INDIAN J. CHEM., VOL. 21A, MAY 1982

RETA

~H (I/ ~/ HIo co) VI'r\ "0 OH.

HzONi compte.

co (t I) compie.

Cu (II) compte.

monobasic tridentate with the alcoholic oxygencoordinating without! deprotonation" whereas inother chelates it is acting as a dibasic tridentate

The magnetic moment of (5.14 B.M.) for.Co(I1)complex isfairly higher than the reported SPIll-Onlyvalue. The electronic bands at 15600 and 20000 anda weak band at 12900 are more in consistence withtriagonal bipyramidal geometry than octahedral orplanar disposition'>, The bands at 15600 and20000 can be assigned respectively to 4A'2 (P) +---~A '2(F) and 4E"(P) +--- 4A '2(F) transitions's. Theobserved magnetic moment value (3.45 B.M.) forNi(II) complex shows no probability of squareplanar or octahedral geometry'". Hence, it is pro-posed that the complex has tetrahedral dispositionwhich is supported by electronic spectral band at15380 assignable to 3T1(P) ~- 3T1(F) transition+,The probable structures of the complexes are givenin Fig. 1.

The authors are thankful to Prof. M. M. TaquiKhan, Head, Department of Chemistry, O.sm~niaUniversity and Prof. V. R. Srinivasan, Principal,Osmania University Science College for providingfacilities. One of the authors (VA) is grateful tothe CSIR, New Delhi for the award of a researchfellowship.

References

1. PODDAR, S. N., DEY, K., HALDAR, J. & NATHSARKAR.,J. Indian Chem. Soc., 47 (1910),143.

2. YAMADA,S., KUGE, Y. & YAMANOUCHl., Bull. chem. Soc.Japan., 40 (1967), 1864.

3. SINGH, H. & TANDON, J. P., Indian J. Chem., 17 A (1979),620.

4. SYAMAL, A. & KALE, K. S., Indian J. Chem., 19A (1980),486.

S. G~ERLEU, N. V., Ser. Biol=i-Khim. Nauk., 11 (1964),3; Chem. Abstr .• 64 (1964), 9220.

6. HANS ZIMMER., BENJAMIN GROSS H., HUGH GERLACH, E.,-KENNETH FRY, ANDREW PRONAY, C. & HORST SCHMANK.,J. org. Chem., 24 (1969), 1969. .

7. VOGEL, A. I., Quantitative inorganic analysis (Longmans,London) 1968.

8 COLTHOP N. B., DALY, L. H. & WIBERLY, S. E., Introduction. to infrdred and Raman spectroscopy (London, Academic

Press), 1964, 274, 380.

534

9. SRIVASTAVA,T. N., CHAUHAN, A. K. S. & DIWEDI, IndianJ. Chern., 19A (1980) 269.

10. LEVER, A. B. P., Inorganic electronic spectroscopy (Elsevier,London), 1968, 356.

11. SUlTON, D., Electronic spectra of transition metal complexes(McGraw-HilI, New York), 1968, 146, 188.

12. CrAMPOLlNI, M. & SPERONI, G. P. S., Inorg, Chem .• 5 (1966),45.

13. Corrox, F. A. & WILKINSON G., Advanced inorganic che-mistry (John Wiley and Sons), 1969,883.

Dioxomolybdenum (VI) Complexes of Schiff BasesDerived from Salicylaldehyde, Substituted Salicylal-

dehydes & Beozoylhydrazide

A. SYAMAL* & D. KUMARDepartment of Applied Sciences and Humanities, KurukshetraUniversity, Kurukshetra 132119, and Department of Chemistry,

Regional Engineering College, Kurukshetra 132119

Received 14 September 1981; revised and accepted 5 November1981

Several new dioxomolybdenum(VI) complexes of sdillf basesderived !rom salicylaldehyde. 5-ch1orosaUcyIaldehyde. 5-bromo-salicylaldehyde. 5-nitrosalicylaldehyde. 2-bydroxy-l-naphtbal-debyde and benzoylhydrazide have been syntbesised and characteraed by elemental analyses, quantitative determination ofligand, m, conductance, molecular weight and magnetic suscep-tibility measurements. The ligands behave as ONO donordibasic tridentates and form complexes of the type MoO.L.H.O(where LH.=schifI' base). These complexes react with tetra-hYdrofuran (THF) to give the adducts, MoO.L.TIIF. All thecomplexes are monomers, non-electrolytes and diamagnetic. TheTHF adducts are less stable than the aquo adducts. IR datandicate that the complexes possess cis-MoO. structure.

MOLYBDENUM is coordinated to nitrogen,oxygen and/or sulphur atoms in enzymes like

nitrogenase, aldehyde oxidase, xanthine oxidase,sulphite oxidase, nitrate reductase and xanthine dehy-drogenase-. The valence of molybdenum varies de-pending on the nature of the enzyme, and the functionof some redox enzymes is dependent on variablevalence molybdenum cofactors. In order to under-stand the gross mechanism of enzyme activity, experi-ments on relatively small molecules are needed. Wereport here the synthesis of some model molybdenumcoordination complexes of the type(I) with thedianions of tridentate ONO donor schiff bases(II)derived from benzoylhydrazide and salicylaldehydeor substituted salicylaldehyde and monodentateoxygen donor neutral ligand (X) like H20 or tetra-hydrofuran (THF). Not much work seems to have

o(o,Jl~oNC[>

x1 x= H20,THF U. X=H. 5-Chloro, 5-Bromo, 5-Nit ro,

5,&-Banzo

NOTES

been reported on dioxomolybdenum(VI) complexesof tridentate Iigands".

All the chemicals, viz. salicylaldehyde, ammoniummolybdate (Sarabhai-Merck); 3,5-dichlorosalicylal-dehyde, 5-nitrosalicylaldehydt: (Eastman Kodak);3-ethoxysalicylaldehyde, 5-chlorosalicylaldehyde, 5-bromo salicylaldehyde (Aldrich Chemicals); and 2-hydroxyl-1-naphthaldehyde, and 3-methoxysalicylal-dehyde (Fluka AG) were of acceptable grades ofpurity. Benzoylhydrazide", salicylhydrazide" and theschiff basest were prepared according to the methodsdescribed elsewhere.

Syntheses of complexes: Mo02L.H20 - A solutionof appropriate schiff base (0.001 mol) in methanol(20 ml) was added to a solution of ammonium moly-bdate (1.23g, 0.001 mol) in 0.1 N sulphuric acid(30 ml). This was stirred for 30 min, heated on awater-bath for 30 min and the orange red precipitatethus formed filtered, washed with hot water, etherand dried in vacuo at room temperature, yield 60%.

M002L.THF - Tetrahydrofuran (20 ml) was addedto Mo02L.H20 (0.001 mol) and the mixture refluxedon a water-bath for 2 hr. The reaction mixture wasconcentrated to about 5 ml and the separated yellowcompound obtained was filtered, washed with THFand recrystallized from THF. The complexes weredried in vacuo at room temperature, yield 40%.

The ligands in the complexes were estimated asfollows: The complex ( '" 0.1 g) was boiled with asolution of 0.1 N NaOH (50 ml) for Ihr and filtered.To the filtrate was added a solution of 0.1 N KBrOa-O.lN KBr (40 ml) followed by 2.5 N HCI (50 ml).The mixture was shaken for 2 hr at room temperatureand titrated against standard sodium thiosulphatesolution to the starch end point iodometrically.Molybdenum in the complexes was determined by

decomposing the complex with cone. HNOa, ignitingand weighing as Moo, (Table I).

New dioxomolybdenum(VI) complexes of the typeMo02L.H20 are orange red, insoluble in water andsoluble in methanol, ethanol, dioxane, THF, dimethyl-foramamide (DMF) and dimethyl sulphoxide(DMSO). The yellow complexes of the type Mo02L.THF (where LH2 = Schiff base) are soluble inmethanol, ethanol, dioxane, THF, DMF andDMSO.

The schiff bases react with the acidic solution ofammonium molybdate to give complexes of the typeMo02L.H20. The labile H20 molecule in thesecomplexes is easily replaced by THF resulting incomplexes of the type Mo02.L.THF. The presenceof a medium intense broad band at ",3300 cm-1in the IR spectra of Mo02L.H20 has been assignedto ,,(OH) of coordinated water. This band is absentin Mo02L.THF. The bands due to "as (C-O-C) and". (C-·O-C) of coordinated THF is seen to occur atlower wave number (6" = 59-69 and 49-69 crrr?respectively) in comparison to the corresponding freeTHF at 1069 and 909 cm=' respectively", indicatingthe presence of coordinated THF molecule. Thecomplexes Mo02L.H20 do not decompose or loseweight on heating at 120°C for several hours, suppor-ting the coordinated nature of water molecule. How-ever, the THF adducts decompose as well as loseweight at 120°C, indicating lesser stability of THFadducts as compared to aquo adducts.

The infrared spectra of the complexes exhibitbands in the region 900-920 and 940-945 cm-!assignable to "as (O=Mo=O) and "B(O=Mo=O)respectively, the first one being a split band except inMo02 (5-nitrosal-BHZ)H20. In the complex Mo02(hydrox-BHZ). THF these bands cannot be assigned

TABLE 1 - ANALYTICAL AND MOLECULAR WEIGHT DATA OF DIOXOMOLYBDENlJM(Vn CoMPLEXfS

Found (Calc.), % Mol. wt, foundComplex- ,---- (calc)

Mo N Ligand

MoO,(sal-BHZ).H2O 25.1 7.0 61.6 3,)3C"H"N,O&Mo (25.00) (7.29) (61.9S) (3S4)

MoO,(5-chlorosal-BHZ).H2O 22.9 6.S 65.4 402C,.HllN,O&CI Mo (22.94) (6.69) (65.11) (418.5)

MoO,(5-bromosal-BHZ).H.O 20.9 6.3 68.2 451C"HllN.OtBr Mo nO.73) (6.05) (6S.47) (463)

MoO.(5-nitrosal-BHZ).H2O 2"..2 9.S 65.7 448C14HllN,O,Mo (22.38) (9.79) (65.97) (429)

MoO,(hydrox-BHZ).H.O 22.1 6.5 66.6 417C1sH"N,.O&Mo (22.12) (6.45) (66.36) (434)

MoO,(sal-BHZ).THFb 21.7 6.1 70.5 455C1.H18N.O.Mo (21.92) (6.39) (70.7S) (43S)

MoO,(5-chlorosal-BHZ). THFb 20.5 5.7 71.6 490ClIH17N.O&CIM(\ (20.32) (5.93) (72.91) (4n.5)

MoO,(5-bromosal-BHZ). THFb 18.5 5.2 75.9 535C18H'7N20.BrMo (18.57) (5.42) (75.24) (517)

MoO 2(nitrosal- BHZ). THFb 19.6 8.5 74.2 572CJ8H17N207Mo (19.88) (S.67) (73.49) (483)

MoO.(hydrox-BHZ).THFb 19.5 6.0 73.2 502C.,H ••N.O.Mo (19.67) (5.74) (73.7/) (488)

(a) Abbreviations : BHZ=benzoylhydrazide, sal = salicylaldehyde, 5-chlorosal = 5-chlorosalicyla.ldehyde, 5-bro-mosal = 5-bromosalicylaldehyde, 5nitrosal = 5-nitrosalicylaldehyde and hydrox=2-hycroxy-I-naphthaldehyde.

(b) Ligand % = (Schiff base and THF) %.

535

INDIAN J. CHEM •• VOL. 21A. MAY 1982

as the bands are masked by the absorption of schiffbase. The IR data indicate the O:=Mo=O species.to be cis as the trans 0= Mo= 0 species would showone Vas (O=Mo=O) band in this region=", the,vs(O=Mo=O) being IR inactive. Theory predictsthat in the cis complex the v. (O=Mo=O) wouldoccur at higher energy than that of Vas (O=Mo=O)and these bands have been assigned accordingly.The tendency of MoO~+ to form a cis configurationis due to double bonding between Mo and two oxygenatoms. The splitting of the Va. band by about 10 cm-1

may result from the crystal packing effect. No bandcould be assigned to lower frequencies ( < 850 cnr-')due to Mo-O-Mo bridge which is known to absorbat lower frequency region. The force constant valuesfor Mo= 0 bond are in the range 7.20-7.27 mdynesjA and agree well with those reported in theliterature'". The replacement of H20 by THF doesnot produce significant effect on the v(O=Mo=O).The electronic effect of the substituents in the benzenering is also not significant on the v(O=Mo=O)of the complexes.

The schiff bases exhibit the v(C= 0) at 1635-1668 cm-I. In the complexes this band is absent,indicating the destruction of C=O group because ofenolisations, The complexes exhibit a new band inthe region 1210-1260 cm-l due to v(C-O) (enolie).The V (C = N) band occurring at 1995-1620 cm-lin the ligands shifts to lower energy by 5-15 cm-lindicating coordination of ligands through the nitro-gen atoms-'. The v(C-O) (phenolic) of the ligands at1515-1545 cm+' shifts to higher wave numbersuggesting coordination of the schiff bases throughoxygen atoms". The IR data indicate tridentate,ONO donor behaviour of the Iigands. Thus, thecomplexes are straight forward six-coordinated.

The complexes behave as non-electrolytes (Ax=. 0.2-4.5 ohm-! em" mol-l) in THF. Their molecularweights determined by Rast's method in diphenylindicate these to be monomers. All the complexesarediamagnatic as expected for a Ad" system.

The authors are indebted to the Department ofScience and Technology, Government of India forfinancial .support for this work.

References\

1. BRAY, R. C., Enzymes.,IZ (1975), 299; WENTWORTH,R.A~ D., Coord. chem. Rev .• 18 (1776), 1; Stiefel, E. I.,Progri-inorg, Chem .• 2l (1977), 1.

2. RAJAN, O. A. & CHAKRAVORTY,A., Inorg: chim, Acta.37 (1979), LS03; PODDAR,S. N.• GHOSH,S. & SAMANTA,G.· C., J. Indian chem. Soc .• 57 (1980), 92; TOPICH,J. Inorg. chim, Acta, 46 (1980), L37.

3. GAT1'ER.ldAN,L. & WIELAND, H., Laboratory methods oforganic chemistry (McMillan, London), 1963, 153.

4. KACHHAWAHA,M. S. & BHATIACHARYA,A. K., J. inorg.nucl. Chem., 2S (1963), 361. .

S. SYAMAL,A. & KALE, K. S.• Indian J. Chem .• 16A (1978),46.

6. MANN, F. G. & SAUNDERS,B. C., Practical organicchemistry (Longmans, London), 1961. 435.

7. BELLAMY~. L. J., The infrared spectra of complex mole-cules (John Wiley, New York), 1958, 119.

8. GOFFART,J., MEVNlER, J. P. & DUYCKAERTo,G., Inorg-nucl. chem. Lett .• 14 (1980), 233.

536

.9. ~N, F. A. & WINO, R. M., Inorg. Chern., 4,(1965),S67; LARSEN, M. L. & MOORE, F. W., Inorg, Chem .•5 (1986), SO.

10. MOORE, F. W. & RICE, R. E., Inorg. Chern" 7 (1968),'. 2SIO.11. SYAMAL, A. & SINOHAL,O. P., 7}ans. metal Chem .• 4

(1979), 179.

Spectroscopic & Thermal Studies on Zn(fi), Cd(ll) .&Hg(H) Complexes of 2-Amino-S-pbenyl-l,3,4-tbia-

diazole

J. SINOH·P. O. Department of Chemistry, U. P. College, Varanasi221 002

and

N. K. SINOHChemistry Department, Banaras Hindu University, Varanasi

221005

Received 17 August 19&1; revised and accepted 29 December 1981

c;ompIexes or Zn(ll), Cd(ll) and Hg(II) with 2-~5-pheayl-l,3,4-thiadiazole have been prepared and cbaracteri8edby analytical, IR and X-ray measurements. Kinetics or thermaldecomposition of the complexes have also been studied by notiugthe mass loss ror different time intervals at colL'itant temperature.~kinetic data suggest that the decomposition is a cUffusioIl-CODtroIled process.

A LARGE number of studies have been made onthe mechanism of the thermal decomposition of

simple as well as complex compounds, however, thedata on the kinetics of thermal decomposition oftransition metal complexes are limited=s, The pre-sent note describes the preparation, characterization,thermal behaviour and kinetics of thermal decom-position of the title complexes.

All the chemicals used were of AR(BDH) grade.The ligand, 2-amino-5-phenyl-l,3,4-thiadiazole (abb-reviated as APTH) was prepared by the method byRao and Srinivasan and its purity fully checked'.. All the complexes were prepared by refluxing the

respective metal chlorides with the ligand in 1:2molar ratio in aquo ethanol for 2-3 hr (ZnCI2 complexwas prepared in ethanol). The complexes werewashed with hot ethanol and water except ZnCI2-complex which was washed only with hot ethanol.The characterization data of the complexes aregiven below :

Found (Calc.), coComplex, .

Zn(APTH).CI.Cd(APTH).CI,Hg(APTH),CI.

N17.04(17.13~15.48 15.6313.82~13.42

S13·m13.0~11.58 1l.9()

. 10.62 10.02

M12.80(I3.3~20.84(20.0931.80(32.0

. Thermogravimetry of the complexes was performedon a manual therrnogravimetric analyser (F.C.I.Sindri, India) at a heating rate of 5°Cjmin in staticair. Qualitative analyses of the gases evolved duringthermal decomposition of the complexes were carried