Synthesis and Characterization Complexes of Cobalt(II), Nickel(II), Copper(II) and Palladium with [N ' -{2-(4-isobutyl-phenyl)-propionyl} pyridine-4-carbohydrazide]

This research concern with the metal complexes of the ligand [N ' -{2-(4-isobutyl-phenyl)-propionyl}pyridine-4-carbohydrazide] with Co(II), Ni(II) , Cu(II) and Pd(II) have been synthesized and characterized by atomic absorption , infrared, electronic spectra, molar conductivity and magnetic moment measurements. On the basis of the data obtained from the above measurements, the ligand act as a neutral bidentate and the octahedral structures are proposed for the Co(II), Ni(II) and Cu(II) while the square planer structures are assigned to Pd(II) complexes.

Aroylhydrazine ligands have recently gained the increasing concern due to their quite interesting chemical properties [1,2].Most of the studies were focused on unsymmetrical aroylhydrazines, used as ligands for coordination to metal ions, due to the tautomeric effect of the enol form and keto form, several electron-rich donor centers, variable bonding modes, structural diversity and promising biological implications [3][4][5][6].As regards biological implications, complexes with these ligands have been intensively investigated for antitumoral, antimicrobial and antiinflammatory activities.The inhibitory action is attributed due to their chelating properties [7,8].In view of our interest in metal complexes with a variety of multidentate acylhydrazines [9], we report here in the synthesis and characterization of [N ' -{2-(4isobutyl-phenyl)-propionyl}pyridine-4carbohydrazide] (LH), which represents a prototype of new of asymmetric ligands, which combine two donor functionalities in one molecule (ibuprofen acid chloride and Isoniazid).In order to further investigate the coordination modes of (LH) with transition metals and to study the chemistry of its complexes, we synthesized and characterized and their Cu(II), Co(II), Ni(II) and Pd(II) complexes (Scheme 1).These studies have been mainly directed towards identifying the groups directly attached to the metal site and establishing the structure of the coordination compounds thus formed.

Synthesis of the complexes.
(1,3,4,6,7, 9 and 10 complexes) These complexes were prepared using CoCl and Na 2 PdCl 4 salts scheme(1).The ethanolic solution of metallic salt (1 mmol/5 mL ethanol) was mixed with stirring with a hot clear ethanolic solution of the ligand (LH) (2 mmol/20 mL ethanol).After stirred the solution for 3 hrs, Then cooled down to room temperature.The resulting solution, was filtered off and set aside for slow evaporation at room temperature.A precipitates were filtered, washed successively with water and diethylether and finally dried in oven.( A hot ethanolic solution of metallic salt (1 mmol/5 ml ethanol) was mixed with stirring with a hot clear ethanolic solution of the ligand (LH) (2 mmol/20 ml ethanol).A few drops of triethylamine (Et 3 N) was added to the solution with stirring.The mixtures were refluxed for 3 hours.The solid precipitates were filtered off, washed in ethanol , distilled water and dried.The solid precipitates were recrystallized from DMSO.

3.Results and Discussion
The ligand and it's metal complexes were insoluble in water but soluble in organic solvents such as DMSO,DMF the metal percentage in the complexes and physical data of ligands and complexes were given in table (1).The IR spectra of all the complexes were listed in table (2), and compared with that of the ligand to study the structural changes in the ligand upon complexation.The IR spectra of the complexes showed bands at 3387-3444 cm -1 due to (O-H).In the IR spectra of the complexes showed a medium intensity band at 1602-1620 cm -1 due to (C=O), shifted to lower frequencies compared with that of the ligand, this indicates that C=O group is participate in coordination to metal ions [10].There is a medium intensity band at 1597 cm -1 in the IR spectrum of ligand due to C=N group, with shifted lower frequency at 1546-1566 cm -1 , this indicates that C=N groups is participate in coordination to metal ions [11] .New strong intensity bands appears 1180-1215 cm -1 due to (C-O) group [12] .A new strong intensity bands at 1381-1392cm -1 3,6 and 9 complexes in the spectra of the complexes which assigned to stretching frequency of υ(NO 3 ) bond [13 ].The appearance of bands in the IR region at 410-443 cm -1 in the complexes may be assignable to M-N frequency.Additional bands in the complexes in the region 474-549cm -1 compared with IR spectrum of free ligand have tentatively been assigned to M-O bond [14,15].From the obtained results it is clear that the metal ions associated with ligand through oxygen atom of one carboxyl groups and nitrogen atom of one amide groups.
(2,5 and 8) complexes The IR spectrum of the ligand shows band at 3305 cm -1 due to the NH group, IR spectra of the prepared complexes showed disappeared of this band that mean not found N-H in these complexes.The (C=O) band was disappeared in spectra of these complexes.There is one medium intensity bands at 1597 cm -1 in the IR spectrum of ligand due to C=N group , and this was shifted to lower frequencies at 1548 -1566 cm -1 , this indicates that C=N groups is participate in coordination to metal ions.New strong intensity bands at 1604-1610 cm -1 due to new C=N.New strong intensity bands appears 1172-1219 cm -1 due to (C-O) group [11].The stretching vibration of the CH group observed at 3029-3053cm -1 and 2954-2978cm -1 the aromatic and aliphatic respectively.The IR spectra of the complexes exhibit a broad band's centered at 3402-3425 cm −1 due to the symmetric and asymmetric stretching modes of coordinated H 2 O. Weak bands in the 934 -945 cm -1 in complexes, and these bands represent the coordinated water [16] .The appearance of bands in the IR region at 403-443 cm -1 in the complexes may be assignable to M-N frequency.The appearance of new bands in the complexes in the region at 501-564 cm -1 compared with IR spectra of free ligand have tentatively been assigned to M-O bond [17,18].(10) complex.In the IR spectrum of [Pd(L3H) 2 Cl 2 ] complex( 10) showed strong band at 3442 cm -1 due to OH ,as well as the disappearance of the N-H groups and also disappearance of C=O in spectrum of complex.There is one medium intensity band at 1597 cm -1 in the IR spectrum of ligand due to C=N group , with shifted lower frequency at 1546 in complex, this indicates that C=N groups is participate in coordination to metal ions [10].New intensity band at 1608 cm -1 due to new C=N.New strong intensity band appears 1068cm -1 due to (C-O) group.(11) complex.In the IR spectrum of [Pd(L) 2 ] complex (11) showed weak band at 3197 cm -1 due to (N-H) group, and this was shifted to lower frequency, this indicates that N-H group is participate in coordination to metal ions.In the IR spectra of complex showed the one medium intensity band at 1600 cm -1 due to (C=N).One medium intensity band at 1660 cm -1 due to (C=O), with shifted to slightly lower frequencies compared with that of the ligand, this indicates that 2 C=O group is not participate in coordination to metal ion.

3-3. Conductivity measurements:
The molar conductance of these complexes 0.001 M in DMF at room temperature show that all the complexes are non-electrolytes [28].The value in the range 0.9-16.2cm 2 .ohm - .mol - table (3).According to these results the structural formula of prepared complexes may be proposed in (fig- 1).