gTcOCl4]), the monoanionic complexes of general formula [MO(Ph-XN2S)]- could be easily produced in high yield. The complexes have been characterized by means of IR, electrospray mass spectrometry, elemental analysis, NMR and conductimetry. The crystal structures of [PPh4][ReO(Ph-ON2S)] 1b and [NBu4][99gTcO(Ph-ON2S)] 1c have been established. The [MO]3+ moiety was coordinated via the two deprotonated amide nitrogens, the oxygen and the terminal sulfur atoms in 1b and 1c. In both compounds, the ON2S coordination set is in the equatorial plane, and the complexes adopted a distorted square-pyramidal geometry with an axial oxo-group. The chemical and structural identity of the different prototypic complexes (rhenium, 99gTc complexes and their corresponding 99mTc radiocomplexes) have been also established by a comparative HPLC study.
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