CROATICA CHEMICA ACTA

CCA-1703

CCACAA 59 (4) 945-949 (1986)

YU ISSN 0011-1643UDC 546.881

Note

Spectral and Thermal Studies of 1,10-PhenanthrolineN,N' -Dioxide Chelates of Oxovanadium(IV)

R. K. Agarwal* and Gyanendra Singh

Department of Chemistry, Lajpat Rai Post-Graduate CoLLege, Sahibabad-201005,Ghaziabad (U. P.), India

Received May 17, 1985

A new series of penta-coordinated oxovanadium{IV) chelatesof 1,10-phenanthroline N,N'-dioxide (Phen02) have been synthe-sized and characterized by conductance, magnetic moments, in-frared, electronic spectra and TG-data.

INTRODUCTION

The coordination chemistry of aromatic amine N-oxides has been reviewedin recent years'. Of the heterocyclic N-oxides studied by far the largestamount of work has been carried out with pyridine N-oxide and 2,2'bipyridylN,N'-dioxide1• But the study of coordinating ability of a similar ligand, i. e.1,10-phenanthroline N,N'-dioxide, with metal ions is comparatively less2,3.Thus, it is worthwhile to study the ligational behaviour of 1,10-phenanthrolineN,N'-dioxide (Phen07.) with oxovanadium(IV).

EXPERIMENTAL

The Iigand Phen02 was prepared from 1,10-phenanthroline by the method des-cribed for 2,2'-bipyridyl N,N'-dioxide,3 while the Lewis acids were obtained asreported in ref. 4.

The complexes were prepared by mixing warm acetone solutions of oxovana-dium{IV) salts with PherrOj in the same solvent. In some cases, the preci pitati on ofthe complexes occurred on mixing the solutions while in the others, the precipitateswere obtained on keeping the mixtures on water bath for 5 minutes under stir ring.The solid products were collected, washed with ether and dried in vacuo over P205•

AnalyticaI procedureVanadium metal in all the complexes was estimated by EDTA titrations using

Erichrome Black-T as indicator and was confirmed by igniting the complexes inair and estimating the metal as V205. The halides in the complexes were estimatedby Volhard's method. The perchlorate was determined by the method of Kurz et al."All other physico-chemical studies of the complexes were made as reported earlier."

RESULTS AND DISCUSSION

The interaction of oxovanadium(IV) salts with PherrO, results in theformation of compounds of the general composition VOX2 . PherrO, (X = CLBr, I, NCS, N03 or C204 )and VO(Cl04h . 2Phen02. The analytical data aregiven in Table I. The compounds are quite stable and can be stored for a long

* Author for correspondence.

eo >I>-

(j)

TA

BLE

I

Ana

lytic

al,

Con

duct

ivity

and

Par

tial

IRD

ata

(cm

-1)

for

VO

++

Che

late

sof

Phe

n02

Foun

d(C

alcd

.)/O

/oQm

Ave

rage

Mol

.W

t.v

(N=O

)c:

5(N

-O)

v(M

-O)

Com

poun

doh

m1

ern"

(For

mul

aV

NA

nion

mol

'"W

t.)

Phen

0213

10s

855s

?J-

--

--

-12

80s

(':

845m

420m

:..V

OCh

.Phe

n02

14.3

97.

8120

.02

3.93

342

1280

so

(14.

57)

(8.0

0)(2

0.28

)(3

50)

1265

m:.. ;0

VO

Br2

.Phe

n02

11.4

26.

1235

.87

4.29

431

1290

m85

0m42

5m:;J :..

(11.

61)

(6.3

7)(3

6.44

)(4

39)

1270

mt-< ;J>

VO

h'Ph

errO

j9.

415.

0646

.82

5.33

528

1290

m84

5w43

0mZ

(9.5

6)(5

.25)

(47.

65)

(533

)12

80sh

tJ 0V

OC20

4.P

hen0

213

.73

7.44

-5.

1935

812

80s

850m

427w

(fJ(1

3.89

)(7

.62)

(367

)12

70sh

Z28

.05

5.16

1270

s85

0m43

0mo

VO

(Cl0

4l2

.2Ph

en02

7.21

3.87

233

~(7

.39)

(4.0

5)(2

8.84

)(6

90)

1240

m

VO

(NO

sl2

.Phe

rrO

',12

.43

13.6

9-

3.62

397

1280

m85

2m42

5m(1

2.65

)(1

3.89

)-

(403

)12

70sh

VO

(NCSl

2.P

hen0

212

.72

14.0

228

.82

5.26

387

1290

m86

0m42

0m(1

2.91

)(1

4.17

)(2

9.36

)(3

95)

1275

w

V-COMPLEXES 947

time. The compounds are fairly soluble in common organic solvents. Theelectrical conductances measured in nitrobenzene at room temperature (32°C)are consistant with the non-electrolytic nature of halo, pseudohalo, oxalatoand nitrato complexes, while the perchlorate complex is 1 : 2 electrolyte.

The room temperature magnetic moments of the complexes are in therange 1.72-1.80 B. M. These values correspond to one unpaired spin pervanadium atom, demonstrating the tetravalency of vanadium in the complexesand also the absence of metal-metal interaction between vanadium atoms.?

Infrared SpectraTable I records important IR bands for the ligand and the complexes.

In the IR spectra of the free ligand two (N-O) bands at 1310 and 1280 crn"have been observed-". These bands were shifted to lower frequencies uponcomplex formation. The decrease in the frequency of the V (N-O) vibrationis attributed to O-O chelation in PherrOj. Absorption of strong intensity at855 cm" has been assigned to NO bending mode, and from the tabulated datait appears that this absorption changes only slightly on complexationt=. Thisfurther supports oxygen linkage between metal and ligand. In the far IRregion the metal-ligand vibration is tentatively assigned to v (V-O) mode.

The bands due to the v {V=O) vibration occur in the 980-960 crn? region.These- values are in the range observed for monomeric VO++species in all thePherrO, complexes of oxovanadium(IV)1. However, it may be pointed out thatthe lower values of v (V=O) normally inferred" the polymeric nature of thecomplexes. But recent views indicate that solid state effects" and electron--withdrawing groupa'? can also cause a lowering of the v (V=O) frequency.

The ionic nature of the perchlorate group may be suggested by the pre-sence of a fairly broad v3, band at 1090 cm" and v, band at 625 cm" 4,11. Thethiocyanato complexes show three bands at 2080 (v C= N), 850 cm" (v C-S)and 460 cm? (O'NCS). This may be taken as an evidence of the bonding of thethiocyanate through nitrogen in the VO++cornplex'". The bidentate nature ofthe coordinated oxalate group, bonded covalently to the VO++moiety, isrevealed by the presence of V7, VI and v2 bands at 1715, 1650 and 1360, respec-tively!". In the IR spectra of VO(N03h' PhenN02, the bands appearing at1575 (VI), 1260 (V2), 1030 (V3) and 805 (V4) indicate the covalent nature of thenitrato groups in the complex-". The two combination bands appear at 1770and 1750 cm-I. By applying the 'Lever separation method!" the separation of20 cm" in this case suggests the monodentate nature of the nitrato groups.

Electronic SpectraThe electronic spectra of the complexes in CH3CN in the visible range

were taken. In all the chelates the bands occur in 12500-12800 cm" regionwith a shoulder in 15300-15700 cm" region. These bands are due to d-dtransition spectrum and can be assigned to dxy ~ dxz>dyz and dxy ~ dx'_/transitions, respectively. The band due to dxy ->- dz2 seems to have been maskedby the intense charge-transfer bands occuring in the UV region!",

In conclusion, in all these chelates the coordination number of vanadiumis five and the penta-coordinated oxovanadium(IV) complexes can have a tetra-gonal pyramidal structure.

( .

TABLE

II

Thermoanalytical

Results

Obtained

for

the

VO++

Cheuiies

ofPhen02

<:o ~ 00

Sample

Residual

Com

pound

Wto

mass

mg

mg

VOCb.Phen02

28.72

7.07

VOBr2

.PhenO

s30.16

5.76

VO(NCSh

.Phen02

27.32

6.17

VO(N03h

.Phen02

26.92

5.66

VOC204.Phen02

29.12

6.75

Massloss

(%)

140-220oC

280-

375O

C

Theor."

Exp.

Theor.b

Exp.

30.28

32.16

60.57

62.15

24.14

25.95

48.29

50.06

26.83

28.16

53.67

55.02

26.30

27.92

52.60

54.06

28.88

30.06

57.76

59.06

Residue

o/~

~53

00C

~Theor.e

Exp.

;.. o ;.. :ti26.00

24.65

:::: ;..20.72

19.12

l' ;..23..03

22.59

z tj22.58

21.06

0 ff)

24.79

23.19

H z o ~•Calculated

forloss

of.0.5

moleof

Iigand.

bCalculated

fortotalloss

ofIigand,

eCalculated

asV20S.

V-COMPLEXES 949

Thermal Studies

The results of thermal analysis of VO (IV) complexes are presented inTable II. The t. g. and d. t. curves of VO(IV) chelates of Phen'O, do not showthe presence of water molecules, either in or out of the coordination sphere.The t. g. curves show that all the chelates complete their decomposition pro-cess according to the following schemes:

VOX2 • PherrO, ~ VOX2 • O . 5Phen02 ~ VOX2 -? [VOz] ~ VzOs(X = Cl, Br, NCS, N03 or C204)

REFERENCE S

1. N. M. Karayannis, A. N. Spe,ca, D. E. Chasan, and L. L. Pytlew-s k i, Coord. Chem. Rev. 20 (1976) 37.

2. A. K. S r iva s t a v a, S h ash i S h a rrna, and R. K. Ag a r w a 1, Inorg.Chim. Acta 61 (1982) 235.

3. R. K. Ag a r w a 1, G y ane n d r a S i n g h, M. S r iva s t a v a, and A. K.S r iva st a v a, Thermochim. Acta 73 (1984) 243.

4. R. K. Ag a r w aland G y ane n d r a S i n g h, Thermochim. Acta (In Press).5. E. K u r z, G. K o b e r, and M. B e r l, AnaLyst Chem. 30 (1958) 1983.6. R. K. A g a r w a 1, A. K. S r iva s t a v a, and T. N. S r iva s t a v a, Tran-

sition Met. Chem. 5 (1980) 95.7. J. SeI b i n, Chem. Rev. 65 (1965) 153.8. R. L. F a r m e r and F. L. U r b a c h, Inorg. Chem. 13 (1974) 587.9. M. P a s qua t e, F. Mar c het t i, C. J. Flo ria n i, and S. Me r 1i n o,

J. Chem. Soc., DaHon Trans. (1977) 139.10. H. A. K u s k a and P. H. Y a n g, Inorg. Chem. 16 (1977) 1938.11. S. K. Ma dan and A. M. D o n o h u e, J. Inorg. NucL Chem. 28 (1966) 1303.12. J. L. B u r mei ste r, Coord. Chem. Rev. 1 (1968) 205; 3 (1966) 225.13. G. Du r g a Pra sad and C. C. Pat e 1, Indian J. Chem. 11 (1973) 1300.14. S. K. Sa h n i and S. K. S an gal, Synth. React. Inorg. Met.-Org. Chem.

8 (1978) 291.15. A. B. P. Lever, E. M o n tova n i, and B. S. Ram a s w amy, Can. .T.

Chem. 49 (1971) 1957.16. D. N. Sat h y ana ray ana and C. C. Pat e 1, Indian J. Chem. 5 (1967) 360.

SAŽETAK

Spektrometrijsko termometrijsko istraživanje kelatnih kompleksa vanadil-Ienas 1,10-fenantrolin N,N'-dioksidom

R. K. AgarwaL i G. Singh

Interakcijom vanadil-iona s 1,10-fenantrolin-N,N'-dioksidom (Phen O-) nastajuspojevi opće formule VOX2 . PherrOs (X = Cl, Br, I, NCS, N03 ili C20J) i VO(CI04l2 .. 2Phen02. Nastalim kompleksima snimljeni su IR i UV/VIS spektri, te je određenmagnetski moment i molarna provodnost. Kompleksi su također podvrgnuti terrnič-koj (TG i DT) analizi, koja je pokazala odsutnost molekula vode unutar koordina-cijske sfere centralnog iona i izvan nje.