Indian Journal of Chemi stry Vol. 40A, June 200 I, pp . 633-637 Some mononuclear titanium(IV) complexes of salicylidene anthranilic acid and o-vanillinoxime M S Sin gh* & Prem Narayan Department of Che mi stry, D D U Gorakhpur Universi ty, Gorakhpur 273 009 (UP). Ind ia ReceiFed 5 October / 999; revised I February 2000 Some mo nonucl ear tit anium(IV) complexes of sa li cy lid ene anthranilic acid (H"L 1 ) and o-vanillinoxime (H 2 L 2 ) have been sy nthe sized in a two step. one-pot procedure by the reactions of TiCI 4 and sodiu m salts of the li ga nd s in different stoichiometric ratios in good yields with an exce llent purity. Titani um tetrachlor id e' is a useful building block in sy nthesis . Numerous reac ti ons employ in g titanium te tr ach lo rid e and it s complexes as reagents have been repo rted and reviewed 2 · 3 . During the last decade gro up IV tra ns iti on metal chemistry has made a major co n- tribution in providing effective complexes fo r novel metal- ass isted organic transformations 4 - 6 . The sulphur and nit rogen containing complexes of t it anium(IV) are becoming more and more important fo r industrial app li cations 7 . The use of these derivatives as rea- ge nts 8, leaving gro up s or protective gro up s is now becomi ng co mm on in many of the reactions 9 · 10 . It be- came c le ar that th e transmetallation of classical "ca rb- anions" using t ita nating agents produces new rea- ge nts 11 whi ch di sp lay a high degree of chemo-, regia- and stereo-se lecti vit y. In spite of the considerable growth of literature on titanium(IV) complexes 12 · 13 co nt aining N, 0 and S donor ligand s, not much work is known abo ut the complexes of Ti ( IV ) with the title li ga nd s. The basic objective of th e prese nt study is to elicit information about the rel ative coo rdinatin g abil- ity of th e li ga nd s towards metal atom. In view of this, and in continuation of our earlier studies 14 - 16 on Ti(IY) complexes, we now describe some complexes of Ti(IV) with tit le Schiff bases. Experimental All manipulations were ca rri ed out under nitrogen atmosphere and with thoroughly dried solvents and gla ss ware. Chemicals and solvents used were dried an d puri fi ed by sta nd ard methods 17 . AR grade TiCI 4 fro m Ridea l-d e Haen AG Seelze-Hannover, Germany was used as such without further purification. Tita- nium(IV) wa s estimated grav imetrically as Ti0 2 , and chloride and sulphur were estimated gravi metrically as AgCI and BaS0 4 , respectively 17 • Nitrogen was de- termined by th e Kjeldahl's method 17 . IR spectra were recorded on a Perkin-Elmer model 577 spectrometer in the range 4000-200 em·' in KBr di scs . 1 H NMR spectra were recorded on a Bruker AC 250 MH z in- strument operating at 250MHz in CDCI 3 using TMS as an internal reference. Molecular wei ghts were de- termined by a Kn auer vapour pre ss ur e osmometer in dilute CHCh solution at 45°C. The li ga nd s N- (salicylidene)anthranilic ac id (H 2 L 1 ) and o-vanil- linoxime (H 2 L 2 ) were prepared by the li te rature meth- ods18' 1 9. The TLC analysis of th e Sc hi ff bases show a si ngle spot, different from that of the startin g materi- al s, indic atin g its purit y. H,L' II li 2 L 2 Their eleme nt al analysis correspond to the ex- pected formulae. The progress of the reaction was monitored by TLC on sili ca ge l plate. All th e melting points are uncorrected. Reaction between titanium( IV) chloride and the so- dium salt of N-( salicylidene)anthranilic acid in a 1:1 molar ratio (1 ). To a clear cold solution of sodium isopropoxid e prepared in situ by di sso luti on of sodium (0.065 g, 2.8 mmol) in isopropanol (2 5 ml ), N- (salicylidene)- anthranilic acid (0.68 g, 2 .8 mm ol) was added s lo wly, and the contents were refluxed 11ll· 4 h. After cooling, 0.54 g (2.8 mmol) of TiCI 4 in 15 ml of dry benzene was added dropwise, and the mixture was further re- fluxed for 2 h to ensure completion of the reacti on. After filtering off the precipitated NaCI, the de sired product (0.99 g, 89%) was isolated by evaporation of the solvent under reduced pressure. The product was further purified by crystallization using dichlo- romethane-n-hexane mixture. All other titanium(IY) derivatives of N-(salicylidene)anthranilic acid were synthesized ana lo gously. The pertine nt data for thi s and other derivati ves are li sted in Table 1.
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Indian Journal of Chemistry Vol. 40A, June 200 I, pp. 633-637
Some mononuclear titanium(IV) complexes of salicylidene anthranilic acid and
o-vanillinoxime
M S Singh* & Prem Narayan Department of Chemi stry, D D U Gorakhpur Universi ty,
Gorakhpur 273 009 (UP). Ind ia
ReceiFed 5 October / 999; revised I February 2000
Some mononucl ear titanium(IV) complexes of salicy lidene anthranilic acid (H"L1
) and o-vanillinoxime (H2L2) have been
sy nthesized in a two step. one-pot procedure by the reactions of TiCI4 and sodium salts of the li gands in different stoichiometric ratios in good yields with an exce llent purity.
Titanium tetrachloride' is a useful building block in synthesis . Numerous reactions employ ing titanium tetrach loride and its complexes as reagents have been reported and reviewed2
·3
. During the last decade group IV transition metal chemistry has made a major contribution in providing effective complexes fo r novel metal-ass isted organic transformations4
-6
. The sulphur and nitrogen containing complexes of titanium(IV) are becoming more and more important fo r industrial app li cations7
. The use of these derivatives as reagents8, leaving groups or protective groups is now becomi ng common in many of the reactions9
·10
. It became clear that the transmetallation of classical "carbanions" using titanating agents produces new reagents 11 which di splay a high degree of chemo-, regiaand stereo-selecti vity. Inspite of the considerable growth of literature on titanium(IV) complexes12·13
containing N, 0 and S donor ligands, not much work is known about the complexes of Ti (IV) with the title ligands. The basic objective of the present study is to elicit information about the rel ative coordinating ability of the ligands towards metal atom. In view of this, and in continuation of our earlier studies14-16 on Ti(IY) complexes, we now describe some complexes of Ti(IV) with title Schiff bases.
Experimental All manipulations were carri ed out under nitrogen
atmosphere and with thoroughly dried solvents and glassware. Chemicals and solvents used were dried and puri fied by standard methods17
. AR grade TiCI4 from Rideal-de Haen AG Seelze-Hannover, Germany
was used as such without further purification. Titanium(IV) was estimated grav imetrically as Ti02 , and chloride and sulphur were estimated gravi metrically as AgCI and BaS04, respectively 17
• Nitrogen was determined by the Kjeldahl's method 17
. IR spectra were recorded on a Perkin-Elmer model 577 spectrometer in the range 4000-200 em·' in KBr discs. 1H NMR spectra were recorded on a Bruker AC 250 MHz instrument operating at 250MHz in CDCI3 using TMS as an internal reference. Molecular weights were determined by a Knauer vapour pressure osmometer in dilute CHCh solution at 45°C. The li gands N(salicylidene)anthranilic ac id (H2L
1) and o-vanillinoxime (H2L2) were prepared by the li terature methods18'19. The TLC analysis of the Schi ff bases show a si ngle spot, different from that of the starting materials, indicating its purity.
H,L'
~OH
~H II
@(~oH ~
li2L2
Their elemental analysis correspond to the expected formulae. The progress of the reaction was monitored by TLC on silica gel plate. All the melting points are uncorrected .
Reaction between titanium( IV) chloride and the sodium salt of N-( salicylidene)anthranilic acid in a 1:1 molar ratio (1 ).
To a clear cold solution of sodium isopropoxide prepared in situ by di ssolution of sodium (0.065 g, 2.8 mmol) in isopropanol (25 ml ), N-(salicylidene)anthranilic acid (0.68 g, 2.8 mmol) was added slowly, and the contents were refluxed 11ll· 4 h. After cooling, 0.54 g (2.8 mmol) of TiCI4 in 15 ml of dry benzene was added dropwise, and the mixture was further refluxed for 2 h to ensure completion of the reaction. After filtering off the precipitated NaCI, the desired product (0.99 g, 89%) was isolated by evaporation of the solvent under reduced pressure. The product was further purified by crystallization using dichloromethane-n-hexane mixture. All other titanium(IY) derivatives of N-(salicylidene)anthranilic acid were synthesized analogously. The pertinent data for thi s and other derivati ves are li sted in Table 1.
0\ (.;.)
~
Table !-Characterizati on data of titanium (IV) complexes of N-(salicy lidene) anthrani lic acid and o-vanillinoxime
Compd Mol.wt.) Reactants g, (mmol) Molar Reflux Yield m. p. Found (Calcd),%
Found (Calcd. Ligand Sodiu m TiC14 ratio time (h) g (%) oc c H N Ti Cl
I. [CJ4HJON03]TiC l 3 0.68 0.064 0.54 1:1:1 6 0.99 164 42.22 2.22 3.32 12.06 26.89 395 (394.2) (2.8) (2.8) (2.8) (89) (42.62) (2.54) (3.55) (12. 15) (27.02)
2. [CJ 4H 10N03hTiC I2 0.57 0.055 0.22 2:2: 1 5 0.5 1 180 56.01 3.06 4.46 7.92 11.67 600 (598.7) (2.4) (2.4) ( 1.2) (73) (56. 12) (3.34) (4.68) (8.00) (1 1.86)
3. [CJ4HJONOJhTiC I 0.94 0.090 0.25 3:3:1 6 0.88 188 62.41 3.42 5.06 5.67 4.20 805 (803.2) (3.9) (3 .9) ( 1.3) (84) (62.75) (3 .74) (5 .23) (5.96) (4.42)
4. ICJ .J HJON03)4Ti 0.96 0.092 0.20 4:4: I 5 0.87 2 12 66.28 3.44 5.32 4.40 z 1009 ( 1007.7) (4.0) (4.0) ( 1.0) (84) (66.69) (3.97) (5 .56) (4. 75) 0
:;;: z
5. [C1 4H9N03]TiC l2 0.29 0.056 0.23 1:2: 1 4 0.32 2 13 46.62 2.26 3.72 13.02 19.70 '-
359 (357.7) ( 1.2) (2.4) ( 1.2) (76) (46.97) (2.52) (3.9 1) (13.39) (19 .85) n :I: tTl 3::
6. [C1 4H9N03hTi 0.28 0.05 1 0. 11 2:4: 1 6 0.22 183 63.42 3. 16 5.02 8.89 (/)
527 (525 .7) ( 1.2) (2.2) (0.58) (72) (63.9 1) (3.42) (5.33) (9. 11 ) tTl 0 )>
7. fC sHsN03]TiC I3 0.67 0.092 0.76 1:1:1 5 0.84 126 29.62 2.47 4.04 14.42 33.09 '-c
320 (320.2) (4.0) (4.0) (4.0) (66) (29.98) (2.50) (4.37) ( 14.96) (33.26) z tTl N 0
8. [C8H8N03h TiC 12 0.61 0.083 0.34 2:2:1 6 0.69 134 42.47 3.59 6.06 10.44 15.43 0
451 (450.7) (3 .6) (3.6) ( 1.8) (84) (42.60) (3.55) (6.2 1) (10.63) (15 .73)
9. [C8H8N03]JTiC I 0.55 0.077 0.2 1 3:3: 1 4 0.50 148 49.28 4.06 7.06 8.06 6.09 580 (58 1.2) (3.3) (3.3) ( 1.1 ) (79) (49.55) (4. 13) (7.23) (8.24) (6. 11 )
10. [CsH8N03]4 Ti 0.65 0.088 0. 18 4:4:1 5 0.46 74 53.69 4.53 7.4 1 6.8 1 712 (7 11.7) (3 .8) (3.8) (0.95) (66) (53.95) (4.50) (7.87) (6 .73)
ll. fC~H 7NO,]TiCl2 0.31 0.090 0.35 1:2: 1 4 0.36 LB .33.46 2.41 4.'18 16.6? 24KI 284 (283 .7) ( 1.8) (3 .9) ( 1.8) (69) (33.84) (2.47) (4.93) ( 16.88) (25.03)
12. [CsH1N03hTi 0.23 0.064 0. 13 2:4: 1 6 0.2 1 144 50.48 3.68 7.02 12.46 378 (377.7) ( 1.4) (2.8) (0.69) (80) (50.83) (3 .7 1) (7 .4 1) ( 12.68)
NOTES 635
Reaction between titanium( IV) chloride and the sodium salt of o-vanillinoxime in a 1:1 molar ratio (7)
Compound (7) was prepared by the reaction of ovanillinoxime (0.67 g, 4.0 mmol) with TiC14 (0.76 g, 4.0 mmol) in analogy to the procedure as mentioned earlier for compound 1. All other titanium(IV) derivatives of o-vanillinoxime were synthesized analogously (Table 1).
Results and discussion
Titanium(IV) derivatives of N-(salicylidene) anthranilic acid have been prepared by the reaction of titanium(IV) chloride with the sodium salt of N(salicylidene)anthranilic acid (prepared in situ) in different stoichiometric ratios in a refluxing dry benzene-isopropanol mixture. These reactions are found to be quite facile and the sodium chloride formed during the course of the reaction is filtered off.
•[:5: l+oN•~ "[®:;: l+T;CI, ~~:5~~TiCI lSJ-.c__..oH @:(_..ON•· lSJ-.c_ •~ I I I 0 o 0 n
where n =I, Compd 1; n = 2, Compd 2: n = 3, Compd 3; n = 4, Compd 4
Similarly the disodium salt of ligand are reacted with TiC14 in a I: I and 2: I molar ratios to give titanacyclic complexes.
where m = I, n = 2, Compd 5; m = 2, n = 4, Compd 6
Titanium(IV) derivatives of o-vanillinoxime have been synthesized by the reaction of titanium(IV) chloride and the sodium salt of o-vanillinoxime (prepared in situ) in different molar ratios.
[ CH-N-0] I):::ON•J ~ _.N'4'CI n L®:H, + n N• ~ n L~~ +liCI, ~N~ L ®:fljn
1
• •
where n = I, Compd 7; n = 2, Compd 8; n = 3, Compd 9; n = 4, Compd 10
Similarly, the disodium salt of the ligand is reacted with TiC14 in a I: I and 2: I molar ratios to give sevenmembered titanacyclic complexes.
where m =I, n = 2, Compd 11; m = 2, n = 4, Compd 12
All the resulting derivatives are coloured solids and soluble in common organic and coordinating solvents. These complexes are further purified by crystallization from dichloromethane-n-hexane mixure and their purity was further checked by TLC on silica gel . Each of the complexes moves as a single spot indicating the presence of only one component and hence their purity. Molecular weight determination in CHCb solution shows monomeric nature of these complexes. The conductivity measurements in nitrobenzene exhibit electrolytic nature of I: I, I :2 and I :3 reaction products, whereas no electrical conductivity is shown by I :4 reaction product. Elemental analyses are in the good agreement with the calculated values (Table I) .
The v(C=O) mode of the free -C02H group (H2L1)
at I675 em·' is not observed in complexes (1-6) and only Vas and Vs modes of deprotonated -C02 group appears at - I575 and I380 em·', respectively, the D.v(V35-V5) value (195 cm- 1
) being consistent with unidentate carboxylate coordination20
·21
• The v(C=N) frequency of the free ligand at I630 em·' are shifted to lower frequencies in all the complexes, suggesting coordination through azomethine nitrogen22
. In the complexes 5 and 6, the phenolic -OH disappears completely, indicating coordination via oxygen of the -OH group, while in complexes 1-4, appearing at - 3460 em·' in the free ligand, remains unaffected . These facts support coordination by the ligand as bidentate in the complexes 1-4 and tridentate in the complexes 5 and 6 using the -CH=N, -C02 and phenoxide groups23
.
The IR spectra of the complexes 7-12 have been compared with the corresponding ligand (H2L
2) and
from the shifts in frequency and/or from the intensity lowering, the coordination sites have been ascertained. The spectrum of vanillinoxime exhibits bands at I615 v (C=N) and 3300 em· ' v (0-H, N-OH and
636 INDIAN J CHEM, SEC. A, JUNE 2001
phenolic-OH). The presence of -OH vibrations in the complexes 7-10 shows that -OH groups are intact and uncoordinated, whereas in complexes 11 and 12, it disappears completely suggesting coordination via phenolic oxygen to titanium metal. There is no significant change in the (C=N) stretching frequency suggesting non-participation of azomethine group in coordination. The band appearing at 1030 em·' in the spectrum of the ligand has been assigned to -OCH3
group vibration. These bands do not show any significant change and remain almost unchanged in the spectra of the complexes. A new band present in the region 544-576 em·' may be attributed to Ti-0 stretching vibration24 in all the complexes.
The PMR spectrum of the ligand H2L1 is charac
terized by signals at 8 11.86, 10.02, 8.65 and 7.92-6.48 ppm, attributable to -COOH proton, phenolic -OH, azomethine proton and phenyl protons, respectively. The PMR spectra of the complexes 1 to 4 are devoid of signal at 11.86, suggesting deprotonation of -COOH group and subsequent involvement in coordination, whereas in complexes 5 and 6, both -COOH and -OH protons disappear, showing bonding from carboxylic as well as phenolic oxygen to titanium atom. The azomethine protons suffer deshielding in all the complexes, exhibiting coordination of azomethine nitrogen to titanium.
A comparison of the 1H NMR spectral data of the ligand o-vanillinoxime and titanium(IV) complexes provides interesting results. The =N-OH signal is absent in the spectra of the complexes 7-10, suggesting deprotonation and its subsequent involvement in coordination forming Ti-0 bond24
. The -OH signal observed at 8 13.47 in free ligand also disappeared in compounds 11 and 12, indicating deprotonation and taking part in bonding to titanium atom. The aromatic protons appear over the region 8 8.22-6.48 ppm in all the complexes. The pertinent spectral data of the compounds are listed below.
I IR (KBr): 1608 (C=N), 3465 (0-H), 1575, 1380 (COO), 566 (Ti-O)cm·'~ 1H NMR (8 ppm): 8.18-6.54 (m, 8H, ArH), 9.96 (s, 1H, OH), 8.97 (s, 1H, CH=N).
2 IR (KBr): 1612 (C=N), 3455 (0-H), 1570, 1375 (COO), 570 (Ti-O)cm-1; 1H NMR (8 ppm): 8.20-6.48 (m, 16H, ArH), 10.12 (s, 2H, OH), 8.99 (s, 2H, CH=N).
3 IR (KBr): 1615 (C=N), 3460 (0-H), 1580, 1385 (COO), 568 (Ti-O)cm-1; 1H NMR (8 ppm): 8.16-
6.52 (m, 24H, ArH), 10.06 (s, 3H, OH), 9.12 (s, 3H, CH=N).
4 IR (KBr) : 1610 (C=N), 3450 (0-H), 1585, 1390 (COO), 572 (Ti-O)cm-1; 1H NMR (8 ppm): 8.16-6.56 (m, 32H, ArH), 10.10 (s, 4H, OH), 9.06 (s, 4H, CH=N).
5 IR (KBr): 1614 (C=N), 1574, 1382 (COO), 576 (Ti-O)cm-1; 1H NMR ( 8 ppm): 8.22-6.46 (m, 8H, ArH, 8.60 (s, 1 H, CH=N).
6 IR (KBr): 1610 (C=N), 1575, 1385 (COO), 564 (Ti-O)cm-1; 1H NMR (8 ppm): 8.16-6.54 (m, 16H, ArH), 9.10 (s, 2H, CH=N).
7 IR (KBr): 1615 (C=N), 3225 (0-H), 562 (TiO)cm-1; 1H NMR (Oppm): 7.36-6.76 (m, 3H, ArH), 13.10 (s, 1 H, OH), 8.96 (s, 1 H, CH=N), 3.86 (s, 3H, OMe).
8 IR (KBr): 1618 (C=N), 3215 (0-H), 560 (TiO)cm·'; 11-I NMR (8 ppm): 7.42-6.80 (m, 6H, ArH) 12.96 (s, 2H, OH), 8.92 (s, 2H, CH=N), 3.82 (s, 6H, OMe).
9 IR (KBr): 1614 (C=N), 3220 (0-H), 576 (TiO)cm-1; 1H NMR (8 ppm): 7.46-6.88 (m, 9H, ArH) 13 .16 (s, 3H, OH), 8.96 (s, 3H, CH=N), 3.88 (s, 9H, OMe).
10 IR (KBr): 1620 (C=N), 3210 ( 0-H), 572 (TiO)cm·'; 1H NMR (8 ppm): 7.45-6.78 (m, 12H, ArH) 13.12 (s, 4H, OH), 8.98 (s, 4H, CH=N), 3.78 (s, 12H, OMe).
II IR (KBr): 1613 (C=N), 556 (Ti-O)cm·'; 1H NMR (8 ppm): 7.38-6.82 (m, 3H, ArH), 8.94 (s, 1H, CH=N), 3.84 (s, 3H, OMe).
12 IR (KBr): 1615 (C=N), 544 (Ti-O)cm-1; 1H NMR (8 ppm): 7.42-6.86 (m, 6H, ArH), 8.92 (s, 2H, CH=N), 3.80 (s, 6H, Ome).
The above studies indicate that the ligands (H2L 1
and H2L2) act as unidentate to tridentate mode of at
tachment to the metal atom under different reaction conditions. The central titanium atom appears to acquire coordination numbers four, five, six, seven and eight in different complexes.
References I Mukaiyama T, Angew Chem, 89 (1977) 858; Comprehensive
organic chemistry, edited by D H R Barton & W. D.Ollis, (Pergamon Press, Oxford) 1979.
2 Manek E, Hinz D & Meyer G, Coord chem Rev, 164 (1997) 5.
3 (a) Sayeed AM, lftikhar K & Ahmad N, Indian J Chem, 34A (1995) 79 (b) Fokken S, Spaniol T P & Okuda J, Organometallics, 16 (1997) 4240
NOTES 637
(c) Guerin F, McConville D H & Payne N C, Organometallics, 15 ( 1996) 5085.
4 Erker G, Kruger C & Muller G, Adv organometal Chem, 24 ( 1985) I.
5 Erker G & Pfaff R, Organometallics, 12 ( 1993) 1921 . 6 Negishi E I & Takahashi T , Ace chem Res; 27 (1994) 124
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II Fokken S, Spaniol T P, Kang H-C, Massa W & Okuda J, Organometallics, 15 (1996) 5069.
12 Mack H & Ei sen M S, 1 chem Soc, Dalton Trans, 917 (1998).
13 (a) Hagadorn 1 R & Arnold 1, Organometallics, 17 (1998) 1355. (b) Tamayo P, Mendiola M & Masaguer 1 R, Trans met Chem, 14 ( 1989) 283.
14 Singh M S, Khan S & Tripathi U N, Phosphorus, sulfur, Silicon, 130 (1997) I 07 .
15 Singh M S, Narayan P & Singh A K, Phosphorus, sulfur, Silicon, !55 (1999) 298.
16 Singh M S & Narayan P, Synth react inorg met-org chem, 30 (2000) 1007.
17 (a) Armarego W L F & Perrin D D, Purification of laboratory chemicals, 4th Edn (Butterworth, Heinemann, Oxford, OX2 8DP) 1997.
(b) Furniss B S, Hannaford A 1, Smith P W G & Tatchell A R, Vogel 's text book of practical organic chemistry, 5th Edn (Longman, London) 1989.
18 Saha M C, Roy R, Ghosh M K & Roy P S, Indian J Chem, 26A ( 1987) 48.
19 Reddy K H, Indian J Chem, 29A (1990) 497.
20 Casellato U, Vigato P A & Vidali M, Coord chem Rev, 26 (1978) 85 .
21 Deacon G B & Phillips R J , Coord chem Rev, 33 ( 1980) 227.
22 (a) Kovacic 1 E, Spectrochim Acta, 23A ( 1967) 183
(b) Rao R 1 & Wankhade H B, Synth react inorg met-Org Chem, 25 (1995) 1049.
23 Dawes H M, Waters 1 M & Waters TN, lnorg chim Acta, 66 (1982) 29.
24 (a) Gainsford G J, Kemmitt T , Lensink C & Miles tone N B. lnorg Chem, 34 ( 1995) 746.
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