Synthesis and Characterization of Co (II), Ni (II), Cu (II), and Pd(II) Complexes with Mono Sodium 2,4,6-Trioxotetrahydropyrimidine-1(2H)- Carbodithioate

Mono sodium 2,4,6-trioxotetrahydropyrimidine-1(2H)-carbodithioate (L) was prepared from barbituric acid with carbon disulfide (CS2) in the presence of sodium hydroxide, then reacted with some chloride metals to synthesis a complexes of the types [M (L) Cl (H2O)3], [M (L)2(H2O) 2] and [M(L)2] {M= Co(II), Ni(II), Cu(II)}, and [Pd (L)(H2O)2]Cl and[Pd (L)2] . These compounds were characterized using infra-red spectra FTIR, electronic spectra UV– VIS, proton nuclear magnetic resonance H-NMR spectroscopy, Micro Elemental Analysis, and Magnetic Measurements.These measurements indicate that the prepared complexes have octahedral, square planer or tetrahedral geometry. Molar Conductance measurements shows all the prepared complexes are non-electrolytic except the palladium complex of the type [Pd(L)(H2O)2]Cl.


Introduction
Organic chemistry of dithiocarbamates have attracted a wonderful deal of importance because of their exciting chemistry and huge effectiveness.Dithiocarbamates, are chelating agents with various applications, cytotoxic properties, chelating agent for the extraction of trace metals, have been used in against metal poisoning [1][2][3] and different various applications in agriculture, medicinal drug, industry, analytical and organic chemistry [2,3] .Its complexes show improved antibacterial, antimalarial, and fungicidal activities as compared to free ligands because of recede in polarity of metals after complexation [4,5] .
Dithiocarbamate ligands can coordinate to all the transition elements in order to stabilize lowor high-valent metal ions [6] .Dithiocarbamates have specific binding modes to metal ions (figure 1).It acts as a chelate ligand (1) via two sulfur atoms [6] , and monodentate coordination mode (2) is also particularly common [7] .In a few cases the two metal sulfur bonds are quite exceptional but nonetheless within the anticipated variety for a bonding interaction.That is commonly termed the anisobidentate coordination mode (3) [8] .All other binding modes (4-6) involve the dithiocarbamate bridging two or extra metal atoms, as much as a maximum of four [9] .

Chemicals and Instruments
Reagent grade barbituric acid (B.A) and sodium hydroxide were procured from Alfa aesar.
The infra-red spectra of ligand and metal complexes spectra were recorded by SHIMADZU spectrophotometer within the range (400-4000 cm -1 ).The electronic spectra of the complexes were recorded in SHIMADZU 2450 UV-VIS as 10 -3 M DMSO solution.The magnetic susceptibilities were measured at room temperature by using Sherwood scientific instrument (Evans balance).Conductivity measurements were recorded by using dimethyl sulphoxide (DMSO) as a solvent for 10 -3 M solution of the complexes at room temperature, using (Consort C832) instrument.The 1 H-NMR measurements were measured by using DMSO-d 6 as solvent in Bruker MHz-Avance III instrument (300 MHz) and the micro element analyses The ligand was prepared according to typical method [10][11][12][13] .A solution of Barbituric acid To aqueous solution 8ml of (L) (0.6mmol), a solution of (0.6mmol) of Co (II), Ni (II) and Cu (II) salts correspondingly, in 5 ml distilled water, was added drop wise under stirring.The reaction mixture was refluxed for 1 hour on steam bath, and then was filtered; the resulting colored precipitate was washed with hot distilled water and dried at 60 o C for 4 hours.
To 10ml concentrated HCl 37%, (2g, 11.An aqueous solution 20 ml of Na2PdCl4 (0.177g, 0.6 mmol) was added to an aqueous solution 30 ml of (L) (0.2g, 0.6 mmol), this mixture was refluxed for 4 hours.The obtained brown solid was then washed with hot distilled water and dried at 60 o C for 4 hours.

Preparation of [Pd (L)2] complex.
An aqueous solution 20 ml of Na2PdCl4 (0.177g, 0.6 mmol) was added to an aqueous solution 30 ml of (L) (0.4g, 1.2 mmol), this mixture was refluxed for 4 hours.The obtained brown filtered was then evaporated to gives dark brown solids, washed with hot distilled water and dried at 60 o C for 4 hours.

Results and Discussion
The Dithiocarbamate ligand and its Co(II), Ni(II), Cu(II) and Pd(II) complexes have been synthesized and characterized using IR spectra, electronic spectra, magnetic susceptibility, conductivity measurements, 1 H-nuclear magnetic resonance, micro element analyses, and the atomic absorption.
The physical properties of ligand and its complexes are listed in Table 1.All complexes are thermally stable and have a good solubility in DMSO and DMF.The molar conductivities of 10 -3 M solution of all complexes (Table1) indicate that they are non-electrolytes except [Pd (L) (H2O)2]Cl [15].

IR Spectra:
The coordination modes of the ligand to the metal ions have been investigated by comparing the infrared spectra of the free ligand with its metal complexes (Table 2).The band of C..N) was appeared at 1458 cm -1 in free ligand and shifted towards high values at rang in the spectra of the complexes [16][17][18] .The two bands of  (C..S) of the ligand appeared at 1033 and 933 cm -1 , as well as  (C..S) in all complexes shifted towards lower values.We noticed all complexes show a single peak at the range (991-1030) cm -1 [19,20] ,that is mean the ligand is bidentate through two sulfur atoms.The bands at (418-475) cm -1 could be attributed to υ (M-OH2) [21] .
Electronic Spectra: The electronic spectra of the complexes were recorded as 10 -3 M solution in DMSO and the results presented in Table 3.The electronic spectra of four coordinated Co(II) complex exhibited one absorptions at (15313) cm -1 which was assigned to ( 2 A1g  2 Eg) in a distorted tetrahedral geometry around cobalt (II).The electronic spectra of four coordinated Ni(II) and Pd(II) complexes shows two absorption at (24194, 23818-23773) cm -1 and (15576, 15822-15757) cm -1 respectively, assigned to 1 A1g 1 B1g and 1 A1g  1 A2g.These bands are in agreement with square planar nickel (II) and palladium complexes [22,23] .The electronic spectra of the prepared four coordinated copper (II) complex gives broad absorption band at (15124) cm -1 , which can be assigned to the combination of transitions ( 2 B1g  2 A1g) and ( 2 B1g  2 Eg).The position of these bands is in agreement with four coordinated copper (II) complexes with square-planar geometry [22,24,25] .The electronic spectra of six coordinated Co(II) complex exhibited two absorptions bands at (15667-16007) cm -1 and (20167,20100) cm -1 which was assigned to ( 4 T1g  4 A2g) and ( 4 T1g  4 T1g(p)) in octahedral geometry around cobalt (II).The electronic spectra of six coordinated Ni(II) complexes shows three absorption bands at (11733-12001,13024-13330,27373-25100) cm -1 , assigned to 3 A2g 3 T2g( 1) , 3 A2g  3 T1g and 3 A2g  3 T1g(p).These bands are in agreement with octahedral nickel (II) complexes [22,23] .The electronic spectra of the prepared six coordinated The experimental magnetic moment for each complex is listed in Table 1.The magnetic moment give an idea about the electronic state of the metal ion in the complex.The magnetic moment of six coordinated complexes are, Co (II) complexes are (5.01,5.00) B.M respectively [28] , for Ni (II) complexes are (2.98,3.01) B.M [29,30] .For Cu (II) complexes are (1.81,1.99) B.M [31] .These values are due to the presence of octahedral configuration for these complexes, while the magnetic moment of four coordinated complexes are, Co (II) complex is (2.40) B.M this indicate that cobalt has distorted tetrahedral structure [28] , but Ni (II) and Pd(II) gives no value, that is indicate that nickel and palladium complexes have square planar geometry, while Cu (II) complex is (1.66)B.M, this value is appropriate for square planar complex [29,30] .As shown in table 1.

Proton nuclear magnetic resonance ( 1 H-NMR) Spectra Measurements:
1 H-NMR spectra (figure 6-8), the NaBADTC shows a single signal at (3.505ppm) with integration 1.96 .This signal is a good proof to the existence of (CH2), another signal at (10.92 ppm) with integration equal 1.00 refers to the proton of NH as in figure (6).The 1 H-NMR of [Pd(L)(H2O)2].Cl complex shows a single signal at (2.960 ppm) with integration 2.02 while the proton of NH gives integration equal 1.00 at (10.93ppm), we must mentioned that two water molecules which might possibly be replaced by DMSO molecules when the complex is dissolved in this solvent.as in figure (7), while the 1 H-NMR of the complex

( 0 .
4g, 3 mmol) in (20 ml) DMSO was added to CS2 (0.235g, 3.1mmol) in the presence of NaOH (0.125 g, 3 mmol).The reaction was maintained at 5 • C using a water-ice bath.This mixture was subjected to continuous stirring for 1 hour and maintained at room temperature for three weeks till beige solid was formed.The obtained solid was filtered, recrystallized from (3:1 (90%ethanol): Chloroform) and dried in a vacuum oven at 40 O C for 4 hours.Preparation of [M (L) Cl (H2O) 3] complexes.M= Co (II), Ni (II) and Cu (II).
6 mmol) Co (II), Ni(II) and Cu(II), correspondingly, in 5 ml distilled water, was added drop wise under stirring.The reaction mixture was refluxed for 2 hours on steam bath, filtered, the resulting colored precipitate was washed with hot distilled water in order to remove unreacted (L and metal salts) and dried at room temperature.Preparation of [M (L)2] complexes.M= Co (II), Ni (II) and Cu (II).These complexes were prepared by drying complexes of the type [M (L)2 (H2O) 2] at 100 o C for 24 hours.
3mmol) PdCl2 was added slowly with continuously stirring by glass rod in a hot water bath, till the total volume reduced to the one-third of its volume, a saturated aqueous solution (1.32g, 22.6mmol) of NaCl was added slowly with continuously stirring by glass rod in water bath, after that the solution was left until became deep red brown powder, the obtained powder was washed three times with diethylether and dried at 60 o C for three hours in oven.Preparation of [Pd (L) (H2O)2]Cl complex.
copper (II) complexes give absorption band at (14233-14400 and 16051-16377) cm -1 , which can be assigned to the combination of transitions ( 2 B1g  2 A1g) and ( 2 B1g  2 Eg).The position of these bands is in agreement with six coordinated copper (II) complexes with octahedral geometry.

[
Pd(L)2] gives a single signal at (3.024ppm) with integration 4.06 attributed to two CH2 groups from and another signal at (10.72ppm) with integration equal 1.91 due to presence of two NH group from two ligand which attached to the same palladium Figure8.

2 .
These complexes showed diversity in there geometry, which were octahedral geometry in the complexes of the type [M(L)(H2O)3Cl], [M(L)2(H2O)2], and square planar in the palladium complexes.When [M(L)2(H2O)2] dried at 140 oC under vacuum give the complexes of the type [M(L)2] which show square planar structure where {M= Pd,Ni,Cu} whilst [Co(L) 2] showed a tetrahedral structure.