Synthesis and characterization of complexes of the {ReO}3+ core with SNS and S donor ligands

The reaction of [ReOCl3(PPh3)2] with N,N-bis(2-mercaptoethyl)benzylamine and 4-bromobenzenethiol allowed for the isolation of [ReO{η3-(SCH2CH2)2N(CH2C6H5)}-(η1-C6H4Br-4-S)] (1). The reaction of [ReOCl3(PPh3)2] with [(HSCH2CH2)2N(CH2C5H4N)] and the appropriate thiol in chloroform treated with triethylamine has led to the isolation of a series of neutral rhenium complexes of the type [ReO{η3-(SCH2CH2)2N(CH2C5H4N)}(η1-C6H4X-4-S)] (X=Br (2), Cl (3), F (4), and OCH3 (5)) and [ReO{η3-(SCH2CH2)2N(CH2C5H4N)}(η1-C6H4OCH3-4-CH2S)] (6). Likewise, under similar reaction conditions, the use of the related tridentate ligand, [(HSCH2CH2)2N(CH2CH2C5H4N)], has led to the isolation of a series of rhenium complexes of the type [ReO{η3-(SCH2CH2)2N(CH2CH2C5H4N)}(η1-C6H4X-4-S)] (X=Br (7), Cl (8), OCH3 (9)), as well as [ReO{η3-(SCH2CH2)2N(CH2CH2C5H4N)}(η1-C6H4Cl-4-CH2S)]·0.5CH3(CH2)4CH3 (10). These compounds are extensions of the ‘3+1’ approach to the synthesis of materials with the {MO}3+ core (M=Tc and Re), which have applications in nuclear medicine. The ligands chosen allow systematic exploration of the consequences of para-substitution on the monodentate thiolate ligand [S] and of derivatization of the substituent R on the tridentate aminodithiol ligand [SNS] of the type (HSCH2CH2)2NR. Such modifications can influence lipophilicity, charge, size and molecular weight of the complex and consequently the biodistribution.