Indian Journal of ChemistryVol. 26A, April 1987. pp. 341-344

Palladium(II) & Copper(II) Complexes ofSubstituted N-Thenylsalicylaldimines

C JOGINADHAM, U A BHAGWAT, V A MUKHEDKAR* &AJMUKHEDKAR

Received 17 March 1986; revised and accepted 3 October 1986

Pd(lJ) complexes of different substituted N-thenylsalicylal-dimines have been synthesised and characterised, The structuresproposed for these complexes and for the CU(lJ) complexes Cul.,and Cu2LzCl2 (L= N-thenylsalicylaldimine) are based on ele-mental analyses, infrared and IH NMR spectral data.

Reports on metal complexes of schiff bases derivedfrom 2-thenylamine and different aldehydes arescanty compared to reports on those derived fromthiophene- 2-carbaldehyde and different amines I. Inthe latter complexes, the thiophene sulphur is re-ported to selectively coordinate to metal ions. In theformer complexes, thiophene sulphur coordinationwas indicated? in some of the ligand isomeric com-plexes of N-thenylsalicylaldimine (L). This note re-ports the synthesis and characterisation of Pd(II) andCU(I1)complexes of substituted N-thenylsalicylaldi-mines.

Infrared spectra were recorded on Perkin-Elmer337 and Pye-U nicam PU 9512 spectrophotometers,IH NMR spectra were recorded on a Perkin-ElmerR-32 spectrometer. Elemental analyses were ob-tained from the microanalytical divisions of Uni-

versity Department of Chemistry, and NCL, Pune.The cryomagnetic measurements were performed inthe temperature range 85-300 K on a Faraday bal-ance and computations were done on an ICL 1904 Scomputer at Regional Computer Centre, Pune.

2-Thenylamine was synthesised by aminomethy-lation of thiophene'. o-Vanillin was obtained fromMis FLUKA chemicals. Other substituted salicy-laldehydes were synthesised using literature proce-dures", Other chemicals were of AR (BDH) grade.

All the Iigands (U-L7) (structure I) were synthe-

L: X = H; L': X = 5-Cl; L': X = 5-8r; U: X = 5-N02; U: X = 5,6-Benzo; LS:X= 3,5-Dibromo; L":X = 3,5-Dinitro; V: X = 3-0CH]

sised by refluxing the equimolar solutions of corre-sponding salicylaldehydes and 2-thenylamine. Thespectroscopic data of metal complexes are given inTable 1.

Synthesis of metal complexes (serial numbers ofcomplexes refer to those given in Table 1):

Table 1 - Physical Data for Metal Complexes'Sl.No. Complex Infrared spectra (ern - I) IH NMR spectra (ppm) IlB.M.

(300k)vC=N llCH2 vC-O vC-S-C llHC=N llNCH2

1 Pdli 1618 1445 1540 1320 8.20 5.102 Pd~ 1612 1438 1542 1312 8.15 4.953 PdW 1614 1450 1545 1315 8.22 4.904 PdL1 1618 1445 1541 1310 8.20 4.855 PdLi 1608 1442 1522 1278 8.15 5.20

1212 8.216 Pd~ 1602 1440 1526 1275 8.20 5.21

1340 8.357 Pdli 1614 1452 1528 1270 8.25 4.90

1345 8.358 Pd2LiCl2 1622 1455 1538 1280

13559 PdLz 1620 1448 1540 1320 8.25 5.2210 cot, 1615 1442 1542 1320 1.4611 Cu2LzClz 1617 1460 1540 1290 1.60

1342

'Important spectral bands for ligands; vC=N (infrared); L' -U, one band each in the region 1619-1635 cm-1.llCH (IH NMR):L' - U, one band each in the region 8.12-8.38 ppm.

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INDIAN J CHEM .. VOL. 26A. APRIL 1987

Complex (1 ):To a solution of U (4.72 g, 0.02 mol)in methanol (50 cm-) was added palladium(II) chlo-ride (1.79 g, 0.01 mol) in methanol and contentswere refluxed for 2 h. The resulting solution was re-duced in volume (in vacuo) and the residue so ob-tained was washed with methanol, acetone and die-thyl ether to afford yellow crystals of complex (1)(3.78 g, 65%).

Complexes (2 )-(4)were synthesised using a similarprocedure. For (5) and (6) also a similar procedurewas used except that the residue was recyrstallisedthrice from chloroform after washing with methanol.

Complexes (7) and(8): To a solution of L' (4.63 g,0.02 mol) in methanol (100 em") was added pow-dered palladium(II) chloride (1.79 g, 0.01 mol) andthe mixture was refluxed for 2 h. Then the volume ofthe solution was reduced in vacuo. The residue wascooled at O°Cfor 1h to get a sticky solid, which wasthoroughly washed with methanol and repeatedlyextracted from benzene. The residue was dried invacuo for several hours to get dark yellow crystals of(8). The benzene extract was evaporated under re-duced pressure when orange crystals of (7) (1.4 g,25%) were obtained.

Complexes (9) and (10) were synthesised using li-terature procedures",

Complex (11): To a suspension of complex (10)(2.48 g, 0.005 mol) in chloroform (100 em") wasadded copper(II) chloride (1.70 g, 0.01 mol) in etha-nol (100 em"). The mixture was refluxed for 8 h afterwhich a brown precipitate appeared. The volume ofthe solution was reduced in vacuo to get a sticky sol-id which on washing first with methanol and thenwith diethylether gave brown crystals of (11 ) (1.60 g,50%).

L is reported to exist in the isomeric formsSC4H3CH2N = CHPhOH-o and SC4H3CH =NCH2PhOH-o, which could be only separated astheir Pd(U) complexes-. However,the different sub-stituted ligands (U-U) did not exhibit such isomer-ism, as evident from the single peaks of N = CH pro-tons in the IH NMR spectra, and single bands due toC = N stretching frequencies in the LR spectra.

Pd(II) complexes of ligands U-L7 were synthe-sised. Complex (1) was insoluble in common sol-vents like chloroform but could be brought into so-lution using solvents which behaved as lewis bases,such as pyridine. The IH NMR spectrum of (1) (de-termined in [2HsJ-pyridine) gave two sharp signals at6 8.20 and 5.10 ppm for N = CH and N - CH2 pro-tons respectively. Similarly two sharp singlets wereobserved in the IH NMR spectra of complexes (2)-(4), which showed solubility behaviour similar tothat of (1 ).Complexes (5H7) were soluble in chloro-form. Two bands of unequal intensity appeared at

342

8.15 and 8.21 ppm, for the azomethine proton in theIH NMR spectrum of (5) (determined in CDCI3)

suggesting an equilibrium between square planar (A)and octahedral (B) configurations in solution. Simi-lar to (5), IH NMR spectra of (6) and (7) displayedtwo azomethine signals in addition to the one forN - CH2 group. The IH NMR spectrum of (8) couldnot be determined due to its solubility limitations; itwas insoluble in common solvents and efforts to dis-solve it in pyridine or dimethyl sulphoxide resultedin the decomposition of the complex.

(A) (8)

Complexes synthesised in the present workshowed vC = N in the region 1602-1622 cm - 1. Amedium intensity band appearing at 1522 em - I inthe IR spectrum of (5) was assigned to C - 0 (phen-olic) stretching vibration'. These bands for com-plexes (6) and (7) were observed at 1526 and 1528em - I and those for (1)-(4 ) were in the region 1540-1545 cm-I. A band in the region 1270-1350 cm-I isassigned? to the vC - S - C (thiophene ring) vibra-tion in the infrared spectra of metal complexes of L.The infrared spectra of complexes (1)-(4) showedone band each in this region whereas two bands ap-peared for complexes (5)-(8) indicating the probablecoordination of heteroatom to metal.

The elemental analyses data suggested generalformula PdU Z for complexes (1 )-(7) and PdzI..JC12for (8). The lower solubilities and higher phenolicC - 0 stretching frequencies of complexes (1 )-(4 )compared to those of (5)-(7) suggested a binuclearconfiguration (C)6 for (1 H4).The thiophene sulphur

(e)

NOTES

Table 2 - Analytical Data of Complexes" (1)-(11)

Complex m.p.(°C) Found (Calc.), %

C H M ClorBr

(1) 180-2(d) 47.12 2.85 17.90 11.90(47.42) (2.96) (17.52) (11.69)

(2) 21O(d) 41.72 2.82 15.02 22.72(41.35) (2.58) (15.28) (22.98)

(3) 232-4(d) 45.32 2.85 16.82(45.83) (2.86) (16.93)

(4) 192 60.05 3.69 16.60(60.15) (3.76) (16.67)

(5) 160-4(d) 34.15 1.95 12.30 37.42(33.70) (1.87) (12.45) (37.45)

(6) 146 40.32 2.30 14.42(40.08) (2.23) (14.81)

(7) 162 51.90 4.45 17.62(52.13) (4.01") (17.78)

(8) 180(d) 40.50 2.92 29.60 10.21(40.23) (2.79) (29.72) (9.92)

(9) 190-2(d) 53.82 3.90 19.52(53.49) (3.71) (19.76)

(10) 220-3(d) 58.60 4.35 12.60(58.12) (4.04) (12.82)

(Il) 180(d) 50.95 3.90 1l.62 12.58(50.83) (3.53) (11.20) (12.53)

"All the ligands gave satisfactory elemental analyses; Ligands V - U are solids showing sharp melting points.

coordination was absent in these complexes prob-ably due to their coordinative saturation.

Complex (11) was synthesised using (10) as com-plex ligand. The infrared spectrum of this complexgave one band each for vC = Nand vC - 0 and twobands for vC - S - C. Its elemental analysis data sug-gested the molecular formula to be Cu2LzCl2• Astructure similar to that of (8) (0)5 is suggested for

(0)

(11) on the basis of these data. The room tempera-ture magnetic moment of complex(IL) was found tobe 1.6 B.M. A plot of inverse molar magnetic sus-ceptibility vs temperature is given in Fig. 1. Thecomputer fitting of Bleany-Bower's equation? (eq.1),

N 2{32 3e2J/kT

x =-g- +N (1)M 3kT' 1 + 3e2J/kT a ...

1100.000

1080

~

00

&00 2o

r»: t.¥ 700 \D~

.a. 1060~

~o: ,040

:>:><

1020.

60C "

IOOOO.L-,---:,,:-O -"--:'0::-'---+"20 160 2~-· J ·-Uo-~- sco

1/.

Fig. 1 - Plot of inverse molar magnetic susceptibility versustemperature for complexes 10 (-e-) and 11 (-0-)

where Nis the Avogadro number, {3,the Bohr mag-neton, k, the boltzman constant and N, the tempera-ture-independent magnetic susceptibility assumedto be 60 x 10-6 C g s units gave the values: g, 2.1(± 0.03); and J, -160 cm-1 (± 10 em-I). These va-lues are comparable to those found for the binuclearcomplexes of the complex ligand bis-(N-alkylsalicy-laid imino )copper(II) (alkyl = methyl, see-butyl)".

The authors thank the Head, Department ofChemistry, University of Poona for providing neces-sary facilities and to Mrs. R.Y. Kashalkar for helpful

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INDIAN J CHEM., VOL. 26A, APRIL 1987

assistance. One of them (CJ.) thanks the CSIR, NewDelhi for a senior research fellowship.

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Coakley M P, Young L H & Grallagher R A, J inorg nuclChern, 31 (1969) 1449; Motobe H K & Yamada S, BullchemSocJapan, 51 (1978) 2429.

2 Mukhedkar V A, Bhagwat U A & Mukhedkar AJ, J chem Soc,Dalton Trans, (1982) 1899.

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(1966) 83.7 Bleany B & Bowers K D, Proc R Soc London Ser A, A214

(1952) 451.8 Harris C M & Sinn E, J inorg nucl Chem, 30 (1968) 2723.