Synthesis and characterization of nickel(II), copper(II ...nopr.niscair.res.in/bitstream/123456789/40948/1/IJC 33A(7) 638-643.pdf · framework incorporating more than one metal ion.

Indian Journal of ChemistryVol. 33A, J1l1y1994, pp. 638-643

Synthesis and characterization of nickel(II), copper(II), palladium(II) andplatinum(II and IV) complexes with azolo 2,4-pentanedione-Part Il!

Lallan Mishra* & Anjali JhaDepartment of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221 OU5

Received 7 October 1993; revised 13 December 1993; rerevised 14 January 1994 accepted 2 February 1994

The dinuclear Pd(JJ) and Pt(II) and polynuclear Ni(II), CufH), Pt(IV) compeJxes with substituted pro-ducts of2, 4-pentanedione (azolo 2, 4-pentanedione) have been prepared and characterized on the basis ofelemental analyses, conductance, magnetic and IR, UV/VIS, NMR and ESR spectral studies.

The azolo diazonium saIts coupled with 2, 4-pentane-dione have been reported as an intermediate in thesynthesis of antimicrobial asymmetrical triazines ':Additionally, such B-diketones could be exploited asdinucleating ligands, since they possess two coordi-nation sites, one in heterocyclic ring and other in thediketone. Furthermore, the physiological activityand commercial application of benzimidazole deri-vative, especially-z-aminobenzirnidazole have recei-ved much attention". Thus the above report and ourcontinued search for the new dinucleating ligandsand their dinuclear/polynuclear complexes+" promp-ted us to condense the azolo pentanedione (L') with I,6/1, 8-diamino hexane/octane in the presence of me-tal salts. The choice of the amines was based on ourprevious reports which provide flexible macrocyclic"framework incorporating more than one metal ion.

u,' )Materials and Methods

All the solvents used in this study were distilledprior to use. 2, 4-Pentanedione, I, 6-diaminohexane,1, 8-diaminooctane and all the metal salts were pur-chased from SD Fine Chemical Co. and used withoutany further purification.

Synthesis of ligandThe substituted 2. 4-oentanedione was prepared

tPart I: Transition Met Chem. 18 (1993) 559.

by the literature method I by, diazotizing the 2-amino-5-chlorobenzimidazole (5 mmol) and then reactingwith 2, 4-pentanedione (5 mmol) in distilled water (25ml). The resulting product was filtered and washedseveral times with water and then ethanol. The crudeproduct was recrystallized with water-ethanol (1:I,v/v) mixture, yield 55-60%.

Preparation of metal complexesThe general procedure adopted for the preparation

of metal complexes is as follows. An ethanolic (10 ml)solution of the respective amine (I mmol) was added toan ethanolic solution (10 ml) of substituted 2, 4-pent-anedione (L') (1 mmol) with constant stirring. To theclear solution thus obtained, ethanolic solution (10ml) of the respective metal salts (2 mmol) was addedgradually while stirring, followed by the addition of2-3 drops of triethylamine. The contents were reflux-ed for 3-4 h and then kept in the refrigerator over-night. A crystalline substance thus obtained was filte-red and washed with ethanol followed by ether anddried in vacuo.

The ligand displacement study was made by de-complexing one of the complex [Cu2(LI)CI3(H20)](Table I) using the reported method". Hydrogen sul-phide gas was passed very slowly through a DMSOsolution (20 ml) of the complex (40 mg) with stirringfor 3 h. After filtration, a large excess of sodium hyd-rogen carbonate was added to the yellow filtrate,which was stirred vigorously for 2 h in an inert atmos-phere. The mixture was filtered and the filtrate con-centrated to dryness under reduced pressure. Themass thus obtained was dissolved in pet. ether(60-80T). The pet. ether insoluble part was identifiedas copper(II) complex, while the soluble part was fur-ther concentrated up to dryness and the sticky massobtained gave iu]« = 364 containing closed macrocy-

MISHRA et af.: STUDIES ON Ni(II), Cu(II),Pd(Il) & Pt(lI, IV) COMPLEXES 639

Table I-Analytical data of the ligand and metal complexes

SI No. Compound Colour Found (Calc.), % Magnetic(m.p.,°C) moment

C H N M CI ~ff. (B.M.)

L' Yellow 52.5 4.0 20.5 12.1

(182-185) (51.7) (3.9) (20.1) (12.7)

2 [Ni2(L,)*(CH)COO»)(H2Oh] Brown 42.5 5.8 12.6 17.9 5.3 5.93

(> 250) (41.8) (5.0) (12.2) (17.0) (5.1)

3 [NiiL,)CllH2Ohl Brown 34.5 5.1 13.5 19.8 21.9 5.95

(> 250) (33.9) (4.4) (13.2) (18.4) (22.3)

4 [Cu2(L,)(CH)COO)3(H2O)1 Brown 41.7 5.3 12.7 19.8 5.8 2.28

(> 250) (42.3) (4.8) (12.3) (18.6) (5.2)

5 [Cu2(L1)CI)(H2O) Brown 35.8 4.2 13.4 21.0 23.7 2.08

(> 250) (34.4) (3.9) (13.7) (20.8) (23.3)

6 [Pdz(LdCl)(H20)] Brown 32.2 4.0 12.3 31.2 19.8 Diamagnetic

(> 250) (31.0) (3.4) (12.0) (30.6) (20.4)

7 [Pt11~LI)CI3(H20)] Brown 25.0 3.2 8.9 16.7 Diamagnetic

(> 250) (24.7) (2.7) (8.6) (44.7) (16.2)

8 [Pdv(L1)CI7] Brown 22.0 2.9 8.8 28.0 Diamagnetic

(> 250) (21.6) (2.2) (8.4) (39.1) (28.5)

9 [Ni2( L2)*CI J(H 20 hl Brown 36.9 5.0 12.8 18.0 21.9 5.45

(>250) (36.1) (4.8) (12.6) (17.6) (21.4)

\0 [Cuz(L2)Cl)(H20)] Brown 36.4 4.0 13.6 20.6 22.0 2.51

l> 250) (37.6) (4.3) (13.1 ) (19.9) (22.2)

*L, & Lz corresponds to ligand L' with I, 6-diaminohexane and I, 8-diaminooctane respectively.

c1e(m/e ~ 358) with a little fraction of pet. ether. TheIH NM R spectra (in COCI3) of this compound sho-wed peaks at (0 ppm) 7.23 (aromatic protons), 5.20(NH), 2.56 (N-CH2), 2.13 (4 CH2) and 1.23 (2 CH3)'The high intensity of aromatic protons may be due topet. ether. Thus the spectra of the sticky mass wasindicative of the presence of the ligand (Structure I).The sticky nature of the material precluded its furtherstudy.

I. Structure of closed macrocycle

The metal (except Pt) and chloride in the complexeswere estimated following standard procedure 7• Car-bon, hydrogen and nitrogen were analyzed at theCORI, Lucknow. The magnetic susceptibilities weremeasured on a Cahn Faraday electrobalance usingHg[CO(NCS)4J as the calibrant. The diamagnetic cor-rections were applied using Pascal's constants", TheIR spectra (4000-400 em - I region) in KBr pellets and

Uv/visible spectra (in nujol mull and in acetic acid)were recorded on Jasco FTjIR-5300 and Cary-23spectrophotometers respectively. The IH NMR spe-ctra were recorded [in DMSO-d6J on a Jeol FX-90 Qspectrophotometer using TMS as an internal referen-ce. The ESR spectra of the copper complexes in solidas well as in solution (acetic acid) were recorded on aVarian X-band spectrometer E-4 at RSIC, lIT, Bo-mbay. The molar conductances were measured on aScientronic digital conductivity bridge at a concen-tration of '" 10- 3 M in OMSO. The analytical dataare presented in Table I.

Results and DiscussionAll the complexes were found to be stable in solid

state. They showed non-electrolytic behaviour inDMSO. The empirical composition of the complexesalongwith their physical data are given in Table I. Thecomplexes are relatively less soluble in common sol-vents except in OMSO and acetic acid.

In the IR spectra of 2, 4-pentanedione bearing 2-amino-5-chlorobenzimidazole ring (L'), major pe-aksobserved at3314, 3088, 1691, 1547and 1413cm-'were assigned to vNH, vCH (of aromatic), v> C=O,vC= N, (of the ring) and vN = N respectively whereasthe complexes showed major peaks at 3422, 1631,

640 INDIAN J CHEM, SEe. A, JULY 1994

(c )

--~~.-.....-~~""---~~",,,~,,--,--~~\ t gz

Cd) v>, \/\:

2000G

f gx

t !IXgy n MARKER (TCME)

gy ~

I) MARKER (TCME)

II

~

200G~

II

~}VtI I I I I I I I I I I I

-0.5 0.4 -0.3 -0.2 -0.1 0 0.1 0.2I I I I

0.3 0.4 0.5

Fig. I-Powder ESR spectra of (c) [Cu2(LI)C13(H20)J and (d)[Cuz(L2)C13(HzO)] at Liquid Nitrogen Temperature.

1550 and 1402 em -I. Thus the disappearance of theparen t peak '" 1691 em - 1 indicated that> C = 0group of the parent compound (L') is condensed withthe diamine", and a peak lying at '" 1631cm -I is assig-ned to delocalized vC = N'O vibrations. Furthermo-re, the lowering of the peak due to vC = N group (ofthe ring) and - N = N - indicated the coordinationof> C= N grouptof the ring) and - N = N - presentin the parent ligand (L'). The bidentate coordinationof acetate groups is reflected in the complexes 2, 4(Table I), the presence of broader peaks centered at'" 1574 and '" 1422 cm -1 assumed as Vasym

CH3COO - and vsym CH3COO - respectively in view ofearlier report 1I. But in Cu(IJ) acetate complexes, oneof the CH3COO group is considered as monodentatein view of the coordination requirement and couldnot be distinguished owing to the poor resolutions ofthe spectra. Furthermore, the poor resolution of thespectra again prevented us from assigning vM - N,vM - 0 and vM - Cl vibrations, since ligand peaksobserved in this region overlapped with the peaks inthe complexes.

F or further support of the coordination of ligand(L') with metals, its solution 'HNMR spectra wascompared with that of soluble complexes of Ni(II).The NMR spectra of(L') showed peaks at 0 8.90, 7.13to 6.90, 6.59 and 1.95 ppm assigned to OH, phenyl,NH and CH3 protons respectively. The presence ofOH protons showed that ligand exists in enol form inthe solution. The nickel(II) chloride complex of lig-and (Lj ) showed the broader peaks centered at 0 6.8,

2.8, 1.66 and 1.33 ppm assigned to NH, (N - CH2h,2(CH3) protons and (4 CH2) protons from amine res-pectively. The intensity of the peaks correspond wellto the number of protons, which support the forma-tion of a cyclic product. The poor solubility of theremaining complexes prevented us from recordingtheir NMR spectra.

The room temperature solid state magnetic data ofthe complexes are reported in Table 1. The Ni(II)complexes showed normal magnetic moments consi-stent with the earlier reports 12. However, Cu(JI) com-plexes showed lower magnetic moment than expectedfor normal octahedral complexes indicating signific-ant interaction between Cu(IJ) ions. The Pt(lI) andPd(IJ) complexes were found to be diamagneticwhich indicated the square planar geometry, whereasPt(lV) complex was also found diamagnetic but anoctahedral geometry was assigned".

the electronic spectral data of the ligand and com-plexes recorded in solid and in solution (acetic acid)are shown in Table 2. The spectral feature of Ni(JI)complexes were found to be similar to those of repor-ted octahedral Ni(IJ) complexes 13. The Cu(IJ) comp-lexes showed bands in 640-670 nm range which wereassigned to d-dtransitions2. The solution spectra de-picted broader bands. The same spectra when recor-ded in more inductive CICH2COOH causes a prono-unced shift towards higher Amax value (Table 2) whichis consistent with the earlier report!" where the axialsubstituted band is found to be sensitive to both thenature and inductive effect of the substituent. A blue

MISHRA et al.: STUDIES ON Ni(Il), Cu(I1),Pd(Il} & Pt(ll, IV) COMPLEXES 641

Table 2-Electronic spectral data of the ligand (L') and complexes

SI No. Compound Solid A.m.,(em) Solution "m",.(nm) [tEma,M - I em -IIAcetic acid Chloro acetic Trichloro acetic

acid acid

L' 380, 420, 480 380, 430, 480,[400] [250] [360]

2 [Ni2(LI )(CH)COOh(H2O») 290, 470, 490, 280, 340, 440,640, 880, 970 [700] [700] [360],

580, 720 (b)*,[150] [100]

3 [Ni2(LI )CliH2Oh] 400, 476, 502, 340, 425, 445,634,654 [900] [850] [780],

640,660, 755 (b)*,[240] [200] [120]

4 [Cuz(L1)(CH)COOh(HzO») 400, 530, 650, 430, 460, 660 (b), 450, 540, 640, 460, 545, 665,[300] [260] [880] [580) [400] [350], [350] [210] [270],

750 (b), 780 (b),[320] [320]

5 [Cuz(L1)CI)(H2O)] 460, 490, 640, 665 400, 460, 480, 450, 500, 650, 480, 520, 650,[860] [750) [660), [550) [300] (l00], [330) [200] [160),675 (b) 780 (b) 715, 780 (b)(780) [380) [280) [380)

6 [Pd2(L1)CI)(H2O») 240, 300, 400, 4807 [Pt~I(LI)CI)(H20») 240, 300, 410, 4808 [Pdv(L1)CI7] 260, 300, 370, 4609 [Ni2(Lz)CI)(H2O)] 450, 495, 640, 660 335, 440, 580,

(WOO) [380) [170)660, 700 (b)[100](50]

10 [Cuz(L2)CI)(HzO») 465, 495, 640, 665 440,465, 680 (b) 455, 550, 680 460, 555, 670,[470) [420) [570] [580) [400] [350) (350) [260] [200]

750 (b) 780 (b)[320) [200]

*(b)Indicates broader peak.+elndicates extinction coefficient.

Table 3-ESR parameters of Cu(II) complexes

SI Complexes StateNo. (temp.)

[Cuz(L1)CI)(HzO)] Powder(RT)(LNT)

2 [Cuz(L1)CI)(H2O») Solution(LNT)

.J [Cuz(L1)CI)(HzO)] Powder(RT)(LNT)

4 [Cu2(LI )CI3(H2O») Solution(LNT)

g values A (63.65CU)values (G)

gz gy g, All A,L Az At Aty r:

2.275 2.201 1.985 160 20 13.32.291 2.028 1.971 140 20 20

140 25

2.290 2.027 1.979 140 20 202.298 2.035 1.984 160 20 26

140' 35a

(80)b

2.373 2.122

2.356a* 2.04la(1.907)b* (2.002)b

+Since in (x, y) region (63.65CU)splitting is not observed therefore Ay and A, is taken as 1/3 of the peak width observed in this region.*a and b represented two coordinating sites of the ligand.

642 INDIAN J CHEM, SEe. A, JULY 1994

2000G

t

I I

-0.5 -0.4I I I I I I I , I I , , I I , I

-0.3 -0.2 -0.1 o 0.1 fJ.2 0.3 0.4 0.5

Fig. 2-Solution (acetic acid) ESR spectra of (c) [CuiL,)CllH20)]and (d) [Cu2(L2)C13(H20)] at Liquid Nitrogen Temperature

shift of the charge transfer bands for the complexes inthe solution state spectra as compared to their solidstate spectra also indicates that the complexes adopt anew geometry perhaps by the participation of solventin coordination. Further, this inference is substantia-ted by ESR spectra in the same solvent (acetic acid).

The ESR spectral data ofCu(II) complexes in pow-der at room temperature and liquid nitrogen tempe.rature as well as in solution at LNT only are given inTable 3. The spectra (Figs I and 2) are consistent withthe four equally spaced lines as expected for Cu(II)ions. However, the splitting in the perpendicular reg-ion is not observed. The powder spectra at LNT (Fig.I) display anisotropic effect whereas frozen solutionspectra (Fig. 2) display gll and g.i values such asgll> g.i which are consistent with a tetragonally elon-gated structure'>. Additionally, the parallel region ofthe spectra (Fig. 2c) gave five signals due to the splitt-ing caused by 14N nuclei, showing the presence of twonitrogens lying around Cu(II) ions at 10 G for All(14N). Furthermore, the spectral pattern shown inFig. 2 indicated that Cu(II) ions arc lying in two differ-ent environments [closed and open coordination sitesof the ligand represented as region a and b].

Thus, on the basis of the above elemental analyses,spectral and magnetic properties alongwith our pre-vious reports", the tentative structures for these com-

o plexes could be depicted as shown (Structure II).

, ., .'c;;.1'\x : x Hz"/ CH, C

x-Cu { /o~ ,.x,CI , , .,._N..J>~ "', ,/

N N I t:u- ----~Jl.-I/ "'~/ -·.~Hz~,'C'l"VN' N " /', , •

I CH, C XH Hz

For" .4, X. ICH,COO) ICI, n • 6. X. CIlb)

tl CI H\.Ii=' ,........CZ

CI /\ .,_N, •..~'(!r-.l./ ~,-...:."1oI'C.)CHZ)4

~I CH, <;»HI

For 101.Pdlll) and Pt Ill)(d)

tHJII. Proposed structure of metal complexes

MISHRA et al.:STUDIES ON Ni{II), Cu{II),Pd{II) & Pt{II, IV) COMPlEXES 643

ACknowledgementThe authors are thankful to the Ministry of Envi-

ronment, New Delhi, forproviding financial assista-nce.

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1357.7 Vogel A I, A text book of quantitative inorganic analyses (ELBS

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