942985-25-3Relevant academic research and scientific papers
Rhenium and technetium complexes with N,N-dialkyl-N′-benzoylthioureas
Nguyen, Hung Huy,Abram, Ulrich
, p. 5310 - 5319 (2008/10/09)
N,N-Dialkyl-N′-benzoylthioureas, HR1R2btu, react under single deprotonation and form air-stable chelate complexes with common rhenium or technetium complexes such as (NBu4)[MOCl 4] (M = Re, Tc) or [ReOCl3(PPh3)2]. Compositions and molecular structures of the products are strongly dependent on the precursors used and the reaction conditions applied. Reactions with [ReOCl3(PPh3)2] in CH2Cl2 give complexes of the general formula [ReOCl2(R1R 2btu)(PPh3)] (3), with the benzoyl oxygen atom of the chelating benzoylthiourea being trans to the oxo ligand, and/or Re(III) complexes of the composition [ReCl2(R1R 2btu)(PPh3)2] (4) with the PPh3 ligands in trans positions to each other. In polar solvents such as MeOH, EtOH or acetone, corresponding reactions without addition of a supporting base only result in intractable brown solutions, from which no crystalline complexes could be isolated. The addition of NEt3, however, allows the isolation of the bis-chelates [ReOCl(R1R2btu)2] (1) in good yields. In this type of complex, one of the chelating R1R 2btu- ligands coordinates equatorially, while the second occupies the position trans to the oxo ligand with its oxygen atom. The latter compounds can also be prepared from (NBu4)[ReOCl4] in MeOH when no base is added, while the addition of NEt3 results in the formation of [ReO(OMe)(R1R2btu)2] (5) complexes with the methoxo ligand trans to O2-. Compounds of the type 5 can alternatively be prepared by heating 1 in MeOH with addition of NEt3. A reversible conversion of 5 into oxo-bridged dimers of the composition [{ReO(R1R1btu)2}2O] (6) is observed in water-containing solvents. Starting from (NBu4)[TcOCl 4], a series of technetium complexes of the type [TcOCl(R 1R2btu)2] (2) could be prepared. The structures of such compounds are similar to those of the rhenium analogues 1: Reduction of 2 with PPh3 in CH2Cl2 gives Tc(III) complexes of the composition [TcCl(R1R2btu)2(PPh 3)] (7) having the chloro and PPh3 ligands in cis positions. When this reaction is performed in the presence of excess chelating ligand, the Tc(III) tris-chelates [Tc(R1R2btu) 3] (8) are formed.
