[M(CO) 2 (NO)] 2+ , a new core in bioorganometallic chemistry: model complexes of [Re(CO) 2 (NO)] 2+ and [ 99m Tc(CO) 2 (NO)] 2+

Ligand exchange and complex formation kinetics studied by NMR exemplified on fac-[(CO)3M(H2O)]+ (M=Mn, Tc, Re)

“…26 3 ] + (pK a = 7.5) [47]. The value calculated from the acidity dependence of k obs is lower than the pK a calculated from the acidity of a 1 mM solution of the complex (pK a = 2.96) [69].…”

“…Besides the tricarbonyl precursors fac-[(CO) 3 M(H 2 O) 3 ] + another interesting class of molecules can be obtained by replacing one CO ligand by NO + [68][69][70][71]. Compared to the Table 4 Thermodynamic and kinetic parameters for water substitution on fac-[(CO) 3 Fig.…”

3,3-Bis(3,5-dimethylpyrazol-1-yl)propionic acid: A tripodal N,N,O ligand for manganese and rhenium complexes – Syntheses and structures

“…This is due to the trans influence of the two pyrazolyl p-acceptor groups onto the trans metalcarbonyl bonds. Since in 3 and 4 the ''carboxylate arm" is involved in the formation of a 7-ring instead of a 6-ring as in fac- (Table 3) [NO] + is a stronger p-acceptor than CO and changes the charge of the complex by +1, thus creating a ''harder" metal centre as compared to fac-[M(CO) 3 ] + , which is commonly considered as ''soft" [8]. Furthermore, due to its higher charge fac-[M(CO) 2 (NO)] 2+ is assumed to possess a higher binding affinity to anionic chelating ligands that are frequently used as linkers between the metal core and biomolecules [16,17].…”

“…As a third argument for the synthesis of these complexes may serve their possible use in the search for new rhenium and technetium radiopharmaceutics. Besides the fac-[M(CO) 3 ] + -core (M = Re, Tc) the metal fragments [M(CO) 2 (NO)] 2+ and [MO 3 ] + (M = Re, Tc) are subjects of current radiopharmaceutics research [6,8]. 3,3-Bis(3,5-dimethylpyrazol-1-yl)propionato complexes with these fragments will be discussed, as well.…”

Exploring the nitrosyl-approach: “Re(CO)2(NO)”- and “Tc(CO)2(NO)”-complexes provide new pathways for bioorganometallic chemistry

“…The introduction of a charged NO + group instead of a neutral CO group changes the charge of the formed dicarbonyl-nitrosyl complexes by +1 as compared to the original tricarbonyl compounds, while the fac-geometry of the three groups (CO, CO, NO) in the complex is retained. Also the electronic properties of the M(CO) 2 (NO)-complexes differ, as NO + is a stronger p-acceptor, but a weaker r-donor as compared to the isoelectronic CO [6].…”