Rhenium and technetium complexes with diphenyl(2-pyridyl)phosphine

In vitro cytotoxicity of Mn(I) and Ru(II) carbonyls with a diphenyl pyridyl phosphine coligand towards leukaemia

Human acute monocytic leukaemia cells were tested under both dark and light conditions for their susceptibility to Mn(I) and Ru(II) carbonyl complexes with a diphenyl pyridyl phosphine coligand. The Ru(II) complex (IC₅₀ = 7.13 ± 0.8 μM) displayed higher outstanding potency against leukaemia than the Mn(I) analogue (54.58 ± 4.1 μM) in the dark and both complexes were completely harmless to healthy mouse bone marrow cells.

Nitrido Technetium-99 m Core in Radiopharmaceutical Applications: Four Decades of Research

The knowledge on element 43 (Tc) of the periodic table, built over the years through the contributions given by the close relationship between chemistry and nuclear medicine, allowed the development of new and increasingly effective radiopharmaceuticals useful both as perfusion and target specific imaging agents for SPECT (single photon emission tomography). Among the manifold Tc-compounds, Tc(V) nitrido complexes played a relevant role in the search for new technetium-99m radiopharmaceuticals, providing efficient labeling procedures that can be conveniently exploited for the design and synthesis of agents, also incorporating small organic molecules or peptides having defined structural features. With this work, we present an overview of four decades of research on the chemistry and on the nuclear medicine applications of Tc(V) nitrido complexes.

Crystal structures and Hirshfeld surface analysis of [κ2-P,N-{(C6H5)2(C5H5N)P}Re(CO)3Br]·2CHCl3 and the product of its reaction with piperidine, [P-{(C6H5)2(C5H5N)P}(C5H11N)Re(CO)3Br]

The coordination of the ligands with respect to the central atom in the complex bromido-tricarbon-yl[diphen-yl(pyridin-2-yl)phosphane-κ2 N,P]rhenium(I) chloro-form disolvate, [ReBr(C17H14NP)(CO)3]·2CHCl3 or [κ2-P,N-{(C6H5)2(C5H5N)P}Re(CO)3Br]·2CHCl3, (I·2CHCl3), is best described as a distorted octa-hedron with three carbonyls in a facial conformation, a bromide atom, and a biting P,N-di-phenyl-pyridyl-phosphine ligand. Hirshfeld surface analysis shows that C-Cl⋯H inter-actions contribute 26%, the distance of these inter-actions are between 2.895 and 3.213 Å. The reaction between I and piperidine (C5H11N) at 313 K in di-chloro-methane leads to the partial decoord-ination of the pyridyl-phosphine ligand, whose pyridyl group is replaced by a piperidine mol-ecule, and the complex bromido-tricarbon-yl[diphen-yl(pyridin-2-yl)phosphane-κP](piperidine-κN)rhenium(I), [ReBr(C5H11N)(C17H14NP)(CO)3] or [P-{(C6H5)2(C5H5N)P}(C5H11N)Re(CO)3Br] (II). The mol-ecule has an intra-molecular N-H⋯N hydrogen bond between the non-coordinated pyridyl nitro-gen atom and the amine hydrogen atom from piperidine with D⋯A = 2.992 (9) Å. Thermogravimetry shows that I·2CHCl3 losses 28% of its mass in a narrow range between 318 and 333 K, which is completely consistent with two solvating chloro-form mol-ecules very weakly bonded to I. The remaining I is stable at least to 573 K. In contrast, II seems to lose solvent and piperidine (12% of mass) between 427 and 463 K, while the additional 33% loss from this last temperature to 573 K corresponds to the release of 2-pyridyl-phosphine. The contribution to the scattering from highly disordered solvent mol-ecules in II was removed with the SQUEEZE routine [Spek (2015 ▸). Acta Cryst. C71, 9-18] in PLATON. The stated crystal data for M r, μ etc. do not take this solvent into account.

Syntheses and Molecular Structure of Some Rh and Ru Complexes with the Chelating Diphenyl (2-Pyridyl)phosphine Ligand

The rhodium(III) complex mer,cis-[RhCl3(PPh2py-P,N)(PPh2py-P)] (1) (PPh2py = diphenyl (2-pyridyl)phosphine) has been prepared from RhCl3 x 3H2O and PPh2py and converted to the trans,cis-[RhCl2(PPh2py-P,N)2]PF6 (2) in acetone solution by treatment with Ag+ and PF6(-). Ruthenium(III) and ruthenium(II) compounds with PPh2py, mer,cis-[RuCl3(PPh2py-P,N)(PPh2py-P)] (3) and mer-[RuCl(PPh2py-P,N)2(PPh2py-P)]Cl (5) have been obtained from DMSO precursor complexes. In a chloroform solution, complex (5) isomerizes to fac-[RuCl(PPh2py-P,N)2(PPh2py-P)]Cl (fac-5). All compounds have been characterized by MS, UV-vis, IR, and 1H and 31P{1H} NMR spectroscopy, and the Ru(III) compound has been characterized by EPR spectroscopy as well. The crystal structures of 1, 2, 3, and fac-5 have been determined. In all compounds under investigation, at least one pyridylphosphine acts as a chelate ligand. The 31P chemical shifts for chelating PPh2py-P,N depend on the Ru-P bond lengths.

Reactivity of [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (tim(Me) = 2-mercapto-1-methylimidazolyl) toward neutral substrates

The complex [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (2a) (tim(Me) = 2-mercapto-1-methylimidazolyl) reacts with a variety of neutral substrates to afford new complexes featuring the dihydrobis(2-mercapto-1-methylimidazolyl)borate coordinated in a bidentate or unidentate fashion. By treating 2a with unidentate ligands, the mononuclear complexes [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)(L)] (L = imidazole (5), 4-(dimethylamino)pyridine (6), tert-butylisonitrile (7), triphenylphosphine (8)) were formed, upon replacement of the agostic B-H...Re bond by the correspondent unidentate ligand. With potentially bidentate substrates, 2a is transformed into mononuclear or dinuclear complexes, depending on the atom donor set of the reacting substrates. Reaction of compound 2a with ethylenediamine (en) gave the complex [Re[kappa(1)-H(2)B(tim(Me))(2)](CO)(3)(en)] (9), because of cleavage of the agostic interaction, dechelation of one mercaptoimidazolyl ring, and bidentate coordination of the amine. By contrast, 1,2-bis(diphenyl)phosphinoethane (dppe) is not able to replace the mercaptoimidazolyl ring, and the dimer [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)](2)(mu-dppe) (10) was formed. The novel Re(I) tricarbonyl complexes (5-10) have been fully characterized, including by X-ray diffraction analysis in the case of 6, 8, 9, and 10. The X-ray diffraction study confirmed the unprecedented unidentate coordination mode of the dihydrobis(2-mercapto-1-methylimidazolyl)borate in complex 9.