Synthesis and Spectroscopic Studies of Mixed Ligand Complexes of Pt ( II ) and Pd ( II ) with Ethyl-α-Isonitrosoacetoacetate and Dienes

The mixed ligand complexes of the kind [M(L1) (L2)] where M= Pt(II), Pd(II).L1 = primary ligand ethyl-α-isonitrosoacetoacetate derived from reaction between ethyl acetoacetate, acetic acid and sodium nitrite and L2=secondary ligand para-phenyldiamine (PPD) are synthesized. All the prepared complexes were identified and confirmed by elemental analysis, molar conductance measurements, and infrared electronic absorption. Their complexes has been made based on elemental analysis, molar conductivity, UV-Vis, FT-IR and HNMR spectroscopy and magnetic moment measurements as well as thermal analysis (TGA and DTA). The elemental analysis information recommends that the stoichiometry of the complexes to be 1:2:1. The molar conductance measurements of the complexes indicate their non-electrolytic nature. The infrared spectral information showed the coordination sites of the free ligand with the central metal particle. The electronic absorption spectral information disclosed the existence of an octahedral geometry for Pt(II) and Pd(II) complexes.


INTRODUCTION
Metal ions play important role in a very huge variety of biological processes.The ions with biologically active ligands square measure are of appreciable interest.Some of these compounds act via chelation [1].The coordination chemistry of transition metal complexes with mixed ligands are of current interest because they can give new materials with helpful properties like magnetic exchange [2][3] electrical physical phenomenon [4], photoluminescence [5], nonlinear optical property [6], and antimicrobial activity [7].The biological importance of mixed ligand complexes is that they are more effective than the free ligands [8].Mixed ligand complexes containing nitrogen and oxygen donors are important owing to their antifungal bactericide and antitumor activities [9].
In the present paper we synthesize and characterize the Pt(II), Pd(II) mixed ligand complexes with primary substance Ethyl-α-isonitrosoacetoacetate and secondary ligand para phenyl diamine.

Physical Measurement
Solvents and chemicals used for the synthesis were of analytical grade.
The FT-IR spectra recorded in the range 4000-400 cm -1 on a FT-IR spectrophotometer as KBR discs.The NMR spectra were measured using Varian Gemini 200-200 MHz spectrophotometer and the spectra were recorded from 0-15 ppm using TMS as an internal standard in dimethylsulfoxide (d6-DMSO) as the solvent.Thermal analysis (TG and DTG) were obtained in a nitrogen atmosphere using a type TGA 50 of Shimadzu deviatograph thermal analyzer.The molar conductivities were carried out using a Jenway 4310 conductivity meter.Electronic spectra were recorded in the range 200-800nm, on jasco V-530 UV-Vis, spectrophotometer.A Perkin Elmer 240C elemental analyzer was used to collect micro analytical data (C, H, N).

Synthesis of Ethyl-α-isonitrosoacetoacetate (HEINA):
The reagent Ethyl-α-isonitrosoacetoacetate (HEINA) is also known as ethyloximimoacatoacetate, it is synthesized by following procedure [10][11].Ethyl acetoacetate 1.4 moles and 3.5 mole of glacial acetic acid were taken in three naked round bottom flask fitted with thermometer, reflux condenser and mechanical stirrer and cooled in ice bath at 0 0 C and a solution of 95 % sodium nitrite was added over a period of one hour and temperature being kept between 5 0 C to 10 0 C.This mixture mixed with double distilled water, stirring for two hours and extracted with ether.
After drying ether solution with sodium sulphate the solvent was distilled off on a steam bath the crude product was dissolved in toluene and cooled to -13 0 C to -15 0 C. The separated white crystals were filtered, washed and analyzed.

Synthesis of Pd(EINA)2PPD:
The metal complex was prepared in alcoholic Palladium Chloride solution (0.177 g, 0.1 mol), adding HEINA (0.318 g, 0.2 mol in water: alcohol 1:1 v/v previously prepared) and after the para-phenyldiamine (0.108 g 0.1 mol in water: alcohol 1;1 v/v), by correcting the pH to 5.5 to 6. Then the solution was kept in a boiling water bath for 30 minutes.The red colored complex was crystallized from chloroform yield 78% FT-IR (KBr, cm The general structure of metal ligand complex is as follows.

RESULTS AND DISCUSSION
The elemental analysis shown in table-1 indicates that all the metal complexes have 1:2:1 stoichiometry and are dark in color, soluble in DMF and DMSO.The molar conductance values obtained for these complexes at the concentration of 10 -4 is in the range of 9.5 to 10.2 ohm -1 mo1 cm 2 .These values are too low to account for any dissociation of the complexes can be regarded as non-electrolyte.Square planer complexes of palladium and platinum (II) are diamagnetic while octahedral complexes are paramagnetic in nature [12][13].The Pt(II) complexes were found to paramagnetic indicating octahedral coordination of ligands around Pt(II) ion.The Pd(II) complexes exhibit magnetic moment in the range of 2.91 BM suggestive of octahedral nature for these complexes.IR spectra of the complex were compared with those of the HEINA in order to find out the point of attachment of the HEINA.The IR spectra of the free HEINA showed a strong absorption at around 3441cm - 1 due to the N-OH stretching.This absorption is shifted to lower frequency in the complex indicating the coordination of N-OH to metal ion.The presence of a band in the region 1690 cm -1 is another indication of the involvement of ester group in coordination.The -C=O band that appeared at around 1745cm -1 in the HEINA.This absorption is shifted to the lower frequency region 1665 cm -1 which may be attributed to the coordination through the oxygen atom in metal complex.H NMR spectra of both the Pt(EINA)2PPD and Pd(EINA)2PPD complexes have been recorded in EtOD solution.In the 1 HNMR spectra of ligand HEINA a sharp singlet at 8.65 ppm is observed which may be assigned to N-OH.Absence of this signal in the spectra of the metal complex confirms the coordination through N-OH group.The signal due to the CH3 proton in the spectra of the HEINA undergoes a downfield shift in the spectra of the complexes at σ = 2.50-2.55ppmconfirming the coordination through N-OH.The signal due to CH2 -CH3-protons is a singlet at σ = 4.224-1.375ppm.While the aryl protons of the compound gave a signal at σ = 6.6 ppm.

Pd(EINA)2PPD Complex
The TGA curve of compound Pd(EINA)2PPD shows a significant reduction in weight (25%) due to decomposition of compound at lower temperatures.The resulting decomposed compounds are not stable to heat and losing their weight gradually up to 700 0 C.

CONCLUSION
The Elemental analysis, Magnetic susceptibility, Electronic and 1 HNMR, FTIR observations suggest that the octahedral geometry for Pt(II) and Pd(II) complexes and exhibit coordination number six.The general structure of the complex is shown in Figure 1.
The results of DTA curve show an endothermic peak at 441.24 0 C which indicates the formation of stable compound from decomposition of Pd(EINA)2PPD.The resulting compound undergoes decomposition above 700 0 C both in DTA & TGA by forming oxides of palladium at 480.27 0 C. Thermal activation energy was 31.91 J / Mole and order of reaction was 1.

Table 1 .
Elemental analysis and magnetic moment of the complexes.

Table 2 .
IR Assignments of Metal Complexes.

Table 3 .
Elemental Analysis and Magnetic Moment of the Complexes.