Indian Journal of ChemistryVol. 28A, December 1989, pp. 1112-1114

Heterocyclic carboxylates of organotitani-um(IV) and organozirconium(IV)

Ajay K Bliagi, Bijendra Singh & Ramesh N Kapoor*Department of Chemistry, University of Delhi, Delhi 110007

Reeeived-e-January 1989; revised and accepted 8 May 1989(The complexes of the types [Cp2M(A)CI] and

[Cp2M(A)2) (where Cp = cyclopentadienyl; M =Ti or Zr;A=monobasic anion of 3-indoleacetic acid, 3-indole-propionic acid, 3-indolebutyric acid or I-tryptophan)have been synthesized by reaction of dichlorobis(cyclop-entadienyl)titanium(IV) (Cp2TiCI2) or dichlorobis(cyc-lopentadienyl)zirconium(IV) (Cp2ZrCh) with heterocyc-lic carboxylic acids in 1:1 and 1:2 molar ratios. The newcomplexes have been characterized by their elemental an-alyses, conductivity measurements, electronic, IR and IHNMR spectral studies.

Interest in metallocene chemistry may be attributedpartly to the application of such compounds as antitu-mour, radio pharmaceutical agents, etc.I-7. Severalindolecarboxylic acids and their derivatives have alsobeen investigated for anticancer effects=", Recently,Kapoor and coworkers 10,11have reported the reac-tions of thiophenecarboxylic acids and nicotinic acidswith Cp2TiCl2 and CP2ZrCl2 where some interestingresults were obtained. A survey ofliterature revealedthat no work has been carried out on the reaction of3-indoleacetic acid (IAH), 3~indolepropionic acid(IPH), I-tryptophan (TRH) and 3-indolebutyric acid(IDH) with Cp2TiCl2 and CP2ZrCI2' It was, therefore,considered of interest to synthesize and characterizethese heterocyclic carboxylates of organotitani-um(IV) and organozirconium(IV).

~eH2eOOH~N.!l

H3 -tnootecceuc cc.d (I AH)

~(eH2)2 -eOOH

~N]H

3 -Jndotepr cptontc acid (I PH)

~(HT1H-eOOH

VwlJ NHH 2

1- Tr yplophan (TRH)

~(CH2)feOOH

~NYH

3-1ndol<bulyric acid (I BH)

ExperimentalCp2TiCi2 and Cp2ZrCh were prepared by known

methods 12.13.Metals were estimated gravimetrical-ly'" as M02 and cWorine as AgCl. Nitrogen was esti-mated by Kjeldahl method and carboxylate group by

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a reported method 15.IH NMR spectra were recordedon a Hitachi R-600 rr NMR spectrometer. IR spect-ra were recorded in KBr on a Perkin Elmer 1710 F'TIR spectrometer 'in the range 4000-400 em - I.Theelectronic spectra were recorded on a Shimazdu UV-260 spectrophotometer in DMF. Conductance mea-surements were carried out on a Leeds Northrup(4959) electrolytic conductance bridge using DMF asa solvent.

Synthesis of metal carboxylatesFor the synthesis of the metal carboxylates of

CP2TiCl2 and CP2ZrCI2' Cp2MCl2 (M = Ti or Zr) andIAH, IPH, TRH or IDH were reacted (in stoichiomet-ric ratios) using anhydrous THF as the solvent andtriethylamine as the proton acceptor. The reactionmixture was stirred for - 40 hr at room temperature.The precipitated triethylamine hydrochloride was fil-tered off, dried and weighed to check the completionof the reaction. The solvent was removed from thefiltrate under reduced pressure. The products thusobtained were recrystallised from n-Hexane-THFmixture. Colour, melting point and analytical data ofthe complexes are given in Table 1.

Results and discussionCp2TiCl2 and CP2ZrCl2 react with heterocyclic

carboxylic acids (AH) inTHF in the presence of trie-thylamine in 1:1 and 1:2 molar ratios according to thefollowing equation:

THFCp2MCl2 + nAH + nEt3N--'.-"--.---stunngatR.T.

Cp2MCI2-n(A)n +nEt3N.HCl~(where M = Ti and Zr; n = 1 and 2; AH = IAH, IPH,TRHandIDH)These carboxylates are crystalline solids, suscepti-

ble to hydrolysis and soluble in polar solvents.IR spectra of the free acids show strong absorptions

at -1720 (vasCOO) and -1210 cm-I (vsCOO)16.These bands are shifted in the corresponding sodiumsalts 16and the shifts are even more prominent in orga-notitanium and zirconium carboxylates. The posi-tions of these absorption bands and /).v(/).v = vas- V s)values obtained have been summarized in Table 2.The low values of /).v in metal complexes 17.18(in com-parison to the corresponding values for sodium saltsof acids), presence of bands in the region 920-720em - 1(cip CO2) and a strong band observed at - 560

NOTES

Table I-Characterization data

Complex Colour Found (Calc.) (%)

(M.P.,°C)Metal Nitrogen Chlorine Carboxylate(M) (N) (Cl) (RCOO-)

[CpzTi(IA)Cll Opaque red 12.1 '3.4 9.0(76) (12.3) (3.6) (9.2)

[CpzTi(IAhl Red 9.0 5.2 65.8(85) (9.1) (5.3) (66.2;

[CpzZr(IA)Cll Light yellow 21.1 3.0 8.0(78) (21.2) (3.2) (8.2)

[CpzZr(IAhl Golden yellow 16.0 4.8 61.3

(87) (16.0) (4.9) (61.2)

[CpzTi(IP)Cll Red 11.7 8.7(91) (11.9) (8.8)

[Cp2Ti(IPhl Brick red 8.5 5.2 68.1(97) ( 8.6) (5.1) (67.9)

[Cp2Zr(IP)Cll Light brown 20.3 7.8(94) (20.5) (8.0)

[CpzZr(IPhl Brown 15.1 4.6 63.3(101) (15.3) (4.7) (63.0)

[CP2Ti(TR)Cll Orange 11.3 8.4

(120 dec.) (11.5) (8.5).

[Cp2Ti(TRhl Light orange 7.9 9.6 69.8(130 dec.) (8.2) (9.6) ~ (69.5)

[Cp2Zr(TR)Cll Yellow 19.6 7.5(122 dec.) (19.8) (7.7)

[CpzZr(TRhl Dark yellow 14.4 8.7 65.0(130 dec.) (14.5) (8.9) (64.7)

[CpzTi(IB)Cll Light brown 11.4 8.3(101) (11.5) (8.5)

[CpzTi(IBhl Brown 8.2 4.6 69.1(105) (8.2) (4.8) (69.4)

[Cp2Zr(IB)Cll Light brown 19.7 2.7 7.6(107) (19.9) (3.0) (7.7)

[Cp2Zr(IBhl Golden yellow. 14.5 63.9((112) (14.6) (64.6)

cm -I due to bopC02 (which should be absent in casecarboxylate ion is acting as a bridging ligand)'? sug-gest that carboxylate ion acts as a chelating bidentateligand. The metal complexes absorb strongly in theregion 3440-3380 cm -I due to (vN - H) and at -740 cm-I (bopC - H) as in free acids, indicating thatheteronitrogen is not involved in coordination 16,18.

No change is observed in vN - H ( - 3200 ern - I) ofNH2 for the metal complexes formed by TRH sug-gesting that NH2 group is free and does not take partin the coordination. IR spectra of metal complexes al-so exhibit the usual absorptions due to cyclopentadie-nyl group'P-". A band in the region500-420 em -I canbe assigned to metal-oxygen stretching vibration IU,II.

I

j H NMR spectra of metal complexes showed asharp singlet at - b6.4 ppm due to protons of cyclop-entadienyl groups (Table 2). A multiplet (characteris-tic of 3-indole derivatives) observed in the region06.9 to 8.2 ppm is assignable to indole ring protons.The N-H protons and alkyl chain protons resonate atthe same positions in the metal complexes as found in-the free acids.

The electronic spectra of the complexes show ab-sorption in the region 290-265 nm which can be as-signed to charge transfer transitionl'''! (Table 2).

The low values of molar conductance (10 - 4 to 10 - 3

mho em? mol- I) suggested the non-electrolytic na-ture of metal complexes in DMF solution. On the ba-

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INDIAN J CHEM, SEC A, DECEMBER 1989

Table 2-Spectral data of the complexes AcknowledgementOne of the authors (AKB) is thankful to the UGC,

Complex IR(cm-l) PMR, Electronic New Delhi for financial support.o(ppm) (nm)

V.,COO ",COO fj.v CsHs I...max References,

.(inDMF) Miller M, Paterson L C, Hansen F B & Nicholls P, BiochemJ,

[Cp2Ti(IA)CI] 1530 1426 104 6A 267A184(1979) 125,

(1576 )* (1404) (172) 2 KopfH & Kopf-Maier P,AngewChemlnt Ed(Eng), 18 (1979)477,

[Cp2Ti(IAhl 1528 1422 106 6.3 267.4 3 Cuingnet E, Sergheraert C, Tartar j.. & Dautrevaux M, J orga-[Cp2Zr(IA)Cll 1550 1430 120 6,5 282.4 nomet Chem, 195 (1980) 325,[Cp2Zr(IA)21 1546 1430 116 6,2 282,0 4 Cuingnet E, Dautrevaux M, Sergheraert C & Tartar A, Eur J[Cp2Ti(IP)Cll 1528 1429 99 6A 267,6 Med Chem-Chim Ther, 17 (1982) 203,

(1538) (1415) (123) 5 XuW,LuP, LuJ,YangY,ZhangX,ZhandS&XuB, YoujiHu-[Cp2Ti(IP)21 1526 1429 97 6.2 268,0 axue, 5 (1984) 366; ChemAbstr, 102 (1985) 79039,

[Cp2Zr(IP)Cll 1522 1428 94 6,5 280,0 6 Komicker W A & Vallee B L, AnnN YAcadSci, 153 (1969)

[Cp2Zr(IPhl 1520 1428 92 6,3 282,0 689,

[Cp2Ti(TR)Cll 1557 1448 109 6A 267,8 7 Edwards J A, Vrsillo R C & Hoke J E, Br J Haematol, 28

[Cp2Ti(TRhl 1555 1446 109 6.3 267,0(1974) 445,

[Cp2Zr(TR)Cll 1560 1445 115 6A 288.2 8 Bounan M, ChemAbstr, 108 (1988) 173563,

[Cp2Zr(TRhl 1540 1420 120 6,2 280A 9 Lumme P, Elo H & Janne J, lnorg chimActa, 92 (1984) 241.

[CpzTi(IB)Cll 1535 1422 113 6,5 266A 10 Dixit S C, Sharan R & Kapoor R N, lnorg chim Acta, 145(1572) (1418) (154) (1988) 39,

[Cp2Ti(IBhl 1524 1422 102 6,3 284,2 11 Dixit S C, Sharan R & Kapoor R N, lnorg chim Acta, 133

[Cp2Zr(IB)Cll 1526 1430 96 6A 266,8 (1987) 251.

[Cp2Zr(IBhl 1520 1426 94 6.3 284A 12 Willdnson G & Birmingham J M, JAm chem Soc, 76 (1954)

* Values of sodium salts of carboxylic acids are given in4281.

13 Eisch J J & King R B, Organometallic syn1hesis, Vol I, (Acad-parentheses emic Press, New York) 1965,

14 Vogel A I, Text book of quantitative inorganic analysis (Long-sis of above spectral features and other studies, the man, London), 1986, 4th Edn.

following modes (I, II) of coordination can be pro- 15 Mehrotra R C & Parashar G K, Synth React inorg met-org

posed for these heterocyclic carboxylates: Chem,8(2)(1978) 195,16 Micera G, Striuna E L, Panzanelli A, Pin P & Casiati F, J coord

Cp 0

Cp ~o ~Chem, 13 (1984) 231.<, /', <, ,~ 17 Mahar K R, Solanki A K & Bhandari A M, Synth React inorg/1"- ~C-R M >:-R

Co 0 C6 0.7 met-org Chern, 12(7) (1982) 805,CI 18 Solanki A K, Mahar K R & Bhandari AM, Synth React inorg

2

[CP2M(A)CI] [COZM(A )zJmet-org Chern, 8(4) (1978) 335,

19 Oldham C, Comprehensive coordination chemistry, Vol 2(I) (ll ) (Pergamon Press, London) 1987,435-440,

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