- Email: [email protected]
Template synthesis of iron(II), cobalt(II), copper(II) and zinc(II) complexes of diamidediimine macrocycles
Pergamon
0277-5387(W)EOO!W-X
Polyhedron Vol. 13, No. 15116, pp. 2319-2325, 1994 Ekwier science Ltd Printed in Great Britain 0277-5387p4 $7.00+0.00
TEMPLATE SYNTHESIS OF IRON@), COBALT(D), COPPER@) and ZINC@) COMPLEXES OF DIAMIDEDIIMINE MACROCYCLES MOHAMMAD
SHAKIR,*
SAJI P. VARKEY, FARHA FIRDAUS and HAMEED
P. SHAHUL
Division of Inorganic Chemistry, Department of Chemistry, Aligarh Muslim University, Aligarh 202 002, India (Received
17 January 1994 ; accepted 1 March 1994)
Abstract-A
series of iron( cobalt(II), copper(I1) and zinc(I1) complexes containing tetraazamacrocyclic ligands have been prepared by the condensation of 1,2-diaminoethane, 1,3-diaminopropane and ortho-phenylene diamine with methyl acetoacetate or ethyl acetoacetate in the presence of iron( cobalt(II), copper(I1) and zinc(I1) salts at room temperature. The structure and bonding of macrocyclic ligands have been studied from elemental analysis, magnetic susceptibility measurements, IR, ‘H NMR, mass, EPR and electronic spectra of the complexes. The stereochemistry around the metal ions is octahedral in which four of the coordination sites are occupied by the nitrogens of the macrocyclic ligand and the remaining octahedral positions are occupied by two chlorines.
The design and synthesis of polyazamacrocycles have attracted increasing interest in recent years for the possible relevance of these compounds as model’*2 ligands for metal enzymes and metal proteins as metal-ion selective ligands. Synthesis of organic substrates that preferentially interact with particular metal ions is of fundamental importance to many areas of chemistry.3 Condensation reactions between dicarbonyls and primary diamines have played an important role in the development of synthetic macrocyclic ligands which have been proved to be a fruitful source of imino macrocycles.4,21Usually such syntheses were carried out in the presence of a suitable metal ion which serves to direct the steric course of the reaction preferentially towards cyclic rather than oligomeric or polymeric products.4d Of the polyazamacrocycles, the tetraaza group has been the most intensively studied because of its great biological importance. Relative to their open-chain analogues, macrocyclic ligands have further stereochemical contraints associated with their cyclic nature which may influence their
*Author to whom correspondence should be addressed.
potential for metal ion recognition.7 For macrocycles incorporating rigid or semi-rigid cavities, recognition (and hence discrimination) may be associated with a close match or otherwise of the radius of the metal ion for the cavity.3 Kimura and co-workers have reported’ a series of diamide macrocycles and their applications. Recently we have reported9,“‘*” the synthesis and characterization of tetraazamacrocyclic complexes bearing the polyamide group and dithiadiazamacrocyclic complexes. Herein we report the synthesis and characterization of diamidediimine tetraazamacrocyclic complexes, [ML,Cl+ [ML,ClJ and wL’,Cl,]-[ML;Cl,] [M = Fe”, Co”, Cu” and Zn”), which resulted from the condensation of methylacetoacetate or ethylacetoacetate and diamines in the presence of metal salts EXPERIMENTAL
The chemicals, methyl acetoacetate, ethyl acetoacetate, 1,3-diaminopropane, 1,Zdiaminoethane and ortho-phenylene diamine (all E. Merck) were used as received. FeCl, * 6H2O, CoC12* 6H2O,
2319
2320
M. SHAKIR et al.
CuCl, * 2Hz0 and ZnCl, (BDH) were commercially pure samples and were dehydrated with acetic anhydride. All the solvents were dried before use. Preparation of dichloro(5,12-dioxa-l,lCdimethyl1,4,&l 1-tetraazacyclotetradeca-1 ,&diene) metaZ(II), [ML&l or [ML’, Clz] (M = Fe”, Co’i, Cu” or Zn”)
A methanolic solution (50 cm3) of ethylene diamine (20 mmol) was added dropwise with stirring to a methanolic solution (50 cm3) of the anhydrous metal chloride (10 mmol). After the addition of all the diamine, the contents were stirred for 1 h, followed by the addition of a methanolic solution (50 cm3) of methyl acetoacetate or ethyl acetoacetate (20 mmol) and stirred for a further 16 h at room temperature, resulting in the formation of the macrocyclic complexes [ML,C12] or [ML’, Cl*] (M = Fe”, Co”, Cu” or Zn”). The microcrystalline products thus formed were filtered, washed several times with methanol and dried in uacuo. All the experiments were carried out under dry nitrogen. Preparation
of dichloro(6,14-dioxa-8,16-dimethyl-
1,5,9,13-tetraazacyclohexadeca- 1,9-diene) metal(I1) and dichloro(2,3 : 9,10-dibenzo-5,12-dioxa-7,14-d& methyl - 1,4,&l 1 - tetraazacyclotetradeca - 1,8 - diene) metal(I1) [ML,Cld or [ML;Cl,] and [ML,ClJ or [ML;Cl,] (M = Fe”, Co”, Cu” or Zn”)
These compounds were prepared and isolated by the same procedure as described above. Here 1,3propanediamine and ortho-phenylenediamines were employed instead of ethylenediamine. Elemental analyses for C, H, N and mass spectra (JMSD-300) were obtained from the Microanalytical Laboratory of CDRI, Lucknow, India. ‘H NMR spectra were determined in DMSO-d6
using a Bruker AC 200E NMR spectrometer with Me,Si as an internal standard. Metals and chlorides were determined volumetrically’2 and gravimetrically,‘3 respectively. The IR spectra (4000-200 cm-‘) were recorded as CsCl discs on a PerkinElmer 62 1 spectrophotometer. The electronic spectra in DMSO were recorded on a Pye-Unicam 8800 spectrophotometer at room temperature. EPR spectra were recorded on a Jeol JES RE2X EPR spectrometer. The electrical conductivities of lop3 M solution in DMSO were obtained on a Systronic Type 302 conductivity bridge equilibrated at 25 + 0.1°C. Magnetic susceptibility measurements were carried out using a Faraday balance at 25°C.
RESULTS AND DISCUSSION The molecular formulae of the ‘complexes [ML&l&-[ML,Cld or [ML’, Cl,]-[ML;&] have been assigned on the basis of the results of their elemental analyses and the molecular ion peaks in the mass spectra (Table 1). All mass spectra showed molecular ion peaks for the 1: 1 metal-to-ligand stoichiometry with no further peaks above them. A preliminary identification of the metal complexes was made on the basis of their IR spectra, which exhibited no bands characteristic of free primary amine, thus supporting the proposed macrocyclic skeleton (Scheme 1). The IR spectra of all the complexes (Table 2) show a new strong intensity band in the 1590-1610 cm-’ region, which may reasonably be assigned to the imine function [v(eN)] of the macrocyclic system. However, its position is negatively shifted (15-25 cm-‘) when compared with that reported for the uncoordinated imine function in polyaza macrocyclic moieties, indicating coordination via
L~‘A~IX=(C!H&R’~CE~ Ll’ ll X=(CIi&&R’=C$& X=(CH&R’=CH3 4 Li n X=(CEi~3;R’=C$Q L3 ” X=C+gQ ;R’=cH3 X=C.$-& ;R’=C$& w ”
n
Scheme 1.
Complexes of diamidediimine
2321
macrocycles
Table 1. Yield, colour, melting point, elemental analysis and molecular ion peak from the mass spectra and molar conductivity values of the compounds
Compound
[FeWld
Yield
Colour
Melting point (“C)
45
Reddish brown
245
[FeL; Cl*]
50
Reddish brown
228
[FeLKlJ
50
Reddish brown
190
[FeLzC12]
47
Reddish brown
180
[FeL,ClJ
43
Red
275
[FeL;ClJ
48
Red
155
[cow1*1 [COL; Cl*]
[C&~~,l [CoL;Cl*] [CoL,ClJ [coL;cl,]
K=,c1*1 [CUL; CIJ [CuL,ClJ [cuL;cI,] [CuL,ClJ [cuL;cl,] [ZnL,ClJ [ZnL; Cl,]
51 50 53 51 50 48 61 63 65 60 67 61 40 43
Light pink Light pink Light pink Light pink Dark pink Dark pink Green Green Green Green Green Green Colourless Colourless
128 122 149 138 165 157 100 105 120 125 120 130 160 185
W&CL1
44
Colourless
180
[ZnL;Cl,]
47
Colourless
190
]ZnLKU
45
Colourless
180
[ZnL; Cl,]
50
c010ur1ess
165
M 14.8 (14.7) 14.9 (14.7) 13.9 (13.8) 13.8 (13.8) 12.0 (11.8) 11.9 (11.8) 15.6 (15.4) 15.4 (15.4) 14.5 (14.4) 14.4 (14.4) 12.5 (12.3) 12.5 (12.3) 16.5 (16.4) 16.6 (16.4) 15.1 (15.3) 15.2 (15.3) 13.0 (13.2) 13.1 (13.2) 16.4 (16.8) 16.7 (16.8) 15.5 (15.7) 15.6 (15.7) 13.7 (13.5) 13.3 (13.5)
Found (Caic) (%) Cl C H 18.6 (18.7) 18.5 (18.7) 17.4 (17.6) 17.7 (17.6) 15.1 (15.0) 14.9 (15.0) 18.8 (18.6) 18.7 (18.6) 17.5 (17.3) 17.5 (17.3) 14.6 (14.8) 14.8 (14.8) 18.7 (18.4) 18.2 (18.4) 17.3 (17.1) 17.4 (17.1) 14.5 (14.7) 14.9 (14.7) 18.4 (18.3) 18.3 (18.3) 17.2 (17.0) 17.2 (17.0) 14.5 (14.6) 14.5 (14.6)
37.8 (38.0) 38.1 (38.0) 41.4 (41.6) 41.5 (41.6) 50.3 (50.5) 50.4 (50.5) 37.5 (37.7) 37.5 (37.7) 41.3 (41.0) 40.8 (41.0) 50.5 (50.2) 50.1 (50.2) 37.2 (37.3) 37.4 (37.3)
:::,
N 15.0 (14.8) 14.6 (14.8) 13.6 (13.9) 13.8 (13.9) 11.9 (11.8) 11.8 (11.8) 14.6 (14.7) 14.9 (14.7) 13.7 (13.7) 13.5 (13.7) 11.5 (11.7) 11.8 (11.7) 14.7 (14.5) 14.4 (14.5) 13.5 (13.5) 13.7 (13.5) 11.9 (11.6) 11.8 (11.6) 14.3 (14.4) 14.7 (14.4) 13.7 (13.4) 13.5 (13.4) 11.4 (11.6) 11.6 (11.6)
(E) (G) (Z) 4.3 (4.2) (E) :::, ::;, & (E) (E) (E) (E) :::)
(E)
(z::)
(E) 49.8 (49.7) 49.6 (49.7) 37.0 (37.1) 37.4 (37.1) 40.1 (40.3) 40.5 (40.3) 49.9 (49.5) 49.6 (49.5)
(E) (E) (E) :::) :::, 5.8 (5.8) 5.7 (5.8) (E) (E)
(m/z) Found (Calc) 376 (378.8) 377 (378.8) 404 (403.8)
Molar conductivity (cm’ 0-l mol-‘) 11 13 10 17
(Ei.8) 471 (474.8) 473 (474.8) 380 (381.9) 383 (381.9)
21 15 12 19 12
(E.9) 11 (E.2) 476 (477.9) 473 (477.9) 384 (386.5) 385 (386.5) 413 (414.5)
13 21 22 29 14 17
$5) 480 (482.5) 481 (482.5) 386 (388.4) 385 (388.4) 415 (416.4) 413 (416.4) 481 (484.4) 484 (484.4)
11 12 15 16 10 14 15 12
2322
M. SHAKIR et al. Table 2. IR vibrational frequencies (cm-‘)
Compounds
[FeWU
[FeL’, ClJ
[FeWAl [FeL;Cl,]
W-d4
[FeL;Cl,]
KOLCW [COL; ClJ
w-&~*l [coL;cl,]
Paw
[coL;cl,]
~CuLCW [CUL; ClJ
wa*l
[cuL;cl,]
~C~bCl21 [CUL; Cl*] [ZnL,ClJ [ZnL; Cl,]
[ZnLGl [ZnLzC1,]
tZnLCL1 [ZnL;Cl,]
v(NH)
v(CH)
v(C=N)
3250 3260 3255 3245 3230 3255 3260 3240 3250 3230 3245 3250 3260 3245 3250 3255 3230 3240 3245 3230 3255 3240 3260 3250
2885 2880 2875 2890 2910 2900 2925 2895 2910 2915 2880 2920 2875 2890 2910 2895 2915 2930 2890 2915 2920 2910 2890 2900
1595 1590 1610 1605 1610 1605 1600 1605 1600 1595 1605 1600 1610 1600 1605 1595 1600 1610 1590 1595 1605 1595 1600 1590
I 680 675 700 695 710 690 1695 1700 1690 1695 1720 1710 1700 1695 1675 1690 1710 1700 1720 1690 1695 1715 1700 1705
the nitrogen atoms 14*15of the ligand. However, the bands in the region 168&1720, 1495-1510, 12301270 and 65&670 cm-’ may be assigned to amide I [v(C=O)], amide II [v(C-N) +6(N-H)], amide III [6(N-H)] and amide IV [&c---O)] vibrations, respectively.16 A single sharp band observed for all the complexes in the region 3230-3260 cm-’ may possibly arise from a secondary amine, v(NH), although its position has been found to be lower by
of the compounds
Amide bands II III
IV
6(CH)
v(M-N)
1500 1510 1505 1510 1510 1500 1495 1495 1510 1505 1500 1495 1505 1510 1500 1495 1510 1505 1495 1510 1495 1510 1505 1500
660 670 655 650 670 660 650 660 650 655 665 660 650 660 655 670 660 650 665 650 655 670 660 660
1425 1420 1425 1400 1420 1435 1425 1420 1450 1440 1415 1440 1420 1400 1450 1440 1425 1420 1435 1415 1440 1450 1415 1425
325 340 320 340 355 345 365 360 325 330 345 350 345 360 355 320 340 365 330 340 325 320 350 355
1240 1245 1230 1255 1240 1270 1250 1260 1255 1265 1235 1245 1245 1230 1240 1260 1245 1230 1265 1250 1270 1235 1245 1260
CH3
[ZnWAI
1.62(s) 1.60(s) 1.63(s) 1.69(s) 1.80(s) 1.82(s)
[ZnL; Cl,]
~ZnJJ-AI [ZnL;Cl,] [ZnLGl [ZnL;Cl,]
-CH,-N 3.12(s) 3.14(s) 3.15(m) 3.16(m) -
285 280 280 290 285 290 285 280 290 285 280 290 290 280 285 290 280 285 285 290 285 280 290 290
40-60 cm-’ than the analogous metal-free tetraaza ligands.” This suggests that the amide nitrogens take part in coordination to the metal ions, which has been further confirmed by the appearance of bands in the 320-365 cm-’ region in all the complexes corresponding to v(M-N) vibrations. The absorption bands in the 2850-2950 and 1400-1450 cm-’ regions observed in all the complexes may reasonably correspond to CH stretching and
Table 3. ‘H NMR spectroscopic data of the compounds” Compound
v(M-Cl)
C-CH,-C 2.20(s) 2.10(s) 2.22(s) 2.25(s) 2.31(s) 2.28(s)
“Chemical shifts (d/ppm) with multiplicities in parentheses.
-CO-NH 8.33(s) 8.40(s) 8.38(s) 8.41 (s) 8.34(s) 8.30(s)
Ring protons 7.70(m) 7.51(m)
Complexes of diamidediimine
2323
macrocycles
Table 4. pH, ligand field bands observed in the electronic spectra (cm-‘) and their assignments of the compounds Peti
Compounds
(B.M.)
[FeLC121
5.31
[FeL’, Cl*] [FeLK&] [FeL;Cl,]
FW31 [FeL;Cl,J
5.39 5.41 5.53 5.51 5.55
v&c1*1
4.54
[COL; Cl, ]
4.54
PWLI
4.61
[coL;cl,]
4.63
[coLcu
4.61
[coL;cl,]
4.55
DGW
1.73
[CuL{ Cl,]
P&w [CuL;CI,] [CuW121 [CUL; Cl,]
1.75
1.74
1.74
1.73
1.91
Band position (cm-‘) 11,350 33,500 11,510 33,300 11,210 33,410 11,400 32,400 11,850 34,400 11,900 34,350 13,540 21,830 35,200 13,610 21,700 35,560 13,510 22,200 35,340 14,450 21,950 35,600 14,420 22,150 35,290 14,300 22,050 35,550 15,350 18,400 35,100 15,280 18,700 35,200 16,600 18,850 35,250 15,500 19,000 35,200 16,620 18,500 35,350 15,090 18,200 35,200
Assignments ‘Egts Tz9
Charge transfer 5E,--’ Tzg
Charge transfer ’ Egc5 Tzg
Charge transfer ‘E,t5 T,,
Charge transfer ‘Egt5 Tzg
Charge transfer ’ Eg-’ Tzg
Charge transfer 4&,(F)+-4T~,(F) 4T,,(P)+4T,,(F) Charge transfer 4&,(F)+4T,,(F) 4T~,(P)+4T,,(F) Charge transfer 4&,(F)-4T~,(F) 4T~,(P)+4T,,(F) Charge transfer 4-&,(F)+4T,,(F) 4T&‘)+4T,,(F) Charge transfer 4&,(F)-4T,,(F) 4T,,(W-4T,,(F) Charge transfer 4&,(F)+4T~,(F) 4T&‘)+4T~,(F) Charge transfer 2Q-2B~, 2Eg+2B,,
Charge transfer 2&/--2B,, ‘E,cZB,,
Charge transfer 2Bz,+2B,, 2Eg--2B,,
Charge transfer 2Q-2B,, ‘E,+-‘B,,
Charge transfer 2&,+-2B~, ‘E,e’B,,
Charge transfer 2&,+2B,, 2Eg+-2B,,
Charge transfer
2324
M. SHAKIR et al.
CH bending vibrational modes. However, a medium intensity band at 280-290 cm-’ may unambiguously be assigned for the M-Cl stretching mode. The EPR spectra of the polycrystalline Cu” macrocyclic complexes were recorded at room temperature and their g,, and g1 values have been calculated. The values of g,, and g1 have been used to distinguish” unambiguously between dxz_,,z and the d,z ground states. For example, for the d,z_g ground state the EPR spectrum should give g,, > g,_ > 2.02 in most cases, whilst a dzz ground state usually gives a spectrum with g1 > g,, N 2.0. The tetraazamacrocyclic copper(I1) complexes studied here do not show any hyperfine splitting, but gave only a single signal for which gll and g1 values appeared in the regions 2.24-2.30 and 2.092.15, respectively. These observations are characteristic*“*’ of axially distorted octahedral copper(I1) complexes in which the unpaired electron is present in the d,z_g orbital. In an axial symmetry the g values are related by the expression G = @,,- 2)/@, - 2), which measures the exchange interaction between copper centres in the polycrystalline solid ;**if G > 4 exchange interaction is negligible and G < 4 indicates considerable exchange interaction in the solid complexes. The calculated G values appeared in the range 1.66-2.66. The gay values were calculated according to the relation gav = $@,,+gJ and gave values in the range 2.23 kO.07, which are in agreement with an orbitally non-degenerate ground state.23 The ‘H NMR spectra of the zinc complexes (Table 3) gave singlets at 1.60-1.82 and 2.1G2.31 ppm, corresponding” to CH3(6H) protons and CH2(4H) protons of the alkyl acetoacetate, respectively. However, the ‘H NMR spectra of the complexes [ML,ClJ and [ML;Cl,] show a multiplet in the region 7.51-7.70 ppm, corresponding to the phenyl ring protons (8H). The ‘H NMR spectra of all the complexes show a broad signal at 8.23-8.41 ppm and can be assigned” to amide protons (2H), whilst the spectra of the complexes [ML1C12] and [ML’,Cl,] show a singlet at 3.12-3.16 ppm. A multiplet for the complexes [ML,C12] and [ML;Cl,] shown at 3.08-3.16 ppm corresponds to CH2 (8H) protons14 adjacent to nitrogen while the middle CH2 (4H) protons of the propane chain of the complexes [ML,Cl,] and [ML;Cl,] give a multiplet at 2.052.09 ppm. However, the spectra of all the complexes do not show any signal corresponding to free primary amine protons. The observed low molar conductivities recorded in DMSO indicate that these are non-electrolytes in nature. The overall geometries of these macrocycles
have been deduced on the basis of the observed values of the magnetic moments and the band positions in the electronic spectra. The observed magnetic moments pea (B.M.) (Table 4) recorded at room temperature correspond to high-spin d6 and d’ systems, consistent2~2s with the octahedral environment around iron(I1) and cobalt(I1). The electronic spectra of iron(I1) complexes exhibit a weak intensity band at ca 11,210-l 1,900 cm-‘, which may reasonably be assigned to ‘T2,+ ‘E, (Table 4) consistent26,27with an octahedral environment around the iron(I1) ion. However, the electronic spectra of the cobalt complexes show two ligand field bands appearing in the 13,510-14,450 and 21,700-22,200 cm-’ regions which may reasonably29 correspond to 4T,, (F)--r4A2, (F) and 4T1, (F) -+4T,, (P) transitions, respectively. The band corresponding to the transition 4T1, (F) -4T2s (F) expected to appear below the 8500 cm-’ range could not be recorded for these complexes as it lies beyond the range of the instrument. The electronic spectra of the copper complexes show a broad band (Table 4) maxima at ca 18,20019,000 cm-’ with a shoulder on the low energy side at ca 15,280-16,620 cm-‘, which may unambiguously be assigned to *B1,+ ‘E, and *B1,-+ ‘B, transitions respectively, corresponding to distorted octahedral geometry around the metal ion.30 The magnetic moment values again confirm the above proposed geometry. All the complexes exhibit strong absorptions around 30,700 cm-‘, which may be associated with the intraligand charge-transfer involving the imine functions.3’ authors thank Chairman, Department of Chemistry and CDRI, Lucknow, for providing research and laboratory facilities. Mr Saji PV is thankful to CSIR, New Delhi, for financial support to this work.
Acknowledgements-The
REFERENCES M. N. Hughes, in Inorganic Chemistry of Biological Processes, 2nd edn. Wiley, New York (198 1).
L. Casella, M. Gullotti, L. D. Gioia, E. Monzani and F. Chillemi, .I. Chem. Sot., Dalton Trans. 1991,2945. K. R. Adam, M. Antolovich, D. S. Baldwin, L. G. Brgden, P. A. Duckworth, L. F. Lindoy, A. Bashall, M. McPartlin and P. A. Tasker J. Chem. Sot., Dalton Trans. 1992, 1869. 4. G. A. Melson, Coordination Chemistry of Macrocyclic Compounds, p. 108. Plenum Press, New York
(1979). 5. M. de S. Healey and A. J. Rest, Adv. Znorg. Chem. Radiochem. 1978, 21, 1. 6. D. H. Busch, Helv. Chim. Acta 1976, 174; Recent
Complexes of diamidediimine Chem. Prog. 1964, 25, 107 ; C. J. Hipp and D. H. Busch. AC’S Monoar. 1978,174,220. 7. L. F. Lindoy, The-Chemistry of Macrocyclic L&and Complexes. Cambridge University Press, Cambridge (1989). 8. E. Kimura, M. Kodama, R. Machida and K. Ishixu, Inorg. Chem. 1982,21, 595. 9. M. Shakir, P. S. Hameed and S. P. Varkey, Polyhedron 1994, in press. 10. M. Shakir, S. P. Varkey and P. S. Hameed, J. Chem. Res. 1993, 11,442. 11. M. Shakir, S. P. Varkey and P. S. Hameed, PoZyhedron 1994,13,1355. 12. C. N. Reilly, R. W. Schmid and F. A. Sadak, J. Chem. Educ. 1959,36,619. 13. A. I. Vogel, Text Book of Quantitative Inorganic Analysis, p. 433. Longmans, London (1961). 14. M. G. B. Drew, F. S. Esho and S. M. Nelson, J. Chem. Sot., Dalton Trans. 1983, 1653. 15. D. E. Fenton, B. P. Murphy, A. J. Leong, L. F. Lindoy, A. Basheel and M. McPartlin, J. Chem. Sot., Dalton Trans. 1987,2543. 16. J. Bould and B. J. Brisdon, Znorg. Chim. Acta 1976, 19, 159. 17. D. H. Cook and D. E. Fenton, Znorg. Chim. Actu 1977, 25, L95. 18. N. S. Biradar and V. S. Kulkami, J. Znorg. Nucl. Chem. 1971,33,2451.
macrocycles
2325
19. M. C. Jam, A. K. Srivastava and P. C. Jain, Znorg. Chim. Actu 1977,X$ 199. 20. K. G. K. Sundar and K. J. Rao, J. Non Cryst. Solids 1982, SO, 137. 21. B. J. Hathaway and D. E. Billing, Coord. Chem. Rev. 1970,5, 143. 22. I. M. Procter, B. J. Hathaway and P. Nicholls, J. Chem. Sot. A 1968, 1678. 23. B. N. Figgis, Introduction to Ligand Fields, p. 296. Interscience, New York (1966). 24. P. R. Shukla, M. Bhatt and M. C. Sharma, J. Znd. Chem. Sot. 1989,66,192. 25. T. C. Woon and D. P. Fairlie, Znorg. Chem. 1992,31, 4069. 26. J. Reedijk, W. L. Driessen and W. L. Groeneveld, Rec. Trav. Chim. 1969,88, 1095. 27. J. Reedijk, P. W. N. M. Van Leenwen and W. L. Groeneveld, Rec. Trav. Chim. 1968,87, 129. 28. M. J. Bagley, D. Nicholls and B. A. Warburton, J. Chem. Sot. A 1970,2694. 29. D. A. Baldwin, A. B. P. Lever and R. V. Parish, Znorg. Chem. 1969,8, 107. 30. A. B. P. Lever, Inorganic Electronic Spectroscopy. Elsevier, Amsterdam (1968). 31. A. M. Tait and D. H. Busch, Znorg. Chem. 1976,15, 197.
0277-5387(W)EOO!W-X
Polyhedron Vol. 13, No. 15116, pp. 2319-2325, 1994 Ekwier science Ltd Printed in Great Britain 0277-5387p4 $7.00+0.00
TEMPLATE SYNTHESIS OF IRON@), COBALT(D), COPPER@) and ZINC@) COMPLEXES OF DIAMIDEDIIMINE MACROCYCLES MOHAMMAD
SHAKIR,*
SAJI P. VARKEY, FARHA FIRDAUS and HAMEED
P. SHAHUL
Division of Inorganic Chemistry, Department of Chemistry, Aligarh Muslim University, Aligarh 202 002, India (Received
17 January 1994 ; accepted 1 March 1994)
Abstract-A
series of iron( cobalt(II), copper(I1) and zinc(I1) complexes containing tetraazamacrocyclic ligands have been prepared by the condensation of 1,2-diaminoethane, 1,3-diaminopropane and ortho-phenylene diamine with methyl acetoacetate or ethyl acetoacetate in the presence of iron( cobalt(II), copper(I1) and zinc(I1) salts at room temperature. The structure and bonding of macrocyclic ligands have been studied from elemental analysis, magnetic susceptibility measurements, IR, ‘H NMR, mass, EPR and electronic spectra of the complexes. The stereochemistry around the metal ions is octahedral in which four of the coordination sites are occupied by the nitrogens of the macrocyclic ligand and the remaining octahedral positions are occupied by two chlorines.
The design and synthesis of polyazamacrocycles have attracted increasing interest in recent years for the possible relevance of these compounds as model’*2 ligands for metal enzymes and metal proteins as metal-ion selective ligands. Synthesis of organic substrates that preferentially interact with particular metal ions is of fundamental importance to many areas of chemistry.3 Condensation reactions between dicarbonyls and primary diamines have played an important role in the development of synthetic macrocyclic ligands which have been proved to be a fruitful source of imino macrocycles.4,21Usually such syntheses were carried out in the presence of a suitable metal ion which serves to direct the steric course of the reaction preferentially towards cyclic rather than oligomeric or polymeric products.4d Of the polyazamacrocycles, the tetraaza group has been the most intensively studied because of its great biological importance. Relative to their open-chain analogues, macrocyclic ligands have further stereochemical contraints associated with their cyclic nature which may influence their
*Author to whom correspondence should be addressed.
potential for metal ion recognition.7 For macrocycles incorporating rigid or semi-rigid cavities, recognition (and hence discrimination) may be associated with a close match or otherwise of the radius of the metal ion for the cavity.3 Kimura and co-workers have reported’ a series of diamide macrocycles and their applications. Recently we have reported9,“‘*” the synthesis and characterization of tetraazamacrocyclic complexes bearing the polyamide group and dithiadiazamacrocyclic complexes. Herein we report the synthesis and characterization of diamidediimine tetraazamacrocyclic complexes, [ML,Cl+ [ML,ClJ and wL’,Cl,]-[ML;Cl,] [M = Fe”, Co”, Cu” and Zn”), which resulted from the condensation of methylacetoacetate or ethylacetoacetate and diamines in the presence of metal salts EXPERIMENTAL
The chemicals, methyl acetoacetate, ethyl acetoacetate, 1,3-diaminopropane, 1,Zdiaminoethane and ortho-phenylene diamine (all E. Merck) were used as received. FeCl, * 6H2O, CoC12* 6H2O,
2319
2320
M. SHAKIR et al.
CuCl, * 2Hz0 and ZnCl, (BDH) were commercially pure samples and were dehydrated with acetic anhydride. All the solvents were dried before use. Preparation of dichloro(5,12-dioxa-l,lCdimethyl1,4,&l 1-tetraazacyclotetradeca-1 ,&diene) metaZ(II), [ML&l or [ML’, Clz] (M = Fe”, Co’i, Cu” or Zn”)
A methanolic solution (50 cm3) of ethylene diamine (20 mmol) was added dropwise with stirring to a methanolic solution (50 cm3) of the anhydrous metal chloride (10 mmol). After the addition of all the diamine, the contents were stirred for 1 h, followed by the addition of a methanolic solution (50 cm3) of methyl acetoacetate or ethyl acetoacetate (20 mmol) and stirred for a further 16 h at room temperature, resulting in the formation of the macrocyclic complexes [ML,C12] or [ML’, Cl*] (M = Fe”, Co”, Cu” or Zn”). The microcrystalline products thus formed were filtered, washed several times with methanol and dried in uacuo. All the experiments were carried out under dry nitrogen. Preparation
of dichloro(6,14-dioxa-8,16-dimethyl-
1,5,9,13-tetraazacyclohexadeca- 1,9-diene) metal(I1) and dichloro(2,3 : 9,10-dibenzo-5,12-dioxa-7,14-d& methyl - 1,4,&l 1 - tetraazacyclotetradeca - 1,8 - diene) metal(I1) [ML,Cld or [ML;Cl,] and [ML,ClJ or [ML;Cl,] (M = Fe”, Co”, Cu” or Zn”)
These compounds were prepared and isolated by the same procedure as described above. Here 1,3propanediamine and ortho-phenylenediamines were employed instead of ethylenediamine. Elemental analyses for C, H, N and mass spectra (JMSD-300) were obtained from the Microanalytical Laboratory of CDRI, Lucknow, India. ‘H NMR spectra were determined in DMSO-d6
using a Bruker AC 200E NMR spectrometer with Me,Si as an internal standard. Metals and chlorides were determined volumetrically’2 and gravimetrically,‘3 respectively. The IR spectra (4000-200 cm-‘) were recorded as CsCl discs on a PerkinElmer 62 1 spectrophotometer. The electronic spectra in DMSO were recorded on a Pye-Unicam 8800 spectrophotometer at room temperature. EPR spectra were recorded on a Jeol JES RE2X EPR spectrometer. The electrical conductivities of lop3 M solution in DMSO were obtained on a Systronic Type 302 conductivity bridge equilibrated at 25 + 0.1°C. Magnetic susceptibility measurements were carried out using a Faraday balance at 25°C.
RESULTS AND DISCUSSION The molecular formulae of the ‘complexes [ML&l&-[ML,Cld or [ML’, Cl,]-[ML;&] have been assigned on the basis of the results of their elemental analyses and the molecular ion peaks in the mass spectra (Table 1). All mass spectra showed molecular ion peaks for the 1: 1 metal-to-ligand stoichiometry with no further peaks above them. A preliminary identification of the metal complexes was made on the basis of their IR spectra, which exhibited no bands characteristic of free primary amine, thus supporting the proposed macrocyclic skeleton (Scheme 1). The IR spectra of all the complexes (Table 2) show a new strong intensity band in the 1590-1610 cm-’ region, which may reasonably be assigned to the imine function [v(eN)] of the macrocyclic system. However, its position is negatively shifted (15-25 cm-‘) when compared with that reported for the uncoordinated imine function in polyaza macrocyclic moieties, indicating coordination via
L~‘A~IX=(C!H&R’~CE~ Ll’ ll X=(CIi&&R’=C$& X=(CH&R’=CH3 4 Li n X=(CEi~3;R’=C$Q L3 ” X=C+gQ ;R’=cH3 X=C.$-& ;R’=C$& w ”
n
Scheme 1.
Complexes of diamidediimine
2321
macrocycles
Table 1. Yield, colour, melting point, elemental analysis and molecular ion peak from the mass spectra and molar conductivity values of the compounds
Compound
[FeWld
Yield
Colour
Melting point (“C)
45
Reddish brown
245
[FeL; Cl*]
50
Reddish brown
228
[FeLKlJ
50
Reddish brown
190
[FeLzC12]
47
Reddish brown
180
[FeL,ClJ
43
Red
275
[FeL;ClJ
48
Red
155
[cow1*1 [COL; Cl*]
[C&~~,l [CoL;Cl*] [CoL,ClJ [coL;cl,]
K=,c1*1 [CUL; CIJ [CuL,ClJ [cuL;cI,] [CuL,ClJ [cuL;cl,] [ZnL,ClJ [ZnL; Cl,]
51 50 53 51 50 48 61 63 65 60 67 61 40 43
Light pink Light pink Light pink Light pink Dark pink Dark pink Green Green Green Green Green Green Colourless Colourless
128 122 149 138 165 157 100 105 120 125 120 130 160 185
W&CL1
44
Colourless
180
[ZnL;Cl,]
47
Colourless
190
]ZnLKU
45
Colourless
180
[ZnL; Cl,]
50
c010ur1ess
165
M 14.8 (14.7) 14.9 (14.7) 13.9 (13.8) 13.8 (13.8) 12.0 (11.8) 11.9 (11.8) 15.6 (15.4) 15.4 (15.4) 14.5 (14.4) 14.4 (14.4) 12.5 (12.3) 12.5 (12.3) 16.5 (16.4) 16.6 (16.4) 15.1 (15.3) 15.2 (15.3) 13.0 (13.2) 13.1 (13.2) 16.4 (16.8) 16.7 (16.8) 15.5 (15.7) 15.6 (15.7) 13.7 (13.5) 13.3 (13.5)
Found (Caic) (%) Cl C H 18.6 (18.7) 18.5 (18.7) 17.4 (17.6) 17.7 (17.6) 15.1 (15.0) 14.9 (15.0) 18.8 (18.6) 18.7 (18.6) 17.5 (17.3) 17.5 (17.3) 14.6 (14.8) 14.8 (14.8) 18.7 (18.4) 18.2 (18.4) 17.3 (17.1) 17.4 (17.1) 14.5 (14.7) 14.9 (14.7) 18.4 (18.3) 18.3 (18.3) 17.2 (17.0) 17.2 (17.0) 14.5 (14.6) 14.5 (14.6)
37.8 (38.0) 38.1 (38.0) 41.4 (41.6) 41.5 (41.6) 50.3 (50.5) 50.4 (50.5) 37.5 (37.7) 37.5 (37.7) 41.3 (41.0) 40.8 (41.0) 50.5 (50.2) 50.1 (50.2) 37.2 (37.3) 37.4 (37.3)
:::,
N 15.0 (14.8) 14.6 (14.8) 13.6 (13.9) 13.8 (13.9) 11.9 (11.8) 11.8 (11.8) 14.6 (14.7) 14.9 (14.7) 13.7 (13.7) 13.5 (13.7) 11.5 (11.7) 11.8 (11.7) 14.7 (14.5) 14.4 (14.5) 13.5 (13.5) 13.7 (13.5) 11.9 (11.6) 11.8 (11.6) 14.3 (14.4) 14.7 (14.4) 13.7 (13.4) 13.5 (13.4) 11.4 (11.6) 11.6 (11.6)
(E) (G) (Z) 4.3 (4.2) (E) :::, ::;, & (E) (E) (E) (E) :::)
(E)
(z::)
(E) 49.8 (49.7) 49.6 (49.7) 37.0 (37.1) 37.4 (37.1) 40.1 (40.3) 40.5 (40.3) 49.9 (49.5) 49.6 (49.5)
(E) (E) (E) :::) :::, 5.8 (5.8) 5.7 (5.8) (E) (E)
(m/z) Found (Calc) 376 (378.8) 377 (378.8) 404 (403.8)
Molar conductivity (cm’ 0-l mol-‘) 11 13 10 17
(Ei.8) 471 (474.8) 473 (474.8) 380 (381.9) 383 (381.9)
21 15 12 19 12
(E.9) 11 (E.2) 476 (477.9) 473 (477.9) 384 (386.5) 385 (386.5) 413 (414.5)
13 21 22 29 14 17
$5) 480 (482.5) 481 (482.5) 386 (388.4) 385 (388.4) 415 (416.4) 413 (416.4) 481 (484.4) 484 (484.4)
11 12 15 16 10 14 15 12
2322
M. SHAKIR et al. Table 2. IR vibrational frequencies (cm-‘)
Compounds
[FeWU
[FeL’, ClJ
[FeWAl [FeL;Cl,]
W-d4
[FeL;Cl,]
KOLCW [COL; ClJ
w-&~*l [coL;cl,]
Paw
[coL;cl,]
~CuLCW [CUL; ClJ
wa*l
[cuL;cl,]
~C~bCl21 [CUL; Cl*] [ZnL,ClJ [ZnL; Cl,]
[ZnLGl [ZnLzC1,]
tZnLCL1 [ZnL;Cl,]
v(NH)
v(CH)
v(C=N)
3250 3260 3255 3245 3230 3255 3260 3240 3250 3230 3245 3250 3260 3245 3250 3255 3230 3240 3245 3230 3255 3240 3260 3250
2885 2880 2875 2890 2910 2900 2925 2895 2910 2915 2880 2920 2875 2890 2910 2895 2915 2930 2890 2915 2920 2910 2890 2900
1595 1590 1610 1605 1610 1605 1600 1605 1600 1595 1605 1600 1610 1600 1605 1595 1600 1610 1590 1595 1605 1595 1600 1590
I 680 675 700 695 710 690 1695 1700 1690 1695 1720 1710 1700 1695 1675 1690 1710 1700 1720 1690 1695 1715 1700 1705
the nitrogen atoms 14*15of the ligand. However, the bands in the region 168&1720, 1495-1510, 12301270 and 65&670 cm-’ may be assigned to amide I [v(C=O)], amide II [v(C-N) +6(N-H)], amide III [6(N-H)] and amide IV [&c---O)] vibrations, respectively.16 A single sharp band observed for all the complexes in the region 3230-3260 cm-’ may possibly arise from a secondary amine, v(NH), although its position has been found to be lower by
of the compounds
Amide bands II III
IV
6(CH)
v(M-N)
1500 1510 1505 1510 1510 1500 1495 1495 1510 1505 1500 1495 1505 1510 1500 1495 1510 1505 1495 1510 1495 1510 1505 1500
660 670 655 650 670 660 650 660 650 655 665 660 650 660 655 670 660 650 665 650 655 670 660 660
1425 1420 1425 1400 1420 1435 1425 1420 1450 1440 1415 1440 1420 1400 1450 1440 1425 1420 1435 1415 1440 1450 1415 1425
325 340 320 340 355 345 365 360 325 330 345 350 345 360 355 320 340 365 330 340 325 320 350 355
1240 1245 1230 1255 1240 1270 1250 1260 1255 1265 1235 1245 1245 1230 1240 1260 1245 1230 1265 1250 1270 1235 1245 1260
CH3
[ZnWAI
1.62(s) 1.60(s) 1.63(s) 1.69(s) 1.80(s) 1.82(s)
[ZnL; Cl,]
~ZnJJ-AI [ZnL;Cl,] [ZnLGl [ZnL;Cl,]
-CH,-N 3.12(s) 3.14(s) 3.15(m) 3.16(m) -
285 280 280 290 285 290 285 280 290 285 280 290 290 280 285 290 280 285 285 290 285 280 290 290
40-60 cm-’ than the analogous metal-free tetraaza ligands.” This suggests that the amide nitrogens take part in coordination to the metal ions, which has been further confirmed by the appearance of bands in the 320-365 cm-’ region in all the complexes corresponding to v(M-N) vibrations. The absorption bands in the 2850-2950 and 1400-1450 cm-’ regions observed in all the complexes may reasonably correspond to CH stretching and
Table 3. ‘H NMR spectroscopic data of the compounds” Compound
v(M-Cl)
C-CH,-C 2.20(s) 2.10(s) 2.22(s) 2.25(s) 2.31(s) 2.28(s)
“Chemical shifts (d/ppm) with multiplicities in parentheses.
-CO-NH 8.33(s) 8.40(s) 8.38(s) 8.41 (s) 8.34(s) 8.30(s)
Ring protons 7.70(m) 7.51(m)
Complexes of diamidediimine
2323
macrocycles
Table 4. pH, ligand field bands observed in the electronic spectra (cm-‘) and their assignments of the compounds Peti
Compounds
(B.M.)
[FeLC121
5.31
[FeL’, Cl*] [FeLK&] [FeL;Cl,]
FW31 [FeL;Cl,J
5.39 5.41 5.53 5.51 5.55
v&c1*1
4.54
[COL; Cl, ]
4.54
PWLI
4.61
[coL;cl,]
4.63
[coLcu
4.61
[coL;cl,]
4.55
DGW
1.73
[CuL{ Cl,]
P&w [CuL;CI,] [CuW121 [CUL; Cl,]
1.75
1.74
1.74
1.73
1.91
Band position (cm-‘) 11,350 33,500 11,510 33,300 11,210 33,410 11,400 32,400 11,850 34,400 11,900 34,350 13,540 21,830 35,200 13,610 21,700 35,560 13,510 22,200 35,340 14,450 21,950 35,600 14,420 22,150 35,290 14,300 22,050 35,550 15,350 18,400 35,100 15,280 18,700 35,200 16,600 18,850 35,250 15,500 19,000 35,200 16,620 18,500 35,350 15,090 18,200 35,200
Assignments ‘Egts Tz9
Charge transfer 5E,--’ Tzg
Charge transfer ’ Egc5 Tzg
Charge transfer ‘E,t5 T,,
Charge transfer ‘Egt5 Tzg
Charge transfer ’ Eg-’ Tzg
Charge transfer 4&,(F)+-4T~,(F) 4T,,(P)+4T,,(F) Charge transfer 4&,(F)+4T,,(F) 4T~,(P)+4T,,(F) Charge transfer 4&,(F)-4T~,(F) 4T~,(P)+4T,,(F) Charge transfer 4-&,(F)+4T,,(F) 4T&‘)+4T,,(F) Charge transfer 4&,(F)-4T,,(F) 4T,,(W-4T,,(F) Charge transfer 4&,(F)+4T~,(F) 4T&‘)+4T~,(F) Charge transfer 2Q-2B~, 2Eg+2B,,
Charge transfer 2&/--2B,, ‘E,cZB,,
Charge transfer 2Bz,+2B,, 2Eg--2B,,
Charge transfer 2Q-2B,, ‘E,+-‘B,,
Charge transfer 2&,+-2B~, ‘E,e’B,,
Charge transfer 2&,+2B,, 2Eg+-2B,,
Charge transfer
2324
M. SHAKIR et al.
CH bending vibrational modes. However, a medium intensity band at 280-290 cm-’ may unambiguously be assigned for the M-Cl stretching mode. The EPR spectra of the polycrystalline Cu” macrocyclic complexes were recorded at room temperature and their g,, and g1 values have been calculated. The values of g,, and g1 have been used to distinguish” unambiguously between dxz_,,z and the d,z ground states. For example, for the d,z_g ground state the EPR spectrum should give g,, > g,_ > 2.02 in most cases, whilst a dzz ground state usually gives a spectrum with g1 > g,, N 2.0. The tetraazamacrocyclic copper(I1) complexes studied here do not show any hyperfine splitting, but gave only a single signal for which gll and g1 values appeared in the regions 2.24-2.30 and 2.092.15, respectively. These observations are characteristic*“*’ of axially distorted octahedral copper(I1) complexes in which the unpaired electron is present in the d,z_g orbital. In an axial symmetry the g values are related by the expression G = @,,- 2)/@, - 2), which measures the exchange interaction between copper centres in the polycrystalline solid ;**if G > 4 exchange interaction is negligible and G < 4 indicates considerable exchange interaction in the solid complexes. The calculated G values appeared in the range 1.66-2.66. The gay values were calculated according to the relation gav = $@,,+gJ and gave values in the range 2.23 kO.07, which are in agreement with an orbitally non-degenerate ground state.23 The ‘H NMR spectra of the zinc complexes (Table 3) gave singlets at 1.60-1.82 and 2.1G2.31 ppm, corresponding” to CH3(6H) protons and CH2(4H) protons of the alkyl acetoacetate, respectively. However, the ‘H NMR spectra of the complexes [ML,ClJ and [ML;Cl,] show a multiplet in the region 7.51-7.70 ppm, corresponding to the phenyl ring protons (8H). The ‘H NMR spectra of all the complexes show a broad signal at 8.23-8.41 ppm and can be assigned” to amide protons (2H), whilst the spectra of the complexes [ML1C12] and [ML’,Cl,] show a singlet at 3.12-3.16 ppm. A multiplet for the complexes [ML,C12] and [ML;Cl,] shown at 3.08-3.16 ppm corresponds to CH2 (8H) protons14 adjacent to nitrogen while the middle CH2 (4H) protons of the propane chain of the complexes [ML,Cl,] and [ML;Cl,] give a multiplet at 2.052.09 ppm. However, the spectra of all the complexes do not show any signal corresponding to free primary amine protons. The observed low molar conductivities recorded in DMSO indicate that these are non-electrolytes in nature. The overall geometries of these macrocycles
have been deduced on the basis of the observed values of the magnetic moments and the band positions in the electronic spectra. The observed magnetic moments pea (B.M.) (Table 4) recorded at room temperature correspond to high-spin d6 and d’ systems, consistent2~2s with the octahedral environment around iron(I1) and cobalt(I1). The electronic spectra of iron(I1) complexes exhibit a weak intensity band at ca 11,210-l 1,900 cm-‘, which may reasonably be assigned to ‘T2,+ ‘E, (Table 4) consistent26,27with an octahedral environment around the iron(I1) ion. However, the electronic spectra of the cobalt complexes show two ligand field bands appearing in the 13,510-14,450 and 21,700-22,200 cm-’ regions which may reasonably29 correspond to 4T,, (F)--r4A2, (F) and 4T1, (F) -+4T,, (P) transitions, respectively. The band corresponding to the transition 4T1, (F) -4T2s (F) expected to appear below the 8500 cm-’ range could not be recorded for these complexes as it lies beyond the range of the instrument. The electronic spectra of the copper complexes show a broad band (Table 4) maxima at ca 18,20019,000 cm-’ with a shoulder on the low energy side at ca 15,280-16,620 cm-‘, which may unambiguously be assigned to *B1,+ ‘E, and *B1,-+ ‘B, transitions respectively, corresponding to distorted octahedral geometry around the metal ion.30 The magnetic moment values again confirm the above proposed geometry. All the complexes exhibit strong absorptions around 30,700 cm-‘, which may be associated with the intraligand charge-transfer involving the imine functions.3’ authors thank Chairman, Department of Chemistry and CDRI, Lucknow, for providing research and laboratory facilities. Mr Saji PV is thankful to CSIR, New Delhi, for financial support to this work.
Acknowledgements-The
REFERENCES M. N. Hughes, in Inorganic Chemistry of Biological Processes, 2nd edn. Wiley, New York (198 1).
L. Casella, M. Gullotti, L. D. Gioia, E. Monzani and F. Chillemi, .I. Chem. Sot., Dalton Trans. 1991,2945. K. R. Adam, M. Antolovich, D. S. Baldwin, L. G. Brgden, P. A. Duckworth, L. F. Lindoy, A. Bashall, M. McPartlin and P. A. Tasker J. Chem. Sot., Dalton Trans. 1992, 1869. 4. G. A. Melson, Coordination Chemistry of Macrocyclic Compounds, p. 108. Plenum Press, New York
(1979). 5. M. de S. Healey and A. J. Rest, Adv. Znorg. Chem. Radiochem. 1978, 21, 1. 6. D. H. Busch, Helv. Chim. Acta 1976, 174; Recent
Complexes of diamidediimine Chem. Prog. 1964, 25, 107 ; C. J. Hipp and D. H. Busch. AC’S Monoar. 1978,174,220. 7. L. F. Lindoy, The-Chemistry of Macrocyclic L&and Complexes. Cambridge University Press, Cambridge (1989). 8. E. Kimura, M. Kodama, R. Machida and K. Ishixu, Inorg. Chem. 1982,21, 595. 9. M. Shakir, P. S. Hameed and S. P. Varkey, Polyhedron 1994, in press. 10. M. Shakir, S. P. Varkey and P. S. Hameed, J. Chem. Res. 1993, 11,442. 11. M. Shakir, S. P. Varkey and P. S. Hameed, PoZyhedron 1994,13,1355. 12. C. N. Reilly, R. W. Schmid and F. A. Sadak, J. Chem. Educ. 1959,36,619. 13. A. I. Vogel, Text Book of Quantitative Inorganic Analysis, p. 433. Longmans, London (1961). 14. M. G. B. Drew, F. S. Esho and S. M. Nelson, J. Chem. Sot., Dalton Trans. 1983, 1653. 15. D. E. Fenton, B. P. Murphy, A. J. Leong, L. F. Lindoy, A. Basheel and M. McPartlin, J. Chem. Sot., Dalton Trans. 1987,2543. 16. J. Bould and B. J. Brisdon, Znorg. Chim. Acta 1976, 19, 159. 17. D. H. Cook and D. E. Fenton, Znorg. Chim. Actu 1977, 25, L95. 18. N. S. Biradar and V. S. Kulkami, J. Znorg. Nucl. Chem. 1971,33,2451.
macrocycles
2325
19. M. C. Jam, A. K. Srivastava and P. C. Jain, Znorg. Chim. Actu 1977,X$ 199. 20. K. G. K. Sundar and K. J. Rao, J. Non Cryst. Solids 1982, SO, 137. 21. B. J. Hathaway and D. E. Billing, Coord. Chem. Rev. 1970,5, 143. 22. I. M. Procter, B. J. Hathaway and P. Nicholls, J. Chem. Sot. A 1968, 1678. 23. B. N. Figgis, Introduction to Ligand Fields, p. 296. Interscience, New York (1966). 24. P. R. Shukla, M. Bhatt and M. C. Sharma, J. Znd. Chem. Sot. 1989,66,192. 25. T. C. Woon and D. P. Fairlie, Znorg. Chem. 1992,31, 4069. 26. J. Reedijk, W. L. Driessen and W. L. Groeneveld, Rec. Trav. Chim. 1969,88, 1095. 27. J. Reedijk, P. W. N. M. Van Leenwen and W. L. Groeneveld, Rec. Trav. Chim. 1968,87, 129. 28. M. J. Bagley, D. Nicholls and B. A. Warburton, J. Chem. Sot. A 1970,2694. 29. D. A. Baldwin, A. B. P. Lever and R. V. Parish, Znorg. Chem. 1969,8, 107. 30. A. B. P. Lever, Inorganic Electronic Spectroscopy. Elsevier, Amsterdam (1968). 31. A. M. Tait and D. H. Busch, Znorg. Chem. 1976,15, 197.