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

Abstract

The reaction of [ReOCl(3)(PPh(3))(2)] with N,N-bis(2-mercaptoethyl)benzylamine and 4-bromobenzenethiol allowed for the isolation of [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)C(6)H(5))}-(eta(1)-C(6)H(4)Br-4-S)] (1). The reaction of [ReOCl(3)(PPh(3))(2)] with [(HSCH(2)CH(2))(2)N(CH(2)C(5)H(4)N)] 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{eta(3)-(SCH(2)CH(2))(2)N(CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)X-4-S)] (X = Br (2), Cl (3), F (4), and OCH(3) (5)) and [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)OCH(3)-4-CH(2)S)] (6). Likewise, under similar reaction conditions, the use of the related tridentate ligand, [(HSCH(2)CH(2))(2)N(CH(2)CH(2)C(5)H(4)N)], has led to the isolation of a series of rhenium complexes of the type [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)X-4-S)] (X=Br (7), Cl (8), OCH(3) (9)), as well as [ReO{eta(3)-(SCH(2)CH(2))(2)N(CH(2)CH(2)C(5)H(4)N)}(eta(1)-C(6)H(4)Cl-4-CH(2)S)].0.5CH(3)(CH(2))(4)CH(3) (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 (HSCH(2)CH(2))(2)NR. Such modifications can influence lipophilicity, charge, size and molecular weight of the complex and consequently the biodistribution.

An unexpected ‘4+2’ [N3S]/[NS] rhenium(IV) complex formed upon cleavage of a Re(V) imido bond

“…The accessibility of multiple oxidation states of Tc and Re, −3 to + 7 [8], makes it possible to accommodate a variety of polydentate, multi-anionic ligands. The most successful strategy to the development of diagnostic imaging agents of Tc and potential therapeutic reagents based on Re has exploited ligands to stabilize the oxometal [MO] 3+ core (where M = Tc and Re), utilizing tetradentate N x S( 4−x ) (x = 0 to 3) chelates [9], '3+1' [10] and '3+2' [11] mixed thiolate ligands. However, the recent introduction of technetium and rhenium complexes with alternative functional cores, such as diazenido-, hydrazido-, imido-and nitrido- [12], at the 'carrier free' level has made this class of compounds featuring M-N multiple bonds more attractive for the development of 99m Tc and 186/188 Re radiopharmaceuticals, whose production had been focused in the past primarily on oxometal complexes(Scheme 1).…”

Synthesis and characterization of a {ReO}3+ complex with S- and N-donor ligands and of its 99m Tc analog

“…The rhenium atom is displaced by 0.031 Å above the equatorial plane in the direction of thiolate. On the whole, the geometry is typical for six-coordinate Re/Tc(V) complexes [21].…”

“…This value is at the lower end of the range observed for the [ReO] 3+ core, suggesting that the Re-OH bond competes effectively. The Re-N bond length (2.0531 Å) is typical for Re-N single bonds with N atoms exhibiting sp 3 hybridization [18,21]. The Re-S bond length (2.355 Å) is typical for Re complexes with S-donor ligands in the equatorial plane, whereas axial Re-S bonds are somewhat longer (2.39 Å).…”

Two mononuclear Tc complexes: [2,2′-(3-phenylpropylimino)- and [2,2′-(propylimino)bis(ethanethiolato)](4-methoxybenzenethiolato)oxidotechnate(V)

“…1 and 2). Similar Re complexes are currently under study for various applications (Bouziotis et al, 1999;Chelminiak et al, 2005;Femia et al, 2000;Friebe et al, 2000;Heimbold et al, 2002;Jung et al, 2002;Maresca et al, 2002;Marsh, 2005;Papadopoulos et al, 1999;Tsoukalas et al, 1999). In the case of the title compounds, the Tc atom is coordinated by two S atoms and an N atom from the tridentate ligand, another S atom provided by the 4-methoxybenzenethiolate ligand and an additional oxide O atom to complete the coordination environment.…”