title: Toward organometallic (99m)Tc imaging agents: synthesis of water-stable (99)Tc-NHC complexes.
abstract: (99)Tc(V)O2-NHC complexes containing monodentate and bidentate N-heterocyclic carbenes (NHCs) have been prepared by the reactions of [TcO(glyc)2](-) (glyc = ethyleneglycolato) with 1,3-dimethylimidazoline-2-ylidene (L1), 1,1'-methylene-3,3'-dimethyl-4,4'-diimidazoline-2,2'-diylidene (L2), and 1,1'-methylene-3,3'-diethyl-4,4'-diimidazoline-2,2'-diylidene (L3) in THF. The resulting complexes were fully characterized and their stabilities investigated. While complexes with monodentate NHCs only are hydrolytically unstable, complexes containing bidentate NHCs are water-stable over a broad pH range. The high water stability allows interconversion of the {(99)Tc(V)O2}(+) core into {(99)Tc(V)OCl}(2+) with HCl as the H(+) and Cl(-) source. An alternative procedure to obtain (99)Tc(V)O2-NHC complexes is the in situ deprotonation of imidazolium salts, enabling the preparation of (99)Tc(V)O2-NHC compounds without free NHCs, thus increasing the scope of NHC ligands drastically. The remarkable stability and pH-controllable reactivity of the new complexes underlines the potential of NHCs as stabilizing ligands for (99)Tc complexes and paves the way for the first (99m)Tc-NHC complexes in the future.
authors.affiliation: Institute of Inorganic Chemistry, University of Zurich , Winterthurerstrasse 190, 8057 Zurich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Benz
authors.forename: Bernhard
authors.initials: B
authors.lastname: Spingler
authors.forename: Roger
authors.initials: R
authors.lastname: Alberto
authors.forename: Henrik
authors.initials: H
authors.lastname: Braband
mesh_terms: D018360:Crystallography, X-Ray; D006571:Heterocyclic Compounds / Q000737:chemistry*; D008697:Methane / Q000031:analogs & derivatives* / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013667:Technetium / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D006571:Heterocyclic Compounds; D009942:Organometallic Compounds; D014867:Water; C030011:carbene; D013667:Technetium; D008697:Methane