Biomedically relevant coordination chemistry of rhenium and the lanthanides

[ReO(ppme)X] (where ppme2− is 2,5-diazo-N,N ′-dimethylhexyl-1,6-bis(phenylphosphinate), X = Br_0.3Cl _0.7) has been synthesized via a substitution reaction and structurally characterized. [ReO(ppme)Cl] has been prepared by a reduction/complexation reaction from [NH₄][ReO₄]. [ReO(ppme)Cl] reacts with thiocyanate and benzene thiolate forming [ReO(ppme)X] (X = − NCS, −SC₆H₅), but the one-pot synthesis of the respective ternary thiolate complexes from perrhenate was not successful. The reduction/complexation reaction of p-methoxybenzenethiol, H₂ppmeCl₄, and perrhenate resulted in the formation of [H₃ppme][ReO(SR)₄], the reaction of which with ReO(ppme)Cl does not lead to [ReO(ppme)SR] in high yields.; The oxorhenium(V) complexes with H₂pmen (N,N′ -bis(2-pyridylmethyl)ethylenediamine, an N₄ ligand) and H₂bped (N,N′-bis(2-pyridylmethyl)ethylenediamine-N,N ′-diacetic acid, an N₄O₂ ligand) have been synthesized and structurally characterized. Along with [ReO(bbpen)] + (where H₂bbpen is N,N′-bis(2-hydroxybenzyl)-N,N ′-bis(2-methylpyridyl)ethylenediamine, an N₄O ₂ ligand) and [ReO(qtp)(OCH₃)₂]+ (where qtp, 2,2′-6′,2″ -6″,2″′-quaterpyridine, has an N₄ donor set), [ReO(H₂pmen)Cl₂] + and [ReO(bped)]+ complexes share a rare seven-coordinate structure with a distorted pentagonal bipyramidal geometry, which represents a potentially general structural motif in ReV = O complexes. The complexes retained their structure in solution.; Chemistry of Re complexes with H₂pmen ligand has been further investigated. Complex cations [ReO(H₂pmen)Cl₂] +, [ReO(HPMen)Cl]+ and [ReO₂(H₂pmen)] + are related by hydrolysis/HCl substitution. (ReO(Hpmen)Cl] + was structurally characterized and found to contain a water-stable amido-Re bond. Dehydrogenation of the N-donor ligand from amine to imine with concomitant two-electron reduction of the Re center occurs readily in these systems. With suitable co-ligands such as 3-hydroxy-4-pyrones, ternary complexes [ReCl(L)(C₁₄H₁₄N₄)][ReO₄], (where C₁₄H₁₄N₄ = H₂pmen-4H and L = 3-hydroxy-4-pyronate anions) can be made from [NH₄][ReO₄], H₂pmen·4HCl and pyrones in one-pot syntheses. These complexes may prove useful in nuclear medicine.; H₅XT (bis{lcub}[bis(carboxymethyl)amino]methyl{rcub}phosphinic acid) is an EDTA4−-like ligand containing an extra phosphinate group. [CoII(XT)]3−, [CoIII(XT)] 2− and a series of [Ln(XT)]2−, complexes have been prepared. The phosphinate group is not coordinated in the Co complexes but is bound in the lanthanide complexes. Solid state and solution behaviours of Ln-XT species are consistent: both mono-protonated and non-protonated species have been found. Protonation of the metal complex does not lead to dissociation of a carboxylate, rather, the proton distributes around the molecular ion. The pM values of Ln-XT are comparable to those of Ln-EDTA but are higher than those of Ln-TMDTA. The inclusion of a phosphinate eases the selectivity of an EDTA-type ligand to late lanthanides.