ic7b00894_si_001.pdf (4.78 MB)
Rhenium(I) Tricarbonyl Complexes with (2-Hydroxyphenyl)diphenylphosphine as PO Bidentate Ligand
journal contribution
posted on 2017-06-28, 13:49 authored by Antonio Shegani, Charalampos Triantis, Berthold A. Nock, Theodosia Maina, Christos Kiritsis, Vassilis Psycharis, Catherine Raptopoulou, Ioannis Pirmettis, Francesco Tisato, Minas S. PapadopoulosIn the present work,
we investigated potential means to obtain neutral tricarbonyl mixed-ligand fac-[M(CO)3L1L2] complexes
(M = Re, 99mTc) containing the (2-hydroxyphenyl)diphenylphosphine
(POH) bidentate ligand (L1H) and a series of monodentate
ligands (L2). First, fac-[Re(CO)3(PO)(H2O)], 1, was synthesized by reaction
of POH and [Et4N]2[Re(CO)3Br3] in equimolar amounts in MeOH at room temperature. Interestingly,
with excess of POH this reaction afforded fac-[Re(CO)3(PO)(POH)], 2, with POH operating both as a bidentate
and as a monodentate ligand. Owing to the presence of the labile aqua
ligand, which can be readily replaced by various monodentate ligands, 1 was further used as a precursor to generate a small library
of the desired fac-[M(CO)3L1L2] complexes. Specifically, by reaction of triphenylphosphine
(PPh3), imidazole (im), pyridine (py), cyclohexyl isocyanide
(cisc), and tert-butyl isocyanide (tbi), the following
products were readily obtained in excellent yields (92%–95%): fac-[Re(CO)3(PO)(PPh3)], 3, fac-[Re(CO)3(PO)(im)], 4, fac-[Re(CO)3(PO)(py)], 5, fac-[Re(CO)3(PO)(cisc)], 6, and fac-[Re(CO)3(PO)(tbi)], 7. All compounds were fully characterized by elemental analysis, IR
and NMR spectroscopies, and electrospray ionization(+) mass spectrometry.
Their solid-state structure was elucidated by X-ray crystallography.
Of considerable interest is the fact that the corresponding 2′–7′ were easily accessible
at the 99mTc-tracer level in quantitative yields after
reaction of POH and the respective monodentate ligand L2 with fac-[99mTc(CO)3(H2O)3]+ in aqueous MeOH, as verified by
comparative chromatographic methods adopting dual photo- and radiometric
detection modes. The high stability displayed by all 99mTc complexes during histidine and cysteine challenge assays underscored
the suitability of the fac-[M(CO)3(PO)L2] system for radiopharmaceutical development purposes.
