Synthesis and Characterization of Novel “3 + 2” Oxorhenium Complexes, ReO[SNO][NN]

Abstract

The present paper deals with the synthesis and structural characterization of novel neutral oxorhenium(V) complexes of the general formula ReO[SNO][NN]. The simultaneous action of the tridentate SNO ligand, N-(2-mercaptoacetyl)glycine (1), and the bidentate NN ligand, N-phenylpyridine-2-aldimine (2), on ReOCl3(PPh3)2 leads to the formation of two isomers 4a and 4b of the general formula ReO[SNO][NN], as a result of the different orientations of the NN ligand. In both cases, the SNO donor atoms of the tridentate ligand occupy the three positions in the equatorial plane of the distorted octahedron, whereas the oxo group is always directed toward one of the apical positions. In the first isomer, 4a, the imino nitrogen of the NN ligand occupies the fourth equatorial position and the pyridine type nitrogen is directed trans to the oxo group, while in the second isomer, 4b, the imino nitrogen of the NN ligand occupies the apical position trans to the oxo group and the pyridine type nitrogen completes the equatorial plane of the distorted octahedron. The [SNO][NN] mixed-ligand system was applied in the synthesis of the oxorhenium complex 5 in which the 1-(2-methoxyphenyl)piperazine moiety, a fragment of the true 5-HT1A antagonist WAY 100635, has been incorporated in the NN bidentate ligand (NN is N-{3-[4-(2-methoxyphenyl)piperazin-1-yl]propyl}pyridine-2-aldimine). In this case, high-performance liquid chromatography and NMR showed the existence of one isomer, 5, in which the pyridine nitrogen is trans to the oxo core, as demonstrated by crystal structure analysis.

N-Centered Tripodal Phosphine Re(V) and Tc(V) Oxo Complexes: Revisiting a [3 + 2] Mixed-Ligand Approach

“…85 , 86 Papadopoulos and co-workers have used imino-pyridines as bidentate ligands to form complexes with an [S,N,O]/[N,N] donor set. 62 Pyrazole-derived [N,N,O] ligands have been shown to stabilize [3 + 2] complexes with catechol and ethylene glycol, 63 while [3 + 2] complexes of the closely related pyridyl-derived [N,N,O] ligand published by Abrahams et al have been stabilized using an oxalic acid ligand. 87 The trio of catechol, ethylene glycol, and oxalic acid has been used effectively with a number of different tridentate ligands and were selected as the starting point for exploring further ligand substitution chemistry with 4 .…”

“…Conversely, for {M V O} 3+ cores, “hard” oxygen donors such as catechols, 1,2-diols, and 1,2-dicarboxylic acids are often preferred . In the case of the tridentate scorpionates dithiolates have been used to form [3 + 2] complexes with the [Re V O] 3+ core. , These ligands have been shown to be compatible with β-diketones and diamines, although with only bidentate coordination of the scorpionate exhibited in these latter cases. , Papadopoulos and co-workers have used imino-pyridines as bidentate ligands to form complexes with an [S,N,O]/[N,N] donor set . Pyrazole-derived [N,N,O] ligands have been shown to stabilize [3 + 2] complexes with catechol and ethylene glycol, while [3 + 2] complexes of the closely related pyridyl-derived [N,N,O] ligand published by Abrahams et al have been stabilized using an oxalic acid ligand .…”

“…However, these sets have seen only limited success in, or indeed attempted translation to, 99m Tc radiopharmaceutical formulation. Notable examples with Re include the use of tridentate ligands derived from Schiff bases, diolates and dithiolates; − N-heterocycles; , and heteroscorpionates, but very few have used heterofunctionalized phosphines incorporated into tridentate ligands (Chart c). , More recently, Abram and co-workers have published a series of {M V O} 3+ complexes incorporating tridentate thiosemicarbazones and bidentate benzoylthioureas, which present a promising [3 + 2] strategy for use with technetium (Chart d). , …”

Μελέτη Συμπλόκων Ρηνίου Ως Νέων Αντικαρκινικών Παραγόντων

“…Φασματοσκοπία ΙR. Τα IR φάσματα όλων των συμπλόκων εμφανίζουν χαρακτηριστικές κορυφές στα 950-959 cm -1 οι οποίες είναι ενδεικτικές της δόνησης του δεσμού Re=O 119. Ενδεικτικά παρουσιάζεται το φάσμα ΙR του ReΟ(CH3-SNO)(dppn) στο Σχήμα 9.3.…”