Synthesis of carbon-11 radiolabelled transition metal complexes using 11 C-dithiocarbamates

A novel radiolabelling method exploiting 11C-dithiocarbamate ligands has been used to generate 11C-labelled Au(I), Au(III), Pd(II) and Pt(II) complexes in high radiochemical yields (71-99%). Labelled complexes were prepared in a rapid one-pot procedure via the substitution reaction of 11C-dithiocarbamate ligands with appropriate transition metal chloride precursors.


General radiochemistry and chemistry considerations
Radiolabelling reactions were performed in a lead-lined hot cell using a custom-built methylation apparatus consisting of an externally controlled valve array, heater block and magnetic stirrer. Analysis of crude radioactive reaction mixtures was performed via HPLC using an Agilent 1100 system with in-line radioactivity and diode array detectors (UV) and an Agilent Eclipse XDB-C18 column (
The solution was then extracted with chloroform (5 mL), dried over MgSO 4 and evaporated to dryness to obtain a white solid (41 mg, 59 %). 1
Single crystals suitable for X-ray diffraction were obtained via diffusion of diethyl ether into a chloroform solution of the complex. 1

[ 11 C]Carbon disulfide production
[ 11 C]carbon dioxide was produced using a Siemens Eclipse HP cyclotron via the 14 N[p,α] 11 C nuclear reaction of 11 MeV proton bombardment of a gaseous target containing nitrogen and 1% oxygen. Cyclotron bombarded was typically set at 15 μA for 5 minutes. [ 11 C]CH 3 I was produced via [ 11 C]CO 2 the gas phase H 2 reduction reaction over Ni catalyst and high temperature free-radical iodination of [ 11 C]CH 4 using a commercially-available Synthra unit. Retention of radioactivity in the S 8 /sand column (green) and the reaction vial (purple). Note: The intensities of graphs are not quantified and correlated, as the detectors are not positioned at precisely the same distance from the column and reaction vial. Axes represent the arbitrary radioactivity units (mV) versus time (min).

Radiosynthesis of 11 C-labelled Au(III) and Au(I) complexes
Gaseous [ 11 C]CS 2 was produced as described above and passed into a solution of diethylamine or dibenzylamine (5 mg) in acetonitrile (1 mL) to generate [ 11 C]diethyldithiocarbamate or [ 11 C]dibenzyldithiocarbamate in situ.
The preparation and radioHPLC analysis of        The C50-based included dichloromethane solvent molecule in the structure of 9 was found to be disordered. Two orientations were identified of ca. 83 and 17% occupancy, their geometries were optimised, the thermal parameters of adjacent atoms were restrained to be similar, and only the non-hydrogen atoms of the major occupancy orientation were refined anisotropically (those of the minor occupancy orientation were refined isotropically).