title: Technetium and rhenium in five-coordinate symmetrical and dissymmetrical nitrido complexes with alkyl phosphino-thiol ligands. Synthesis and structural characterization.
abstract: The reactivity of bulky alkylphosphino-thiol ligands (PSH) toward nitride-M(V, VI) (M = Tc/Re) precursors was investigated. Neutral five-coordinate monosubstituted complexes of the type [M(N)(PS)Cl(PPh(3))] (Tc1-4, Re1-2) were prepared in moderate to high yields. It was found that these [M(N)(PS)Cl(PPh(3))] species underwent ligand-exchange reactions under mild conditions when reacted with bidentate mononegative ligands having soft donor atoms such as dithiocarbamates (NaL(n)) to afford stable dissymmetrical mixed-substituted complexes of the type [M(N)(PS)(L(n))] (Tc5,8-10, Re5-9) containing two different bidentate chelating ligands bound to the [M[triple bond]N](2+) moiety. In these reactions, the dithiocarbamate replaced the two labile monodentate ligands (Cl and PPh(3)) leaving the [M(N)(PS)](+) building block intact. In the above reactions, technetium and rhenium were found to behave in a similar way. Instead, under more drastic conditions, reactions of PSH with [M(N)Cl(2)(PPh(3))(2)] gave a mixture of monosubstituted [M(N)(PS)Cl(PPh(3))] and bis-substituted species [M(N)(PS)(2)] (Tc11-14) in the case of technetium, whereas only monosubstituted [M(N)(PS)Cl(PPh(3))] complexes were recovered for rhenium. All isolated products were characterized by elemental analysis, IR and multinuclear ((1)H, (13)C, and (31)P) NMR spectroscopies, ESI MS spectrometry, and X-ray crystal structure determination of the representative monosubstituted [Tc(N)(PStbu)Cl(PPh(3))] (Tc4) and mixed-substituted [Re(N)(PScy)(L(3))] (Re7) and [Re(N)(PSiso)(L(4))] (Re9) complexes. The latter rhenium complexes represent the first example of a square-pyramidal nitrido Re species with the basal plane defined by a PS(3) donor set. Monosubstituted [M(N)(PS)Cl(PPh(3))] species bearing the substitution-inert [M(N)(PS)](+) moieties act as suitable building blocks proposed for the construction of new classes of dissymmetrical nitrido compounds with potential application in the development of essential and target specific (99m)Tc and (188)Re radiopharmaceuticals for imaging and therapy, respectively.
authors.affiliation: ICIS-CNR, Corso Stati Uniti, 4, 35127 Padova, Italy. bolzati@icis.cnr.it
authors.forename: Cristina
authors.initials: C
authors.lastname: Bolzati
authors.forename: Mario
authors.initials: M
authors.lastname: Cavazza-Ceccato
authors.forename: Stefania
authors.initials: S
authors.lastname: Agostini
authors.forename: Francesco
authors.initials: F
authors.lastname: Tisato
authors.forename: Giuliano
authors.initials: G
authors.lastname: Bandoli
mesh_terms: D001921:Brain / Q000000981:diagnostic imaging; D018360:Crystallography, X-Ray / Q000379:methods; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008968:Molecular Conformation; D010720:Phosphines / Q000138:chemical synthesis* / Q000737:chemistry*; D049268:Positron-Emission Tomography / Q000379:methods; D011859:Radiography; D019275:Radiopharmaceuticals / Q000737:chemistry; D012211:Rhenium / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D013667:Technetium / Q000737:chemistry*; D013859:Thiocarbamates / Q000737:chemistry; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
chemical_list: D008024:Ligands; D010720:Phosphines; D019275:Radiopharmaceuticals; D013438:Sulfhydryl Compounds; D013859:Thiocarbamates; D012211:Rhenium; D013667:Technetium