Novel N -benzimidazolyl-2-thione o -tosylamino(hydroxy)azomethinic tautomeric ligand systems and their metallochelates

Novel ligand systems –azomethinic derivatives of 1-amino-3-methyl-1,3-dihydrobenzoimidazole-2-thione and o -tosylamino(hydroxy)benzaldehydes – are synthesized as a result of a multistage procedure and are evaluated. Study of the coordination activity of these compounds has shown that they form complexes ML 2 with transition d -elements containing MN 4 S 2 and MN 2 O 2 S 2 coordination units in solid and in solution. Electrospray mass-spectrometry results show the possibility of formation of M 2 L 2 and M 2 L 3 complexes in the vapor phase.


Results and Discussion
The synthesis of type 1 compounds has been carried out following the transformations 10,11 described in Scheme 1.][15][16] Metallocomplexes, gained on the basis of 1, by analogy with chelates of 2-amino(oxo-, thio)azoles 17 -26 and o-amino(hydroxy-, mercapto)azomethines 5,16,27 could be represented by formulas 2a and 2b.Both of these types are possible considering the elemental analysis data.Electrospray mass-spectrometry indicates mononuclear chelates with structure L 2 M (LHligand). 28ormations of chelate structures are confirmed by comparison of IR spectra of ligands 1 and complexes 2. Thus, disappearance of the signals of the HNTs and OH groups (3300 cm -1 region) and lower frequencies of azomethinic С=N group (by 15-25 cm -1 from 1597 cm -1 ) and С=S (by 25-60 cm -1 from 1186 cm -1 ) are observed.The last fact confirms an octahedral structure 2b in the described mononuclear complexes.This conclusion is also confirmed by magneto chemical data (2: Х = NTs, M = Co, µ eff = 4.63 M.B.; M = Ni, µ eff = 2.87 M.B.) and electron spectroscopy results (2: Х = NTs, M = Ni; bands at 14580 cm -1 (ε = 25 l/mol .cm) and 9500 cm -1 (ε = 47 l/mol .cm), corresponding to the transitions 3 А 2g → 3 T 2g and 3 А 2g → 3 T 1g (F) of nickel(2+) ion in the symmetry О h ).However, the absorption of the C=S group represented by double set of bands in the IR spectrum of copper chelates (2: X = NTs, O; M = Cu) may be caused by a pentacoordinated structure with participation of only one sulfur atom of two ligands in the coordination.
Electrospray mass-spectrometry research has not only allowed 28 to detect complexes of ML 2 structure, but also to establish the formation of binuclear complexes for all metallochelates of copper, and in some cases for nickel and cadmium.Besides in electrospray mass-spectra, the ions containing three ligands and two atoms of metal -M 2 L 3 , were also detected (Table 1).The ions mentioned above can be demonstrated by the mass-spectrum (fig. 1) of copper complex 2 (X = O, M = Cu).As we can see in the spectrum (Fig. 1) alongside with the presence of the molecular ion (m/z = 629), there is a set of peaks corresponding to M 2 L 2 and M 2 L 3 binuclear complexes structures.The structure of a binuclear M 2 L 2 complex can be presented by formula 3, expanding the number of active coordination centers (X=NTs, O).
Thus, o-tosylamino(hydroxy)azomethinic derivatives of 1-amino-2-thio-3methylbenzimidazole during complexation with d-metals in solution act as bi-and tridentate ligands forming ML 2 complexes, opening a novel way for the introduction of a chalcogen atom in the coordination sphere.From the other hand these systems may play the role of mono-, biand tridentate ligands in vapor phase forming M 2 L 2 and M 2 L 3 complexes.

Experimental Section
General Procedures. 1 H NMR spectra (DMSO-d 6 ) were registered on Varian UNITY-300 (300 MHz, internal 2 H standard) and Bruker DPX-250 (250 MHz, internal 2 H standard) spectrometers.Mass-spectra (electrospray ionization method) 29 were obtained on a mass-spectrometer Water/Micromass ZQ (Manchester, UK) equipped Harvard Apparatus.Methanolic solutions of complex samples were introduced with the flow speed 20 of µL/min.Capillary potential was 3 kV, lens potential -0.5 kV, extractor potential -4 V.The source temperature was 120 °C and the temperature of desolvation was 300 °C.Nitrogen was both used as spray gas and desolvating gas.IR spectra as Nujol mulls or KBr pellets were registered on Nicolet Impact-400.The electron spectra of the solutions of complexes in CH 2 Cl 2 were measured on UNICAM Helyos Gamma.Magnetic susceptibilities of chelates were measured by Evans method.

Table 1 .
Peaks containing in mass-spectra of ligands 1 and their complexes 2