Indian Journal of ChemistryVol. 31A, January 1992, pp. 61-63

Synthesis and characterisation of bis( TIs -cyclopentadienyl )-N,N'-disubstituted

schiff base complexes of titanium( IV)

Virendra Joshi & Narender K Kaushik"Department of Chemistry, University of Delhi, Delhi 110007

Received 5 August 1991; revised and accepted19 November 1991

Titanium(IV) complexes of the type (CsHshTi(SB)have been prepared where (CsHslz =dicyclopentadieileand SB = tetradentate schiff base like N,N'-bis(arylidene)alkylenediamine, derived from the reaction of salicy-laldehyde and 2-hydroxy-l-naphthaldehyde with the di-amines of the type NH~XNH~ [X = - CH~ - CH~ -,-CH~ -CH2 - CHz -, - CH~ -(CH2)~- CH~ - J in 1:1molar ratio in tetrahydrofuran medium in the presenceof triethylamine. The complexes have been character-ised on the basis of elemental analysis, conductancemeasurements and spectral (IR, UV and 'H NMR) stud-ies.

We have earlier reported that the coordination oftwo oxygens and two nitrogens around the ("S_CsHsh Tiz + moiety weakens the cyclopentadienyl-metal bond' . Some derivatives of bis{cyclopentadie-nyl)titanium(IV) with quadridentate schiff baseshave been reported+'. We report in this note thereactions of bis( 115-cyclopentadienyl)titanium{IV)dichloride with some schiff bases and characterisa-tion of the complexes so formed.

ExperimentalAll the reagents used were of AR ,grade. Bis(,,5-

cyclopentadienyl )titanium{IV) dichloride,(C,HshTiCI2, was prepared by the reaction of sodi-um cyclopentadiene suspension with anhydrous ti-tanium tetrachloride in tetrahydrofuran, The sol-vents were dried as per literature methods", Nitro-benzene was purified by the method of Fay et aUTitanium was determined by gravimetric method astitanium oxide. Nitrogen was estimated by the Mes-senger's method".

Conductance measurements were performed innitrobenzene at 30 + OSC using an Elico conduc-tivity bridge mod~ICM~82. Infrared spectra wererecorded in nujol on a$himadzu-MOOEL-435 in-strument, in the region 4000-400 ern - '. The 'HNMR spectra were recorded in COCl, on a Hitachi-R-600 F7 spectrometer. .

UV spectra of the complexes were recorded inacetone on a Shimadzu UV-vis spectrometer, model431 in the region 109-900 nm.

Preparation of schiff basesTo a solution of the amine (0.10 mol in 100 ml of

freshly distilled ethanol). salicylaldehyde or 2-hy-droxy-l-naphthaldehyde (0.20 mol in 100 ml offreshly distilled ethanol) was added dropwise withvigorous stirring when the product precipitated im-mediately. The mixture was refluxed for half anhour, then cooled in an ice bath and filtered. Theproduct was recrystallised from hot ethanol, washedwith ether and dried in vacuo. The reaction involvedin the schiff base formation may be represented byEq.l.

R(OH)CHO + HzNXNH2 + OHC(OH)R - 2H2<;'

R(OH)CHN - X - NCH(OH)R ... (1)

Preparation of schiff base complexesAll the operations were carried out under strictly

anhydrous conditions. The schiff base and(CsHshTiC12 were taken in 1:1 molar ratio in THFin the presence of triethylamine and mixture wasrefluxed for 10 to 12 hr; the precipitated Et3NCIwas separated by filteration and volume of filtratewas reduced by half through evaporation of the sol-vent under reduced pressure. The product was ex-tracted from solution with hexane and dried in va~uo at room temperature. The reaction involved inthe complex formation may be represented by Eq.(2).

(CsHshTi{SB)+2Et3NCI ... (2)All the schiff base complexes crystallise as yellow-

ish brown powders. They arehighly soluble in or-ganic solvents like benzene, TIff. chloroform, ni-trobenzene etc. The molar conductanneof the com-plexes in 10- )M solution in ni~rqOO,nzeqe.werefound to be of theorder of 0.5 ohm-'- f ern", Thesevalues suggest the nonionic nature of the complexes(Table 1). ..-

62 INDIAN J CHEM, SEC. A, JANUARY 1992

ComplexesTable I-Analytical data of the complexes

Yield %R>und(%)

Ti N75 8.74 2.8478 8.75 2.7376 8.76 2.6274 8.79 2.9280 8.70 2.5882 8.71 2.69

('1sCsHshTi N,N'-bis(salicylidene)ethylenediamine('1sCsHs hTi N,N' -bis(salicylidene lpropylenediamine('1sCsHsh Ti N,N'-bis(salicylidene)hexamethy1enediamine

('1sCsHsh Ti N,N'-bis( 2-hydroxy-l-naphthalidene )-ethylenediamine('1ZCsHshTi N,N'-bis(2-hydroxy-l-naphthalidene)-propylenediamine('1sCsHsh Ti N,N'-bis(2-hy!jroxy-l-naphthalidene)-hexamethylenediamine

Results and discussionIR absorption bands at 3100 em - I (...c - H),

1450 cm-I (...c-C) 1015 cm-' (b in-plane C-H)and 810 em - I (b o.p C - H) indicate the presence ofcyclopentadiene group. A high intensity band as-signable to vC = N is observed at 1625 cm - I in thespectrum of the schiff base. In the complexes thisband is slightly shifted to the lower side (1600 em - I)indicating coordination of nitrogen to the metal-".The band due to vC - 0 mode in the complexes isobserved at a higher frequency (1320-1310 ern -I) ascompared to its position in the corresponding schiffbase indicating coordination through oxygen. Bandsin the regions 570-540, 525-425 em - 1are attribut-ed to vTiO and vTiN respectively.

The 'H NMR signal due to azomethine protonappears at b 8.82 ppm showing a downfield shift ascompared to the position in the correspondingschiff base ligand (b 8.45 ppm) indicating its desh-ielding as a result of coordination through nitrogenof azomethine group to titanium.

Aromatic protons which give signal at b 8.80-7.70 ppm (multiplet) show the downfield shift com-pared to signals in the schiff base spectrum. Thisdownfield shift also supports the coordination ofazomethine nitrogen of schiff base to the metal.

Additional signals due to - OC6H6 and- OC WHH were observed in the spectra ofthe com-plexes as triplets at b 3.48-b 3.80 ppm. The disap-pearance of the phenolic - OH proton signal inschiff base complexes indicates its deprotonation".

The visible spectra of the complexes exhibited aband in the 250-350 DID region which may be as-signed to charge transfer" - II.Three bands were ob-served at 250, 320 and 385 nm corresponding tothe 1£-1£* (benzenoid), 1£-1£* (azomethine) andn - jt* (azomethine) transitions respectively. In thescruff bases, the first two bands were observed at- 425 DID. The shift may be due to donation of lonepair of electrons by the nitrogen of azomethinegroup to the central metal atom '.

NMR spectra of these complexes were analysed

CU)

where R'= -CH2-CH2-;-CH -CH -CH -' -CH -(CH ) -CH -'2 2 2, 2 24 2,X = C6H4, CIOH6

by planimetric integration which conform to the for-mula (Tl5-C5H5hTi(NCH)2R'02X2, whereR'= -CH2-CH2-; -CH2-CH2-CH2-;

-CH2 -(CH2)4 -CH2 - and X=C6H4; CIOH6•

IH NMR data indicate that titanium{IV) has aplanar configuration in view of singlet signals forHC = N and NR protons. Sharp signals are ob-served for CSH5{Cp) in the the complexes whichsuggest the arrangement (1)12-14.

Based upon the spectral studies structure{II) maytentatively be assigned to these complexes.

rJ

Such a structure would maximise the coordinationnumber of metal ion as well as the total metal ringoverlap.References

1 Sodhi G S Kumar S & Kaushik NK, Acta chem hung, 114(3-4) (1983) 329.

2 Gupta G, Sharan R & Kapoor R N. Transition Met Chem, 3(1970) 282.

3 Sharma R K, Singh R V & Tandon J P, J inorg nucl Chern, 42(1980) 1382.

4 Vogel A t, A TeXTbook of practical organic chemistry, (Long-man Green, London) 197H.

5 Fay R C & Lowry R N, lnorg Chern, 6 (1967) 1512.6 Vogel AI, A text book of quantitative inorganic analysis

(Longman Green, London) 1978.

,

NOTES 63

7 Uttam Chandani J & Kapoor R N, Transition Met Chem, 3(1978)79.

8 Sharma A K, Khera B & Kaushik N K, Acta chem hung.115(2)(1984) 123.

9 Kaushik N K, Bhushan B & Chhatwal G R, Transition MetChern, 3 (1978) 215.

10 Kaushik N K, Bhushan B & Chhatwa1 G R, Synth React in-org met-org Chem, 8 (1978) 467.

11 Dorian P B, Patterson H H & Jordan PC, J chem Phys, 49(1968) 3845.

12 Dey K, Kumar D. Biswas A K & Ray S, J chem Sac. (1982)911.

13 Dey K, Ray S & Bandopadhyaya D, Proc Nat Acad Sci.India, 59(A) II (1989) 179.

14 Pokhariyal G, Proc Nat Acad Sci.. India, 58(A) III (1988)369.