- Email: [email protected]
A study of some transition metal complexes of salicylidene 2-picoloyl hydrazone Schiff base and related ligands
, in.re had ('hem ~ 1 43, pp 5747 Pergamon Press I t d , !081 Printed in Great Britain
A STUDY OF SOME TRANSITION METAL COMPLEXES OF SALICYLIDENE 2-PICOLOYL HYDRAZONE SCHIFF BASE AND RELATED LIGANDS R. L. DUTTA and A. K. SARKAR l)epartment of Chemistry, Inorganic Chemistry Laboratory, The University of Burdwan, Burdwan-713104, India
i tq'rst received 27 February' 1979: received for publication 6 March 1980) Abstract--Salicylidene 2-picoloyl hydrazone, salicylidene 2-quinoloyl hydrazone and salicylidene 8-quinoloyl hydrazone Schiff bases and some related ligands have been synthesised and characterised. Ni(II), Co(Ill, Mn(lI), oxovanadium(IV), oxovanadium(V) and Pd(II) complexes have been prepared and their stereochemistries identified. Flexidentate behaviour of these ligands have also been examined. Under different reaction conditions, the ligands exhibit neutral, monobasic and dibasic tridentate character. Models throw light on the mode of attachment of the ligands to the metal ions.
INTRODUCTION
Synthesis of the complexes (a) Bis(salicylidene 2-picoloyl hydrazone) Co(lI) chloride. Anhydrous ColII) chloride (0.01 moll and the ligand,
Since Sacconi[1] has examined the action of benzoyl hydrazine on diaquo bis(saticylaldehydato) Ni(lI) to obtain bis(salicylidene benzoyl hydrazonato) Ni(II), several chemists have studied hydrazone Schiff bases from the view point of their co-ordinating properties. Recently Iskander et al.[2-4] have published a series of articles dealing with homochelate complexes containing such ligands, while Dutta et al[5] have studied the mixed chelates of oxovanadium(1V) and Cu(II) containing salicylidene benzoyl hydrazone on the one hand and ophenanthroline (or dipyridylt on the other. In this article we report on some selected transition
H2L, (Fig. I)(0.025 moll were separately dissolved in 10 and 25 ml warm methanol respectively. The two solutions were mixed and refluxed for 2 hr. A crystalline yellow compound separated from the refluxing solution. The reaction mixture was cooled to room temperature. The compound was filtered under suction, washed with methanol and dried in air. Similar procedures were adopted for salicylidene 2-quinoloyl--and salicylidene 8quinoloyl ligands; the complexes were also yellow. The ligands obtained from o-hydroxyacetophenone and 2picoloyl-, 2-quinoloyl-or 8-quinoloyl hydrazide were dissolved in appropriate volumes of acetone-alcohol mixture (1 : 1). The solution of the appropriate ligand (0.025 moll was treated with a solution of anhydrous Co(It) chloride (0.01 moll in methanol. The reaction mixture was refluxed for l fir. Gradually a yellow coloured crystalline compound separated. This was filtered, washed with methanol and air dried. A similar reaction with anhydrous Ni(II) chloride and Mn(ll) chloride provided the corresponding bis(ligand) metal(II) halide complexes. (b) Chloro mono (salicylidenato 8-quinoloyl hydrazone) Co(II). The figand, saticylidene 8-quinoloyl hydrazone, H2L", (0.025 moll was dissolved in 50 ml anhydrous methanol and was treated with a solution of anhydrous Co(lI) chloride (0.01 moll in 20 ml methanol. After refluxing for half an hour, a green crystalline product began to separate. After another hour, the mixture was
metal complexes of three such Schiff bases, namely, salicylidene 2-picoloyl hydrazone, salicylidene 2-quinoloyl hydrazone and salicylidene 8-quinoloyl hydrazone (Fig. 1). A survey of the literature[6] reveals only a passing reference to a Sn(IV) complex of salicylidene 2-picoloyl hydrazone. We describe the complexes of these three ligands with Ni(II), Co(lI), Mn(II), oxovanadium(IV and V) and Pd(ll). These studies reveal several modes of attachment of the ligands to the metal ions as well as their ambiprotic character. We have not so far succeeded in getting any Cu(II) chelates of these ligands in a state of reasonable purity. Salicylidene benzoyl hydrazone complexes of Ni(II) and Pd(II) were isolated to help in the characterization of the structures of some of our complexes.
0 EXPERIMENTAl,
Picoloyl hydrazide, 2-quinoloyl hydrazide and 8-quinoloyl hydrazide were prepared by published procedures[7] and the products recrystallized from benzene. The m.p~ of these hydrazides are 100, 135 and 99°C respectively agreeing with the published values[7]. All other materials were Fluka or B.D.H. reagent grade. Preparation of the Schiff bases. All the Schiff bases were prepared by condensing equimolar amounts of the hydrazide and the aldehyde in ethanol on a steam bath. The products were recrystallised from ethanol and then air dried. The Schiff bases are culourless or light yellow in colour. The m.p. and nitrogen analyse', are given in Table I.
OH
0
OH
H2 L
H2 (
(I)
(ll)
N ._/ NH-N=CH- ~ " I O 'O'-t
~2 ~
-c-NH-N=CH-~ r O
OH
H2 ~'
(w)
(rll) Fig. 1. Some substituted salicylidene picoloyl and quinoloyl hydrazone schiff bases. 57
58
R. L. DUTTA and A. K. SARKAR Table 1. Characterisation data of the schiff bases
% of N~
R'- C - NH - N = C - R"
Jl
f
0
R"'
R'
R"
2-1mzridine
o-OHC~4
.
.
2-quinoline ,,
8-qulnoline ,,
Colour
m.p.
(°C)
Cale.
Found
175"
17.4
17.6
R"' H
Light yellow "
CH 3
Grey
185
16.47
16.6
185
14.4
14.6
205
13.7
13.8
"
H
,,
CH 3
"
H
Yellow
147
14.4
14.2
CH 3
Yellow
239-241 (decom)
13.7
13.6
.
* The m.p. 167°C r e p o r t e d
Light yellow
in the literature
~ - 6 _ ~ a p p e a r s t o be
erroneous •
cooled, filtered and the crystals were washed with methanol and dried in air. A similar procedure using Co(II) bromide gave the green coloured bromo-complex. A similar procedure with the ligand derived from the o--hydroxy acetophenone and 8-quinoloyl hydrazide did not produce the expected green coloured mono (ligand) derivative, instead it gave a yellow bis(ligand) Co(II) halide complex, as described in Ca). (c). Bis(salicylidenato 8-quinoloyl hydrazone) Mn(II) and Co(II). Mn(lI) chloride (anhydrous, 0.001 tool) and the ligand, H2L", (0.0025 mol) were separately dissolved in 30 ml and 50 ml of warm methanol respectively. The two solutions were mixed and refluxed on a steam bath. To the resulting hot solution was added a solution of ammonia (1:2) until the solution became just red. The red solution was refluxed further for one hour when a crystalline reddish-brown compound separated. The compound was filtered, washed with rectified spirit and dried in air. The above procedure was modified in the case of Co(It) complex. To a hot solution of Co(II) acetate tetrahydrate (0.01 mol) in 10 ml methanol, a solution of H2L" (0.025 mol) in 50 ml rectified spirit was added and the mixture refluxed for 2 hr. A crystalline deep yellow compound separated from the rettuxing solution. The reaction mixture was cooled to room temperature, filtered, washed with rectified spirit and dried in air. For this synthesis addition of ammonia was not necessary (see preparation of Mn(II) complex). (d). Diaquo mono (salicylidenato 2-picoloyl/2-quinoloyl hydrazonato) oxovanadium(lV) hydrate. Vanadyl sulphate pentahydrate (0.01 mol) and the ligand (0.01 tool) H2L', were separately dissolved in 10 and in 30 ml of warm methanol respectively. The two solutions were mixed, refluxed for 1 hr and then cooled to room temperature. Deep red paramagnetic products were filtered, washed with cold rectified spirit and dried in air. Similar procedure with the 8-quinoloyl ligand gave from the hot reaction mixture a greenish yellow coloured diamagnetic complex.
(e) Dichloro mono (salicylidene 2-picoloyl hydrazone) Pd(II). Pd(II) chloride (0.003 tool) and lithium chloride (0.01 mol were taken in 30 ml of methanol and refluxed on steam bath for 0.5 hr. It was then filtered. To the filtrate 0.006 mol of salicylidene 2-picoloyl hydrazone, H2L, dissolved in 30 ml of methanol, was added and the solution refluxed. After a few minutes, yellow crystalline compound began to separate. After half an hour, the mixture was cooled, filtered and the crystals washed with methanol and dried in air Similar procedures were adopted for the ligands H2L' and H2L" but no crystalline products of definite composition could be isolated. The yellow compound, chloro mono (salicylidenato benzoyl hydrazone) Pd(II) was prepared from Pd(II) chloride and salicylidene benzoyl hydrazone by adopting a method similar to that described above. (f) Bis(salicylidenato benzoyl hydrazone) Ni(lI). The ligand HzL'" (0.025 mol) was dissolved in rectified spirit (30ml) and
refluxed with a rectified spirit (5 ml) solution of anhydrous NiCI2(0.01 mol) for a few minutes. The light yellow compound was filtered, washed with spirit and dried in air. Analysis. The Ni(II) complexes were decomposed to nickel oxide and the nickel determined as the dimethyl glyoximato complex. Cobalt (II) complexes were likewise decomposed to oxide, converted to sulphate and weighed as anhydrous Co(lI) sulphate. Mn(II) complexes were estimated as anhydrous MnSO4. Vanadium complexes were carefully ignited to V205 and weighed. The Pd(II) complexes were ignited to the metal and cooled in a desiccator in an atmosphere of methanol and finally weighed as the metal. The estimations of the halide ions were done by fusing the complexes with AnalaR sodium carbonate and finally precipitating and weighing as silver halides. Nitrogen was estimated by semi-micro Duma's method. Carbon and hydrogen estimations were done at C.D.R.I., Lucknow for some selected samples as a further check. Characterisation data appear in Table 2. Physical measurement. All the IR spectra were carried out at C.D.R.I., Lucknow. Electronic spectra of the complexes were run at R.S.I.C., Madras. Room temperature magnetic susceptibilities were determined with a Gouy balance using CuSO4'5H20 as a calibrant. Diamagnetic corrections were made using Pascal's constants. Solution spectra were run in a Hilger Uvispek spectrophotometer using a cell of suitable path length. Conductance data were obtained using a Philips conductivity bridge in methanol or mitromethane at 0.001 or 0.005 M concentration. RESULTS AND DISCUSSION Salicylidene benzoyl hydrazone (H2L'") is capable of exhibiting either tridentate monobasic or tridentate dibasic ONO behaviour (IV A and IV B). Its neutral tridentate behaviour (IV C) has not been reported nor its behaviour as a b i d e n t a t e - N O - d o n o r .
tl
~
i
Oi - ~
(IVA)
~~ O (IVB)
(ivc) (IVA),(IV B)and
(IVC)
I
R"
R"'
X
"
N~
"
"
Co
Co
2-qu~nollne
N~
8-qu~nollne
"
Cp
N~
"
Ni
"
"
Mn
Co
"
"
"
"
-
-
"
-
"
"
"
CH 3
H
"
UM 3
-
H
-
CH 3
"
"
"
"
"
**
-
"
,,
"
"
"
I. /-M(R'-CO-NH-N--~t-R")2.-7 X 2 . n H 2 0 R- I P-pyrldine o-OHC6H 4 H Cl --
R'
CO
N~
M
Compounds
"
1
-
-
-
"
1
n
green
yellow
green
green
Light yellow
Green
Yellow
Light
Yellow
Yellowish green
Yellow
Greenish yellow
Light
LCght
Light
Colour
7.9 (7.77)
7.9 (8.04)
7.86 (7.96)
7.9 (7.95)
8.3 (~.27)
8.2 (8.24)
9.1 (8.98)
9.6 (8.95)
8.9 (9.03)
i0.0 (9.63)
9.6 (9.6)*
M(~)
14.0 (13.8)
13.E (13.7)
13.2 (13.7)
N(,~)
ii,2 (11.09)
ii,7 (11.52)
11.5 (ii.36)
11.4 (11.36)
12.0 (ll.S)
II.S (II.S)
12.~ (12.8)
12.9 (12.81)
Table 2. Characterisation data of complexes
57.2 (58.39)
57.3 (88.4)
56.8 (57.3)
57.1 (87.3)
C(%)
4.4 (4.05)
4.3 (4.06)
3.68 (3.6~)
4.1 (3.55)
H(~)
CoDtd.
9.6 (9.37)
9.6 (9.13)
i0.0 (9.59)
9.6 (9.6)
lO.O (9.97)
i0.0 (9.97)
ll.1 (I0.S3)
ii.0 (10.93)
Ii.8 (11.68)
11.5 (11.6)
11.57 (ll.6)
X(~)
>
12
=
o
--i
B
o
=
Mn
9-OHC6H 4
H
H
2-qulnollne
v
"
~-0C~4
H
C1
"
1
"
2
Dark red
Dark red
Yellow
Reldish yellow
Yellow
Deep yellow
Green
Green
Colour
(Contd)
14.2 (14.12) 12.3 (12.4)
25.8 (26.4)
8.8 (8.7)
8.2 (8.18)
28.0 (27.93)
(13.7)
13.4
15.0 (16.3)
H(%)
1 Greenish yellow 12.2 (12.4) Calculated values are in parentheses.
6. ~--MO(R'-CO-RH-N--C-R") (OH)2._TH20 R-W ~-qulnollne ~-OC6H 4 H
2-pyrldlne
5. ~-MO(R'-~=N-N--~I-R")(H20)~TH20 o_ R"'
2-pyrldlne
Rnt
R,t o-OC6H 4
4 . L-M (R '-CO-NH-N=C-R") XJ !
8-qulnollne
v
Pd
,,
3. L-MCA'-CO-~-N=C-R") 2_7~2 o
"
CI
C~6
Pd
Cl Br
Co
v
R"'
Co
co
R"
2. ~-M(R'-CO-NH-N=C-R")X_7 ! R- I 8-quinoline o-0C~4 H
R'
Compounds
Table 2.
i0.I (10.2)
12.0 (11.63) 10.3 (10.2)
i0.i (10.04)
12.8 (12.45)
13.0 (12.5)
7.4 (7.36)
9.6 (9.7)
(10.9)
10.8
N(%)
(2.9)
3.3
3.6 (3.1)
~(%)
60.65 4.2 (60.45) (4.15)
61.7 4.4 (60.81) (4.18)
47.6 (47.5)
,53.8 (,53.1)
c(%)
16.8 (16.9)
(9.32)
9.4
18.4 (19.66)
9.2 (9.2)
x(%)
> ~o
>
>
>
A study of some transition metal complexesof salicylidene 2-picoloylhydrazoneschiff base and related ligands
61
~----~-c--N-r~:cH-~ "
S 2~:.(ONO)
2A.(ONO) FO~-C-N H_N=CH_ ~ N-.--_._(_~6) ,/(G) ~H
k~J- C: N- N=CH - ~ N- (C) / (G) - - - O H -_~*~_ 2B' (NNO)
213 (NNO) ~L~-C- NH- N=C H- ~k,~ P ~ (5)',, (7) A , - -~..._,\ ,._.~jf J u H
N___(5)'(7)
(~
2C'.(NNO)
2C. (NNO)
Fig. 2. Possible flexidentate behaviourof salicylidene 2-picoloylhydrazoneschiff base (keto and enol forms).
1. Examination of models Models of salicylidene 2-picoloyl-, salicylidene 2quinoloyl- and salicylidene 8-quinoloyl hydrazone, illustrated in Fig. 2, show that in no case can the ligands exhibit quadridenate-NONO-behaviour. The other possibilities are shown in the figure. When the ligand behaves as a neutral (ONO) donor (Fig. 2A), the pyridine nitrogen does not co-ordinate and the ligand acts just like a schiff base derived from the condensation of benzoylhydrazone and salicylaldehyde (Fig. 1 (IV)]. But when the donor centres are (NNO), the ligand utilises the pyridine nitrogen, one of the hydrazine nitrogens and the phenolic oxygen. In its enol form (Fig. 2), the ligand can function like
the enol form of salicylidene benzoyl hydrazone showing (ONO) linking. The enol forms can, however, behave as (NNO) donors (Figs. 2B' and 2C') where the ring nitrogen, one of the hydrazine nitrogens and the phenolic oxygen are involved. The possible flexidentate character of salicylidene 2-quinoloyl hydrazone ligand will parallel those of the 2-picoloyl analogue. Salicylidene 8-quinoloyl hydrazone offers some more complications. In its keto forms (Figs. 3A-C), with the ring nitrogen co-ordinated to a metal ion, the ligand can not function as an (ONO) donor. In the keto forms (Figs. 3A and B), the ligand may behave as an (NNO) donor where the ring nitrogen, one of the hydrazine nitrogens and the phenolic oxygen are involved in co-ordination
(Keto)
i
~s_ I~1(6)C=O . . . . . . ~ O,..~IH r~l" (7) , '-.~--'- c H =N 3A,(N NO)
(Enol)
N
t
d(G)C- OH ~ i~- ~~-...Nil" rm~"°(7) ~ -CH=N 3,~ (NNO) ~ J
~_ ~!7)~= O
' ,~ N ~(7)C-OH
,
A,O,~ -
=
313.(NNO)
3C.(NOO)
\-~
N
- C H = N
..3B[( N NO )
3C. ( NOO )
Fig. 3. Possible flexidentate behaviours of salicylidene 8quinoloyl hydrazoneschiff base (both in keto and enot form).
62
R. L. DUTTA and A. K. SARKAR
through the formation of seven and six membered ring. If the quinoline nitrogen bonds the metal as also the amide -I (C-O) group via a six membered ring (Fig. 3c), then it is not possible for the hydrazine nitrogen to bond the metal. The phenolic oxygen may, however, be attached to the metal ion via a rather unstable nine membered ring (Fig. 3C). In the enol forms (Figs. 3A' and 3B'), the ligand may function as an (NNO) donor having six membered and seven membered rings. The donor centres are the quinoline nitrogen atom, one of the hydrazine nitrogen and the phenolic oxygen. So far several patterns of behaviour have been noticed. However, if we disregard the possibility of the 8-quinoline nitrogen coming into play as a donor, the ligand then will effectively behave like salicylidene benzoyl hydrazone [Fig. I (IV)].
2. Neutral tridentate ( ONO) behaviour (a) Modes o[ attachment of the three ligands. Salicylidene 2-picoloyl hydrazone (H2L) reacts with NiCI2, COC12 and MnCI2 to give complexes of the type [Ni(H2L)2] C12, [Co(H2L)2] C12 and [Mn(H2L)2] C12. These complexes are bivalent electrolytes [8] in methanol (Table 3) indicating that the two chloride anions are not co-ordinated to the metal ions. The neutral behavior of these ligands compared to the monobasic[3] or dibasic[4, 5], character of salicylidene benzoyl hydrazone is probably a reflection of the overall influence that the basic pyridine nitrogen has on the molecule. The IR spectra (Table 4) of these three complexes are almost superimposable indicating the same sterochemistry. The free ligand (H2L) has a stretching frequency of
Table 3. Magnetic moment and conductibity data of complexes
~
Compounds M
R'
R"
R"'
X
n
| B.M. at r o o m temperature
M o l a r conduetanee o h m s - l e m 2 m o l e -I at 25°C (Solvent)
I. CM(R,-c0-~-~-~-R")~Tx2~2o R"t Ni
2-pyridlne
2-OHc6H 4
H
Cl
-
3.2
1 8 0 (methanol)
Co
"
"
"
"
Mn
"
"
"
"
Ni
"
"
CH 3
"
1
3.1
175 ( m e t h a n o l )
Co
"
"
"
"
"
4.6
167
"
H
C1
-
3.1
193
"
"
"
"
"
-
4.47
168
"
Co
"
"
C~ 3
"
-
4.52
Insoluble
Ni
"
"
"
"
-
3 • 13
"
H
"
1
3.08
180 (methanol)
"
~I 3
"
1
4.8
Insoluble
H
Cl
4.5
49 (methanol)
Br
4.5
20
Ni
2-quinoline
Co
8-qu~noline
N~
Co
"
2. / - M ( R ' - C O - N H - N = C - R " ) X
4.6
158
5 •58
I nsoluble
"
"
"
7
R" t Co
8-~ulnoline
o-0C6H 4
Co
"
"
Pd
C~5
"
3.
"
Cl
Diamagnetic
o-0C~4
H
-
2
5.74
"
"
-
"
4.8
"
5 (nlt romethene)
L-M(a'-co-~-N~-R") ~20 R-f
Mn Co
~-quinollne "
Insoluble "
4 CM(R '-CO-~-~-C-m')X_TX l Pd
~- p y r i d i n e
o-OHC6H 4
H
CI
Diamagnetic
15 (pyridine)
~. CMO(R'-C--N-.-~-R"~(~zO)~20 ~V
2-pyridine
V
2-qulnoline
R" ' R - O C 6H 4 "
e. Z - - ~ ( R ' - C O - ~ - N = ~ - R " )
V
R-quinoline
o-0C~4
H
1
1.62
20 (methanol)
"
1
1.4
18
1
Diamagnetic
Insoluble
"
(O~)~_7~zO
H
-
A study of some transition metal complexes of salicylidene 2-picoloyl hydrozone schiff base and related ligands Table 4. Spectral data of the ligands and their metal complexes Compounds R '
~m-H ~mlde I ~C-N ~M-X ~M--O
R"
R" '
X
R '-CO -NH - N = C - R "
2-pyr~dine
o-OHC6H 4
3520
1670
1620
-
"
CH 3
3333
1690
1600
-
"
H
3300
168:2
1600
-
" 2-qulnollne " 8-qulnoline " Benzene
H
-
"
CH 3
3300
1675
1595
"
H
-
3440
1660
1620
"
CH 3
-
3400
1660
1600
-
"
H
325'0
167f
1600
-
3262
1650
1613
-
L-N~ (R'-c0-~-~ =?-R ,,)e_7x2 2-pyrldlne
o-OHC6H 4
" 2-qulnollne "
8 - q u l n o l l ne
H
Cl
"
CH 3
CI
3390
1613
1590
"
H
CI
3400
1625
1595
"
CH 3
CI
Broad band
"
H
CI
163C
1590
B road band
1610
1600
ECo(R'-C0-~H-~:C-R") J x 2 R" i 2-pyrldlne
o-OHC6H 4
" 2-qulnollne " 8-qulnoline
H
CI
3257
1639
1600
"
CH 3
C1
337B
1613
1600
"
H
C1
3400
1615
1595
"
CH 3
C1
Broad band
1636
1590
-
"
CH 3
C1
3120
1620
1590
-
3247
1626
1600
L-H~(B'-CO-~-~=C-B") i S._7X2 2-pyrldine
o-OHC6H 4
H
CI
CCO(B'-CO-NH-N--C-R")X_7 l R" t R-qulnollne "
o-OC 6B 4 "
H
C1
3400-3500b
1609
1590
290
H
Br
"
1607
1590
260
R" t 9-oul n o l l n e
o-0C6H 4
H
Broad band
1612
1602
1610
1600
Broad band
1600
1560
-
Broad band at :9400
1595
1570
320
/-co (R '-co-,~H-~ =c-R") 2_7H2o R"
R-oulnol~ne
o-OC 6H 4
t
H
-
/-Ni( R'-CO-~,'H =C-R" ) R- I
I
Benzene
o_-OC 6H 4
H
-
Z-m (R' - c o - ~ -N=C-R" )c1_7 Benzene
o-OC 6H 4
H
CI
Contd.
6]
R. L. DUTTA and A. K. SARKAR Table 4. (Contd) Compounds R'
4N-H N"'
~Amide 14C=N
~M-X
4 M=O
X
L-Pd(R'-CO-N~-N:?-R")Clz_7 2-pyrldine
R-OHC~4
H
CI
-
1615
1605
310 365
1625
1610
-
-
1600
-
965
-
1590
-
955
~-VO(R'-CO-NH-N=C-R")(OH)2_TH20 R.t 8-quinol~ne
~-OC6H4
H
3300-3400b
960
L-VO(R'-C=N-N--~I-R")SH20_7 OR"' 2-pyr~dlne
~-OC6H 4
H
2-quiniline
"
H
Broad band "
b
=
broad
the amide-I (C-O) band[9] at 1670cm -~ and of the azomethine (C-N) group[10] at 1620cm -~. In all the three complexes, there is a shift of both the bands to lower frequencies (for C-O band 20--40cm ' and for C-N band 10-20cm -~) indicating that the ligand is attached to the metal ion in its ketoform with the amideI(C-O) group being co-ordinated to the metal ion. Our models show that if (C-O) and (C-N) are attached to the metal ion, then there is no scope for the ring nitrogen to be co-ordinated (see Fig. 2A). The IR spectral data of the complexes,[M(Hy)2] C12 and [M(H2L")2] C12 (where M = Ni(II), Co(II); H2L' and H2L" are salicylidene 2-quinoloyl hydrazone and salicylidene 8-quinoyl hydrazone respectively) show that the ligands are co-ordinated to the metal ions via the amide (C-O) oxygen and azomethine (C-N) nitrogen. Since the position of the ring nitrogen atom in the 2-picoloyl ligand and the 2-quinoloyl ligand are comparable, hence the 2-quinoline nitrogen is again not co-ordinated (see Fig. 2A). If the 8-quinoline nitrogen atom is co-ordinated, then the model predicts a nine membered ring (Fig. 3C) in order to span the phenolic oxygen. This is rather improbable and there is also a clear indication of attachment of the azomethine group (lowering of C-N band 15 cm-'). (b) Magnetic moment, conductivity and electronic
spectra of bis(salicylidene 2-picoloyll2-quinoloyl/8quinoloyl hydrazone) Ni(II) halide complexes. The Ni(II) complexes are green to yellowish green (Table 2) and are paramagnetic (/~ = 3.1-3.2 BM, Table 3) which suggests octahedral geometry. [l l]. The electronic spectra of most of the complexes are ill resolved (Table 5). Of the several complexes for which mull spectra have been obtained, one, namely, bis (salicylidene 8-quinoloyl hydrazone) Ni(II) chloride gives the three expected absorption bands at 11.2, 17.3 and 28.5 kK[12]. These three bands may be assigned to 3A2g~3T2g(/),);3A2~ 3 T,g(/)2); and 3A2g --)3 I"1~(P)(u3) respectively. The v2[v,, ratio ~1.54 is in conformity with octahedral geometry[13, 14]. It is of interest to note that an attempted synthesis of [Ni(H2L'")2]CI2 (where H2L' ' = salicylidene benzoyl hydrazor.e) via an interaction of anhy-
drous NiC12 and H2L'" led not to the desired product but to [Ni(HL'")2]. This complex was originally synthesised by Sacconi[l] using [Ni(salh] (salH=salicylaldehyde) and benzoyl hydrazide. Formation of [Ni(HL'")2] is a manifestation of the preponderance of the monobasic tridentate behaviour of H2L'". (c) Electronic spectra and magnetic moment o[ bis(salicylidene 2-picoloyl/2-quinoloyl hydrazone) Co(II) halide complexes. The Co(II) complexes have magnetic moments (/x=4.5-4.6BM), on the lower side of the octahedral Co(II) range[15]. The electronic spectra (Table 5) of the Co(lI) complexes are rather well resolved and show bands at 8-8.7 kK, 16-16.3 kK and near 17-18.2kK. In octahedral symmetry[16], these bands may be assigned to the transitions 4T,~ ~4T2~(v0; 4T,e ~4A2~(/)2; and 4T,~ ~4T,(P)(v3) respectively. The ratios of v2//),, are in the range (1.82-2.2) as is expected for Co(II) octahedral stereochemistry[16, 17]. Assuming the first absorption band in our complexes as v~ = 8 Dq, the calculated v2 (=18 Dq) is consistent with the second band observed in these complexes. The molar conductance (AM) values for the Co(II) complexes (Table 3) indicate their bi-univalent electrolytic character. (d) Bis(salicylidene 2-picoloyl hydrazone) Mn(II) chloride. Only one such complex namely [Mn(H2L)2] 02 has been obtained in crystalline form. Attempts to obtain corresponding complexes with H2L' and H2L" produced only slimy products which are difficult to filter. The experimental moment (# = 5.58 BM) is, however below the spin only moment. A conductance measurement was not possible due to poor solubility in suitable solvents.
3. Monobasic tridentate ( ONO) behaviour Such behaviour has been observed with salicylidene 8-quinolyl hydrazone ligand but not as yet with salicylidene 2-picoloyl/2-quinoloyl hydrazone ligands. (a). Chloromono (salicylidenato 8-quinoloyl hydrazone) Co(II). Co(II) chloride and Co(II) bromide react with salicylidene 8-quinoloyl hydrazone to give light green complexes of the type [Co(HL")X]n (where X = CI, Br and H2L" = salicylidene 8-quinoloyl hydrazone). The IR spectra of the ligand show characteristic sharp ab-
A study of some transition metal complexes of salicylidene 2-picoloyl hydrazone schiff base and related ligands
could be suggested. The magnetic moment (# 4.5 BM) rules out a square planar structure. The stretching frequency of ~,(Co-Cl) and t,(Co--Br) for these corn.. plexes are =29(I and 260 cm-' respectively (Table 4). It is pertinent to mention that the stretching frequency[18] of v(Co-CI) and t,(Co--Br) of monomeric octahedral Co(II) complexes are around 230cm -~ and =200cm ' respectively and for tetrahedral Co(II) complexes t,(Co(Cl) and v(Co--Br) are =320 cm-Z and =270 cm ' respectively. A light green colour is less likely for a tetrahedral structure. The electronic spectra (in Nujol mull) resemble (Table 5) a six-co-ordinate polymeric octahedral structure rather than a tetrahedral or a five co-ordinate one (Section VI). (b) Bis (salicylidenato 8-quinoloyl hydrazone) Mn(II) and Co(II). Mn(lI) chloride reacts with the 8-quinoloyl Iigand to give a light red coloured [Mn(HL")j complex (where H2L" = salicylidene 8-quinoloyl hydrazone). Due to poor solubility in common organic solvents, conductance measurement and molecular weight determinations were not possible. Comparison of the IR spectra of the ligand and complex shows a lowering in the frequency of both the bands
sorption bands at 3440, 1660 and 1620cm-' (Table 4). These bands are assigned to u(N-H), ~,(C-O) and v(C-N) stretches respectively. In the light green Co(II) complexes, there is a distinct shift of C-O and C-N bands to lower frequencies (for C-O, A~,=45cm-' and C-N, A~,~-10cm '), indicating that the ligand is attached to the metal ion in its keto form and co-ordination takes place through (C-N) nitrogen and (C-O) oxygen atom. It is obvious that electroneutrality is achieved through the deprotonation of the phenolic -OH group. The models showed that if the (C-O) and (C-N) groups are attached, to the metal ion then there is no possibility for the ring nitrogen to be co-ordinated. These complexes are soluble only in donor solvents such as pyridine, dimethylsulfoxide etc. The conductivity in methanol at 10-4M gives a value -15-20ohm 'cm2mol J (Table 3). The magnetic moments (Table 3) of the complexes are on the border line of tetrahedral and octahedral complexes. In fact several structures, namely, a four co-ordinate square planar, a tetrahedral, a five co-ordinate dimeric structure with bridging oxygen and terminal X, and also a polymeric halogen-bridged and oxygen-bridged structures
=
Table 5. Electronic spectral data for Co(lI) and Ni(lI) chelates Chelates
State R'
R"
R"'
X
Absorption bands i n k K
n
d-N~ (R'-CO-~-N=C-R")2_TX2.nH20 o-OHC6H 4
H
CI
2-quinollne
"
"
"
,,
28.5
,,
CH3
"
,,
27.7
"
H
"
"
28..5
R-qulnollne
-
Reflectance
2-Pyrldlne
,,
1
26.6 ~ ) 7 16.9
ii. Benzene
o-OC6H 4
H
-
"
2
:L'
"~
28.26 ~ 3 17.4
~2
io.8 ~i
Z-c o( R '-CO-~-N~-R")_Tx 2.nil20 R" ! ~-pyridlne
o-OHC6H a
H
CI
"
H
"
-
Reflectance
_% 18.1 16.0
,~'3 "*)2
8.3 ~,
9-qu:l n o l l n e
18.0 (sh) 16.0 (sh) 16.0
CH 3
(sh)
18.1 (sh) ~-aul nollne
"
H
"
I
H
CI
-
"
23.Z 16.13
H
Br
-
"
23.5 16.2 8.5
2
Reflectance
18.02 16.00
16.0 8.7
~-Co (R '-CO-N~I-N:C-R") X 7 R" t ~-~ i n o l l n e
"
o-OC6H 4
"
/ - C r ( R '-CO -NH - N = C - R " ) 232I[20 I
q-oulnollne
JINC
"~oJ~ No I--E
o-OC6R 4
H
-
65
(sh) (sh)
66
R. L. DUTTA and A. K. SARKAR
(C-O) and C-N for the complex (for C-O band, Av = 30cm -~ and for C-N, Av-~7cm -~ (Table 4). It is concluded that the ligand reacts with Mn(II) in its keto form and co-ordination takes place via (C-O) oxygen and (CN) nitrogen atom. Electroneutrality is achieved through deprotonation of the phenolic OH group. The magnetic moment (# = 5.7 BM) and electronic spectra of Mn(II) are not indicative of its stereochemistry. However, since the ligand suffers deprotonation of its phenolic -OH group, we suggest that the complex is pseudo-octahedral and that the ligand functions as tridentate monobasic (ONO) form. We have not so far succeeded in isolating products like [NI(HL)2], [Ni(HL')2] and [Ni(HL")2] while [Ni(HL'")2] is well characterised. This inner metallic complex exhibits bands at 10.8, 17.4 and 23.26 kK. It appears that the ligand H2L"' is weaker (~ = 10Dq= 10.8kK) than the neutral H2L" (v~ = 10 Dq = 11.2 kK) (see Table 5). The IR spectral data of the deep yellow complex, bis(salicylidenato 8-quinoloyl hydrazone) Co(II), shows that the ligand is attached to the Co(II) via (C-N) nitrogen, (C-O) oxygen and phenolic oxygen atom (Table 4). The deprotonation takes place from the phenolic hydrogen. A pseudo-octahedral structure is suggested from the magnetic measurement[15] and electronic spectrum (Table 5). Due to poor solubility in common organic solvents, a conductance determination was not possible. (c) Oxo-dihydroxo mono (salicylidenato 8-quinoloyl hydrazone) vanadium(V) monohydrate. The 8-quinoloyl ligand (H2L") reacts with oxovanadium (iv) sulphate in a way which is distinctly different from the reaction of the other two ligands. While the 2-picoloyl and the 2quinoloyl ligands provide dark red, paramagnetic samples, the 8-quinoloyl ligand gives a greenish brown diamagnetic material, [VO(HL")(OH)2]-H20. Its IR spectrum shows that the amide-I(C-O) band is retained although lowered in frequency by =25 cm -~ (Table 4). It also reveals a strong and very broad hydroxyl band around 3350-3450cm -~. The co-ordination of the azomethine group is also indicated by a small shift Av = 10 cm ~ of the C-N stretch compared to that in the free ligand. Thermal analysis shows a loss of 5% (required 4.4% for one H20). The complex then proceeds to decompose further in a slow step up to 220°C (total loss at this stage being 9.9%). It rapidly decomposes to give V205 at 1000°C (total loss--80%; required---77.8%). Possibly the V(IV) is oxidized in the complex.
cules of water. In the oven at ll0°C, [VO(L)(H20)2] H20, loses one H20, while a thermogravimetric study reveals two slightly overlapping water losses--the first a loss of 6.2% over the temperature range 500110°C and the second a loss of 7.5% over the range 110-280°C. The total loss is 13.7%, while the calculated loss for three molecules of water is 15%. The complexes are paramagnetic (Table 3). Unfortunately only one absorption band around 20-23 kK is identifiable.
5. Neutral bidentate (ON) behaviour of salicylidene 2-picoloyl hydrazone The behaviour of salicylidene benzoyl hydrazone (H2L'") and salicylidene 2-picoloyl hydrazone (H2L) towards Pd(II) is quite different. The former ligand suffers partial deprotonation to give [Pd(HL'")CI]. The IR spectral data for this complex shows that there is a distinct shift of both the C-O and C-N bands to lower frequency (Table 4) from the positions for the free ligand. The molar conductance in nitromethane (5ohm ~cm2mole-') indicate that the compound is nonelectrolytic. The Pd-CI stretch in the far-IR region is found at 320cm-'[20]. A monomeric square planar complex with H2L'" behaving as a monobasic tridentate ligand is thus suggested. Salicylidene 2-picoloyl hydrazone (H2L), being less acidic, reacts with chloropalladite ion to produce [Pd(H2L)CI2]. The IR spectral data (Table 4) indicate that there is a shift of both the C-O and C-N bands (for C-O, A~,=55cm-~; and for C-N, Av=15cm -t) to lower frequencies, indicating attachment through C-O and CN. Two sharp bands at 310 and 365 cm -z are found in the far-IR region. These bands are assigned to Pd-CI stretches[21,22]. The molar conductance value in pyridine (AM=15fl-~cm2mol) shows some slight dissociation in pyridine. A five co-ordinate, nonelectrolytic, monomeric structure is not very likely because the few such complexes known for palladium (II) are with ligands having soft donors like As, P,[23]. The obvious conclusion is that the ligand H2L functions as a bidentate NO donor.
6. Exceptional behaviour of salicylidene 8-quinoloyl hydrazone ligand
The 2-picoloyl and the 2-quinoloyl ligands behave alike while the 8-quinoloyl ligand shows exceptional behaviour. for instance in its Co(II) complexes [Co(HL")X],(X = CI, Br). The Co(II) complexes of the other two ligands conform to the composition [Co(H2Lh]X2 and 4. Dibasic tridentate (ONO) behaviour. Oxovanadium [Co(H2L'h]X2. In none of these complexes, is there any (IV) complexes o[ salicylidene 2-picoloyl/2-quinoloyl evidence in favour of participation of the heterocyclic hydrazone nitrogen. A comparison of the acid/base character For the oxovanadium (IV) complexes of 2-picoloyl and 2-quinoloyl ligands, (VO(L)(H20)2] H20 and [VO(L') (H20)2] H20, (H2L = salicylidene 2-picoloyl hydrazone; H2L'= salicylidene 2-quinoloyl hydrazone), the IR spectra reveal a strong (V-O) stretch[19] around 955%5cm-L There is no amide-I(C-O) band found at 1670cm -~ for the 2-picoloyl ligand and at 1675 cm -~ for o the 2-quinoloyl ligand. There is also the expected lowering of the C-N band (Av = 13cm ~ for the 2-picoloyl ligand and Av = 10 crn -2 for the 2-quinoloyl ligand). We o i o conclude that co-ordination takes place through the (Cx × N) nitrogen and that the ligands interact with the oxovanadium (IV) in the enol form and lose, in the process, both the enolic hydrogen and the phenolic hydrogen. Elemental analysis (V, N, H20) fit with three moleFig. 4.
,,\ study of some transition metal complexes of salicylidene 2-picoloyl hydrazone schiff base and related ligands [24, 25] of the heterocylic carboxylic acids (2picolinic acid, Pka = 5.1; 2-quinaldinic acid, PkA = 4.% and quinoline 8-carboxylic acid PkA = 7.2; see benzoic acid, PkA = 4.17) shows that quinoline 8-carboxylic acid is the weakest while the benzoic acid is the strongest acid among the four. It is, therefore, not surprising that while salicylidene benzoyl hydrazone has so far not shown any neutral tridentate (ONO) behaviour, all the three ligands under investigations, show neutral (ONO) behaviour under certain conditions. For the green [Co/HL"iX] n(X = CI, Bri, it is proposed that the introduction of one HL" around the Co(II) absorbs much of the electron-accepting power of the metal, compared to, say Ni(lIt, so that it is not possible to introduce a second molecule. Instead, to satisfy octahedral geometry, the metal ion responds through polymerisation via bridging bah)gen and bridging (ON()) groups (Fig. 4). It is fascinating to note that the ligand derived from the interaction of the 8-quinoloyl hydrazide and ohydroxyacetophenone does not give the polymeric light green Co(II) complexes. Instead, we get bis(ligand) Co(II) halides. It is obvious that the inductive effect of lhe ~CH, group makes the phenolic (-OH)less acidic, thus preventing deprotonation. That this 8-quinoloyl ligand is unique among the three heterocyclic substituted ligands (H~I,, H~L' and HzL") so for studied is also indicated by its reaction towards oxovanadium (IV) t,~ produce ~ diamagnetic possibly quinquevalent oxo~anadium (V) complex. This behaviour may also be credited to its comparatively weaker acid, i.e. stronger b~sic character.
REFFRENCES
'. L. Sacconi. J. 4m. Chem. Soc. 74, 4503 (1952). 2 I El Sayed and M. F lsakander, J. lnorg. Nucl. Chem. 33, 435 (1971).
67
3. M. F. Isakander and L. El. Sayed, lnorg. ('him. Acta 16, 147 (1976). 4. M. F. lskander and A. M, El. Aggan, lnorg. Chim. Acta 14, 167, (1975). 5. R. L. Dutta and S. P. Banerjee, J. Indian Chem. Soe. 5l, 497, (1974~. 6. C. Pelizzi and G. Pelizzi, lnor~. ('him. Acta 18, 139, {1976). 7, A. H. Cook, I M. Heilbron and L. Steger, J. Chem. Soe. 413 (1943). 8. W. J. Geary, Co-ord. Chem. Rev. 7, 1-81 H971), 9. M. Mashima, Bull. Chem. Soc. Japan 35. 1882 11%2): ~, 210 (1%3). I0. L. J. Bellamy, The IR Spectra of Complex Molecule~, 3rd Edn. Methuen, London (1%6). l l. R. B. Heslop and P. L. Robinson, Inorganic ('hemi~try, p. 702. Elsevier, New York, (1%7). 12. A, B. P. Lever, Inorganic Eleetnmic Spectroscopy, p. 333. Elsevier, Amslerdam 11%8). 13. D. W. Meek. R. S. Drago and T. S. Piper, lno(¢ ('hem. I. 285 ~1962). 14. L. Sacconi, Transition Metal Chemisto' (Edited by R. L. Carlin, Vol. 4, p. 212. Marcel Decker, New York (1%81. 15. E. K. Barefiehl, D. H. Busch and S. M. Nelson, Quart. Rev. 22, 457 {1%8). 16. R. L. Carlin, Transition Metal Chemistry (Edited by R. L. Carlin, Vol. 1, p. 320. Marcel Decker, New York, {1%5). 17. A. D. Liehr, J. Phys. Chem. 67, 1314 (1%3). 18. D. A. Baldwin, A. B. P. Lever and R. V. Parish, lnom. ('hem. 8, 107, (1%9t. 19. M. Plytzanopoulos, G. Pneumatikakis, N. Hadjuliadis and D. Katakis, J. lnor~'. Nucl, Chem. 39, %5 (1977). 20. Robin J. H. C~ark and C. S. Williams, lno(~,. Chem. 4, 3~(t (1965). 21. L. Caglioti, L. Cattalini, M. Ghedini, F. Gasparrini and P. A. Vigato, J. Chem. Soc. Dalton 514 (1972). 22. R. A. Walton, ~pectmchim. Acta 21, 1795, (1%5). 23. C. Furlani, Coord. Chem. Rev. 3, 141-167 (1%8). 24. W. R. Maxwell and J. R. Partington, Trans. Faraday Soc. 33, 670, (1937). 25. R. C. Elderfield and M. Siegel, J. Am. Chem. Soe. 73, 5622, (1951).
A STUDY OF SOME TRANSITION METAL COMPLEXES OF SALICYLIDENE 2-PICOLOYL HYDRAZONE SCHIFF BASE AND RELATED LIGANDS R. L. DUTTA and A. K. SARKAR l)epartment of Chemistry, Inorganic Chemistry Laboratory, The University of Burdwan, Burdwan-713104, India
i tq'rst received 27 February' 1979: received for publication 6 March 1980) Abstract--Salicylidene 2-picoloyl hydrazone, salicylidene 2-quinoloyl hydrazone and salicylidene 8-quinoloyl hydrazone Schiff bases and some related ligands have been synthesised and characterised. Ni(II), Co(Ill, Mn(lI), oxovanadium(IV), oxovanadium(V) and Pd(II) complexes have been prepared and their stereochemistries identified. Flexidentate behaviour of these ligands have also been examined. Under different reaction conditions, the ligands exhibit neutral, monobasic and dibasic tridentate character. Models throw light on the mode of attachment of the ligands to the metal ions.
INTRODUCTION
Synthesis of the complexes (a) Bis(salicylidene 2-picoloyl hydrazone) Co(lI) chloride. Anhydrous ColII) chloride (0.01 moll and the ligand,
Since Sacconi[1] has examined the action of benzoyl hydrazine on diaquo bis(saticylaldehydato) Ni(lI) to obtain bis(salicylidene benzoyl hydrazonato) Ni(II), several chemists have studied hydrazone Schiff bases from the view point of their co-ordinating properties. Recently Iskander et al.[2-4] have published a series of articles dealing with homochelate complexes containing such ligands, while Dutta et al[5] have studied the mixed chelates of oxovanadium(1V) and Cu(II) containing salicylidene benzoyl hydrazone on the one hand and ophenanthroline (or dipyridylt on the other. In this article we report on some selected transition
H2L, (Fig. I)(0.025 moll were separately dissolved in 10 and 25 ml warm methanol respectively. The two solutions were mixed and refluxed for 2 hr. A crystalline yellow compound separated from the refluxing solution. The reaction mixture was cooled to room temperature. The compound was filtered under suction, washed with methanol and dried in air. Similar procedures were adopted for salicylidene 2-quinoloyl--and salicylidene 8quinoloyl ligands; the complexes were also yellow. The ligands obtained from o-hydroxyacetophenone and 2picoloyl-, 2-quinoloyl-or 8-quinoloyl hydrazide were dissolved in appropriate volumes of acetone-alcohol mixture (1 : 1). The solution of the appropriate ligand (0.025 moll was treated with a solution of anhydrous Co(It) chloride (0.01 moll in methanol. The reaction mixture was refluxed for l fir. Gradually a yellow coloured crystalline compound separated. This was filtered, washed with methanol and air dried. A similar reaction with anhydrous Ni(II) chloride and Mn(ll) chloride provided the corresponding bis(ligand) metal(II) halide complexes. (b) Chloro mono (salicylidenato 8-quinoloyl hydrazone) Co(II). The figand, saticylidene 8-quinoloyl hydrazone, H2L", (0.025 moll was dissolved in 50 ml anhydrous methanol and was treated with a solution of anhydrous Co(lI) chloride (0.01 moll in 20 ml methanol. After refluxing for half an hour, a green crystalline product began to separate. After another hour, the mixture was
metal complexes of three such Schiff bases, namely, salicylidene 2-picoloyl hydrazone, salicylidene 2-quinoloyl hydrazone and salicylidene 8-quinoloyl hydrazone (Fig. 1). A survey of the literature[6] reveals only a passing reference to a Sn(IV) complex of salicylidene 2-picoloyl hydrazone. We describe the complexes of these three ligands with Ni(II), Co(lI), Mn(II), oxovanadium(IV and V) and Pd(ll). These studies reveal several modes of attachment of the ligands to the metal ions as well as their ambiprotic character. We have not so far succeeded in getting any Cu(II) chelates of these ligands in a state of reasonable purity. Salicylidene benzoyl hydrazone complexes of Ni(II) and Pd(II) were isolated to help in the characterization of the structures of some of our complexes.
0 EXPERIMENTAl,
Picoloyl hydrazide, 2-quinoloyl hydrazide and 8-quinoloyl hydrazide were prepared by published procedures[7] and the products recrystallized from benzene. The m.p~ of these hydrazides are 100, 135 and 99°C respectively agreeing with the published values[7]. All other materials were Fluka or B.D.H. reagent grade. Preparation of the Schiff bases. All the Schiff bases were prepared by condensing equimolar amounts of the hydrazide and the aldehyde in ethanol on a steam bath. The products were recrystallised from ethanol and then air dried. The Schiff bases are culourless or light yellow in colour. The m.p. and nitrogen analyse', are given in Table I.
OH
0
OH
H2 L
H2 (
(I)
(ll)
N ._/ NH-N=CH- ~ " I O 'O'-t
~2 ~
-c-NH-N=CH-~ r O
OH
H2 ~'
(w)
(rll) Fig. 1. Some substituted salicylidene picoloyl and quinoloyl hydrazone schiff bases. 57
58
R. L. DUTTA and A. K. SARKAR Table 1. Characterisation data of the schiff bases
% of N~
R'- C - NH - N = C - R"
Jl
f
0
R"'
R'
R"
2-1mzridine
o-OHC~4
.
.
2-quinoline ,,
8-qulnoline ,,
Colour
m.p.
(°C)
Cale.
Found
175"
17.4
17.6
R"' H
Light yellow "
CH 3
Grey
185
16.47
16.6
185
14.4
14.6
205
13.7
13.8
"
H
,,
CH 3
"
H
Yellow
147
14.4
14.2
CH 3
Yellow
239-241 (decom)
13.7
13.6
.
* The m.p. 167°C r e p o r t e d
Light yellow
in the literature
~ - 6 _ ~ a p p e a r s t o be
erroneous •
cooled, filtered and the crystals were washed with methanol and dried in air. A similar procedure using Co(II) bromide gave the green coloured bromo-complex. A similar procedure with the ligand derived from the o--hydroxy acetophenone and 8-quinoloyl hydrazide did not produce the expected green coloured mono (ligand) derivative, instead it gave a yellow bis(ligand) Co(II) halide complex, as described in Ca). (c). Bis(salicylidenato 8-quinoloyl hydrazone) Mn(II) and Co(II). Mn(lI) chloride (anhydrous, 0.001 tool) and the ligand, H2L", (0.0025 mol) were separately dissolved in 30 ml and 50 ml of warm methanol respectively. The two solutions were mixed and refluxed on a steam bath. To the resulting hot solution was added a solution of ammonia (1:2) until the solution became just red. The red solution was refluxed further for one hour when a crystalline reddish-brown compound separated. The compound was filtered, washed with rectified spirit and dried in air. The above procedure was modified in the case of Co(It) complex. To a hot solution of Co(II) acetate tetrahydrate (0.01 mol) in 10 ml methanol, a solution of H2L" (0.025 mol) in 50 ml rectified spirit was added and the mixture refluxed for 2 hr. A crystalline deep yellow compound separated from the rettuxing solution. The reaction mixture was cooled to room temperature, filtered, washed with rectified spirit and dried in air. For this synthesis addition of ammonia was not necessary (see preparation of Mn(II) complex). (d). Diaquo mono (salicylidenato 2-picoloyl/2-quinoloyl hydrazonato) oxovanadium(lV) hydrate. Vanadyl sulphate pentahydrate (0.01 mol) and the ligand (0.01 tool) H2L', were separately dissolved in 10 and in 30 ml of warm methanol respectively. The two solutions were mixed, refluxed for 1 hr and then cooled to room temperature. Deep red paramagnetic products were filtered, washed with cold rectified spirit and dried in air. Similar procedure with the 8-quinoloyl ligand gave from the hot reaction mixture a greenish yellow coloured diamagnetic complex.
(e) Dichloro mono (salicylidene 2-picoloyl hydrazone) Pd(II). Pd(II) chloride (0.003 tool) and lithium chloride (0.01 mol were taken in 30 ml of methanol and refluxed on steam bath for 0.5 hr. It was then filtered. To the filtrate 0.006 mol of salicylidene 2-picoloyl hydrazone, H2L, dissolved in 30 ml of methanol, was added and the solution refluxed. After a few minutes, yellow crystalline compound began to separate. After half an hour, the mixture was cooled, filtered and the crystals washed with methanol and dried in air Similar procedures were adopted for the ligands H2L' and H2L" but no crystalline products of definite composition could be isolated. The yellow compound, chloro mono (salicylidenato benzoyl hydrazone) Pd(II) was prepared from Pd(II) chloride and salicylidene benzoyl hydrazone by adopting a method similar to that described above. (f) Bis(salicylidenato benzoyl hydrazone) Ni(lI). The ligand HzL'" (0.025 mol) was dissolved in rectified spirit (30ml) and
refluxed with a rectified spirit (5 ml) solution of anhydrous NiCI2(0.01 mol) for a few minutes. The light yellow compound was filtered, washed with spirit and dried in air. Analysis. The Ni(II) complexes were decomposed to nickel oxide and the nickel determined as the dimethyl glyoximato complex. Cobalt (II) complexes were likewise decomposed to oxide, converted to sulphate and weighed as anhydrous Co(lI) sulphate. Mn(II) complexes were estimated as anhydrous MnSO4. Vanadium complexes were carefully ignited to V205 and weighed. The Pd(II) complexes were ignited to the metal and cooled in a desiccator in an atmosphere of methanol and finally weighed as the metal. The estimations of the halide ions were done by fusing the complexes with AnalaR sodium carbonate and finally precipitating and weighing as silver halides. Nitrogen was estimated by semi-micro Duma's method. Carbon and hydrogen estimations were done at C.D.R.I., Lucknow for some selected samples as a further check. Characterisation data appear in Table 2. Physical measurement. All the IR spectra were carried out at C.D.R.I., Lucknow. Electronic spectra of the complexes were run at R.S.I.C., Madras. Room temperature magnetic susceptibilities were determined with a Gouy balance using CuSO4'5H20 as a calibrant. Diamagnetic corrections were made using Pascal's constants. Solution spectra were run in a Hilger Uvispek spectrophotometer using a cell of suitable path length. Conductance data were obtained using a Philips conductivity bridge in methanol or mitromethane at 0.001 or 0.005 M concentration. RESULTS AND DISCUSSION Salicylidene benzoyl hydrazone (H2L'") is capable of exhibiting either tridentate monobasic or tridentate dibasic ONO behaviour (IV A and IV B). Its neutral tridentate behaviour (IV C) has not been reported nor its behaviour as a b i d e n t a t e - N O - d o n o r .
tl
~
i
Oi - ~
(IVA)
~~ O (IVB)
(ivc) (IVA),(IV B)and
(IVC)
I
R"
R"'
X
"
N~
"
"
Co
Co
2-qu~nollne
N~
8-qu~nollne
"
Cp
N~
"
Ni
"
"
Mn
Co
"
"
"
"
-
-
"
-
"
"
"
CH 3
H
"
UM 3
-
H
-
CH 3
"
"
"
"
"
**
-
"
,,
"
"
"
I. /-M(R'-CO-NH-N--~t-R")2.-7 X 2 . n H 2 0 R- I P-pyrldine o-OHC6H 4 H Cl --
R'
CO
N~
M
Compounds
"
1
-
-
-
"
1
n
green
yellow
green
green
Light yellow
Green
Yellow
Light
Yellow
Yellowish green
Yellow
Greenish yellow
Light
LCght
Light
Colour
7.9 (7.77)
7.9 (8.04)
7.86 (7.96)
7.9 (7.95)
8.3 (~.27)
8.2 (8.24)
9.1 (8.98)
9.6 (8.95)
8.9 (9.03)
i0.0 (9.63)
9.6 (9.6)*
M(~)
14.0 (13.8)
13.E (13.7)
13.2 (13.7)
N(,~)
ii,2 (11.09)
ii,7 (11.52)
11.5 (ii.36)
11.4 (11.36)
12.0 (ll.S)
II.S (II.S)
12.~ (12.8)
12.9 (12.81)
Table 2. Characterisation data of complexes
57.2 (58.39)
57.3 (88.4)
56.8 (57.3)
57.1 (87.3)
C(%)
4.4 (4.05)
4.3 (4.06)
3.68 (3.6~)
4.1 (3.55)
H(~)
CoDtd.
9.6 (9.37)
9.6 (9.13)
i0.0 (9.59)
9.6 (9.6)
lO.O (9.97)
i0.0 (9.97)
ll.1 (I0.S3)
ii.0 (10.93)
Ii.8 (11.68)
11.5 (11.6)
11.57 (ll.6)
X(~)
>
12
=
o
--i
B
o
=
Mn
9-OHC6H 4
H
H
2-qulnollne
v
"
~-0C~4
H
C1
"
1
"
2
Dark red
Dark red
Yellow
Reldish yellow
Yellow
Deep yellow
Green
Green
Colour
(Contd)
14.2 (14.12) 12.3 (12.4)
25.8 (26.4)
8.8 (8.7)
8.2 (8.18)
28.0 (27.93)
(13.7)
13.4
15.0 (16.3)
H(%)
1 Greenish yellow 12.2 (12.4) Calculated values are in parentheses.
6. ~--MO(R'-CO-RH-N--C-R") (OH)2._TH20 R-W ~-qulnollne ~-OC6H 4 H
2-pyrldlne
5. ~-MO(R'-~=N-N--~I-R")(H20)~TH20 o_ R"'
2-pyrldlne
Rnt
R,t o-OC6H 4
4 . L-M (R '-CO-NH-N=C-R") XJ !
8-qulnollne
v
Pd
,,
3. L-MCA'-CO-~-N=C-R") 2_7~2 o
"
CI
C~6
Pd
Cl Br
Co
v
R"'
Co
co
R"
2. ~-M(R'-CO-NH-N=C-R")X_7 ! R- I 8-quinoline o-0C~4 H
R'
Compounds
Table 2.
i0.I (10.2)
12.0 (11.63) 10.3 (10.2)
i0.i (10.04)
12.8 (12.45)
13.0 (12.5)
7.4 (7.36)
9.6 (9.7)
(10.9)
10.8
N(%)
(2.9)
3.3
3.6 (3.1)
~(%)
60.65 4.2 (60.45) (4.15)
61.7 4.4 (60.81) (4.18)
47.6 (47.5)
,53.8 (,53.1)
c(%)
16.8 (16.9)
(9.32)
9.4
18.4 (19.66)
9.2 (9.2)
x(%)
> ~o
>
>
>
A study of some transition metal complexesof salicylidene 2-picoloylhydrazoneschiff base and related ligands
61
~----~-c--N-r~:cH-~ "
S 2~:.(ONO)
2A.(ONO) FO~-C-N H_N=CH_ ~ N-.--_._(_~6) ,/(G) ~H
k~J- C: N- N=CH - ~ N- (C) / (G) - - - O H -_~*~_ 2B' (NNO)
213 (NNO) ~L~-C- NH- N=C H- ~k,~ P ~ (5)',, (7) A , - -~..._,\ ,._.~jf J u H
N___(5)'(7)
(~
2C'.(NNO)
2C. (NNO)
Fig. 2. Possible flexidentate behaviourof salicylidene 2-picoloylhydrazoneschiff base (keto and enol forms).
1. Examination of models Models of salicylidene 2-picoloyl-, salicylidene 2quinoloyl- and salicylidene 8-quinoloyl hydrazone, illustrated in Fig. 2, show that in no case can the ligands exhibit quadridenate-NONO-behaviour. The other possibilities are shown in the figure. When the ligand behaves as a neutral (ONO) donor (Fig. 2A), the pyridine nitrogen does not co-ordinate and the ligand acts just like a schiff base derived from the condensation of benzoylhydrazone and salicylaldehyde (Fig. 1 (IV)]. But when the donor centres are (NNO), the ligand utilises the pyridine nitrogen, one of the hydrazine nitrogens and the phenolic oxygen. In its enol form (Fig. 2), the ligand can function like
the enol form of salicylidene benzoyl hydrazone showing (ONO) linking. The enol forms can, however, behave as (NNO) donors (Figs. 2B' and 2C') where the ring nitrogen, one of the hydrazine nitrogens and the phenolic oxygen are involved. The possible flexidentate character of salicylidene 2-quinoloyl hydrazone ligand will parallel those of the 2-picoloyl analogue. Salicylidene 8-quinoloyl hydrazone offers some more complications. In its keto forms (Figs. 3A-C), with the ring nitrogen co-ordinated to a metal ion, the ligand can not function as an (ONO) donor. In the keto forms (Figs. 3A and B), the ligand may behave as an (NNO) donor where the ring nitrogen, one of the hydrazine nitrogens and the phenolic oxygen are involved in co-ordination
(Keto)
i
~s_ I~1(6)C=O . . . . . . ~ O,..~IH r~l" (7) , '-.~--'- c H =N 3A,(N NO)
(Enol)
N
t
d(G)C- OH ~ i~- ~~-...Nil" rm~"°(7) ~ -CH=N 3,~ (NNO) ~ J
~_ ~!7)~= O
' ,~ N ~(7)C-OH
,
A,O,~ -
=
313.(NNO)
3C.(NOO)
\-~
N
- C H = N
..3B[( N NO )
3C. ( NOO )
Fig. 3. Possible flexidentate behaviours of salicylidene 8quinoloyl hydrazoneschiff base (both in keto and enot form).
62
R. L. DUTTA and A. K. SARKAR
through the formation of seven and six membered ring. If the quinoline nitrogen bonds the metal as also the amide -I (C-O) group via a six membered ring (Fig. 3c), then it is not possible for the hydrazine nitrogen to bond the metal. The phenolic oxygen may, however, be attached to the metal ion via a rather unstable nine membered ring (Fig. 3C). In the enol forms (Figs. 3A' and 3B'), the ligand may function as an (NNO) donor having six membered and seven membered rings. The donor centres are the quinoline nitrogen atom, one of the hydrazine nitrogen and the phenolic oxygen. So far several patterns of behaviour have been noticed. However, if we disregard the possibility of the 8-quinoline nitrogen coming into play as a donor, the ligand then will effectively behave like salicylidene benzoyl hydrazone [Fig. I (IV)].
2. Neutral tridentate ( ONO) behaviour (a) Modes o[ attachment of the three ligands. Salicylidene 2-picoloyl hydrazone (H2L) reacts with NiCI2, COC12 and MnCI2 to give complexes of the type [Ni(H2L)2] C12, [Co(H2L)2] C12 and [Mn(H2L)2] C12. These complexes are bivalent electrolytes [8] in methanol (Table 3) indicating that the two chloride anions are not co-ordinated to the metal ions. The neutral behavior of these ligands compared to the monobasic[3] or dibasic[4, 5], character of salicylidene benzoyl hydrazone is probably a reflection of the overall influence that the basic pyridine nitrogen has on the molecule. The IR spectra (Table 4) of these three complexes are almost superimposable indicating the same sterochemistry. The free ligand (H2L) has a stretching frequency of
Table 3. Magnetic moment and conductibity data of complexes
~
Compounds M
R'
R"
R"'
X
n
| B.M. at r o o m temperature
M o l a r conduetanee o h m s - l e m 2 m o l e -I at 25°C (Solvent)
I. CM(R,-c0-~-~-~-R")~Tx2~2o R"t Ni
2-pyridlne
2-OHc6H 4
H
Cl
-
3.2
1 8 0 (methanol)
Co
"
"
"
"
Mn
"
"
"
"
Ni
"
"
CH 3
"
1
3.1
175 ( m e t h a n o l )
Co
"
"
"
"
"
4.6
167
"
H
C1
-
3.1
193
"
"
"
"
"
-
4.47
168
"
Co
"
"
C~ 3
"
-
4.52
Insoluble
Ni
"
"
"
"
-
3 • 13
"
H
"
1
3.08
180 (methanol)
"
~I 3
"
1
4.8
Insoluble
H
Cl
4.5
49 (methanol)
Br
4.5
20
Ni
2-quinoline
Co
8-qu~noline
N~
Co
"
2. / - M ( R ' - C O - N H - N = C - R " ) X
4.6
158
5 •58
I nsoluble
"
"
"
7
R" t Co
8-~ulnoline
o-0C6H 4
Co
"
"
Pd
C~5
"
3.
"
Cl
Diamagnetic
o-0C~4
H
-
2
5.74
"
"
-
"
4.8
"
5 (nlt romethene)
L-M(a'-co-~-N~-R") ~20 R-f
Mn Co
~-quinollne "
Insoluble "
4 CM(R '-CO-~-~-C-m')X_TX l Pd
~- p y r i d i n e
o-OHC6H 4
H
CI
Diamagnetic
15 (pyridine)
~. CMO(R'-C--N-.-~-R"~(~zO)~20 ~V
2-pyridine
V
2-qulnoline
R" ' R - O C 6H 4 "
e. Z - - ~ ( R ' - C O - ~ - N = ~ - R " )
V
R-quinoline
o-0C~4
H
1
1.62
20 (methanol)
"
1
1.4
18
1
Diamagnetic
Insoluble
"
(O~)~_7~zO
H
-
A study of some transition metal complexes of salicylidene 2-picoloyl hydrozone schiff base and related ligands Table 4. Spectral data of the ligands and their metal complexes Compounds R '
~m-H ~mlde I ~C-N ~M-X ~M--O
R"
R" '
X
R '-CO -NH - N = C - R "
2-pyr~dine
o-OHC6H 4
3520
1670
1620
-
"
CH 3
3333
1690
1600
-
"
H
3300
168:2
1600
-
" 2-qulnollne " 8-qulnoline " Benzene
H
-
"
CH 3
3300
1675
1595
"
H
-
3440
1660
1620
"
CH 3
-
3400
1660
1600
-
"
H
325'0
167f
1600
-
3262
1650
1613
-
L-N~ (R'-c0-~-~ =?-R ,,)e_7x2 2-pyrldlne
o-OHC6H 4
" 2-qulnollne "
8 - q u l n o l l ne
H
Cl
"
CH 3
CI
3390
1613
1590
"
H
CI
3400
1625
1595
"
CH 3
CI
Broad band
"
H
CI
163C
1590
B road band
1610
1600
ECo(R'-C0-~H-~:C-R") J x 2 R" i 2-pyrldlne
o-OHC6H 4
" 2-qulnollne " 8-qulnoline
H
CI
3257
1639
1600
"
CH 3
C1
337B
1613
1600
"
H
C1
3400
1615
1595
"
CH 3
C1
Broad band
1636
1590
-
"
CH 3
C1
3120
1620
1590
-
3247
1626
1600
L-H~(B'-CO-~-~=C-B") i S._7X2 2-pyrldine
o-OHC6H 4
H
CI
CCO(B'-CO-NH-N--C-R")X_7 l R" t R-qulnollne "
o-OC 6B 4 "
H
C1
3400-3500b
1609
1590
290
H
Br
"
1607
1590
260
R" t 9-oul n o l l n e
o-0C6H 4
H
Broad band
1612
1602
1610
1600
Broad band
1600
1560
-
Broad band at :9400
1595
1570
320
/-co (R '-co-,~H-~ =c-R") 2_7H2o R"
R-oulnol~ne
o-OC 6H 4
t
H
-
/-Ni( R'-CO-~,'H =C-R" ) R- I
I
Benzene
o_-OC 6H 4
H
-
Z-m (R' - c o - ~ -N=C-R" )c1_7 Benzene
o-OC 6H 4
H
CI
Contd.
6]
R. L. DUTTA and A. K. SARKAR Table 4. (Contd) Compounds R'
4N-H N"'
~Amide 14C=N
~M-X
4 M=O
X
L-Pd(R'-CO-N~-N:?-R")Clz_7 2-pyrldine
R-OHC~4
H
CI
-
1615
1605
310 365
1625
1610
-
-
1600
-
965
-
1590
-
955
~-VO(R'-CO-NH-N=C-R")(OH)2_TH20 R.t 8-quinol~ne
~-OC6H4
H
3300-3400b
960
L-VO(R'-C=N-N--~I-R")SH20_7 OR"' 2-pyr~dlne
~-OC6H 4
H
2-quiniline
"
H
Broad band "
b
=
broad
the amide-I (C-O) band[9] at 1670cm -~ and of the azomethine (C-N) group[10] at 1620cm -~. In all the three complexes, there is a shift of both the bands to lower frequencies (for C-O band 20--40cm ' and for C-N band 10-20cm -~) indicating that the ligand is attached to the metal ion in its ketoform with the amideI(C-O) group being co-ordinated to the metal ion. Our models show that if (C-O) and (C-N) are attached to the metal ion, then there is no scope for the ring nitrogen to be co-ordinated (see Fig. 2A). The IR spectral data of the complexes,[M(Hy)2] C12 and [M(H2L")2] C12 (where M = Ni(II), Co(II); H2L' and H2L" are salicylidene 2-quinoloyl hydrazone and salicylidene 8-quinoyl hydrazone respectively) show that the ligands are co-ordinated to the metal ions via the amide (C-O) oxygen and azomethine (C-N) nitrogen. Since the position of the ring nitrogen atom in the 2-picoloyl ligand and the 2-quinoloyl ligand are comparable, hence the 2-quinoline nitrogen is again not co-ordinated (see Fig. 2A). If the 8-quinoline nitrogen atom is co-ordinated, then the model predicts a nine membered ring (Fig. 3C) in order to span the phenolic oxygen. This is rather improbable and there is also a clear indication of attachment of the azomethine group (lowering of C-N band 15 cm-'). (b) Magnetic moment, conductivity and electronic
spectra of bis(salicylidene 2-picoloyll2-quinoloyl/8quinoloyl hydrazone) Ni(II) halide complexes. The Ni(II) complexes are green to yellowish green (Table 2) and are paramagnetic (/~ = 3.1-3.2 BM, Table 3) which suggests octahedral geometry. [l l]. The electronic spectra of most of the complexes are ill resolved (Table 5). Of the several complexes for which mull spectra have been obtained, one, namely, bis (salicylidene 8-quinoloyl hydrazone) Ni(II) chloride gives the three expected absorption bands at 11.2, 17.3 and 28.5 kK[12]. These three bands may be assigned to 3A2g~3T2g(/),);3A2~ 3 T,g(/)2); and 3A2g --)3 I"1~(P)(u3) respectively. The v2[v,, ratio ~1.54 is in conformity with octahedral geometry[13, 14]. It is of interest to note that an attempted synthesis of [Ni(H2L'")2]CI2 (where H2L' ' = salicylidene benzoyl hydrazor.e) via an interaction of anhy-
drous NiC12 and H2L'" led not to the desired product but to [Ni(HL'")2]. This complex was originally synthesised by Sacconi[l] using [Ni(salh] (salH=salicylaldehyde) and benzoyl hydrazide. Formation of [Ni(HL'")2] is a manifestation of the preponderance of the monobasic tridentate behaviour of H2L'". (c) Electronic spectra and magnetic moment o[ bis(salicylidene 2-picoloyl/2-quinoloyl hydrazone) Co(II) halide complexes. The Co(II) complexes have magnetic moments (/x=4.5-4.6BM), on the lower side of the octahedral Co(II) range[15]. The electronic spectra (Table 5) of the Co(lI) complexes are rather well resolved and show bands at 8-8.7 kK, 16-16.3 kK and near 17-18.2kK. In octahedral symmetry[16], these bands may be assigned to the transitions 4T,~ ~4T2~(v0; 4T,e ~4A2~(/)2; and 4T,~ ~4T,(P)(v3) respectively. The ratios of v2//),, are in the range (1.82-2.2) as is expected for Co(II) octahedral stereochemistry[16, 17]. Assuming the first absorption band in our complexes as v~ = 8 Dq, the calculated v2 (=18 Dq) is consistent with the second band observed in these complexes. The molar conductance (AM) values for the Co(II) complexes (Table 3) indicate their bi-univalent electrolytic character. (d) Bis(salicylidene 2-picoloyl hydrazone) Mn(II) chloride. Only one such complex namely [Mn(H2L)2] 02 has been obtained in crystalline form. Attempts to obtain corresponding complexes with H2L' and H2L" produced only slimy products which are difficult to filter. The experimental moment (# = 5.58 BM) is, however below the spin only moment. A conductance measurement was not possible due to poor solubility in suitable solvents.
3. Monobasic tridentate ( ONO) behaviour Such behaviour has been observed with salicylidene 8-quinolyl hydrazone ligand but not as yet with salicylidene 2-picoloyl/2-quinoloyl hydrazone ligands. (a). Chloromono (salicylidenato 8-quinoloyl hydrazone) Co(II). Co(II) chloride and Co(II) bromide react with salicylidene 8-quinoloyl hydrazone to give light green complexes of the type [Co(HL")X]n (where X = CI, Br and H2L" = salicylidene 8-quinoloyl hydrazone). The IR spectra of the ligand show characteristic sharp ab-
A study of some transition metal complexes of salicylidene 2-picoloyl hydrazone schiff base and related ligands
could be suggested. The magnetic moment (# 4.5 BM) rules out a square planar structure. The stretching frequency of ~,(Co-Cl) and t,(Co--Br) for these corn.. plexes are =29(I and 260 cm-' respectively (Table 4). It is pertinent to mention that the stretching frequency[18] of v(Co-CI) and t,(Co--Br) of monomeric octahedral Co(II) complexes are around 230cm -~ and =200cm ' respectively and for tetrahedral Co(II) complexes t,(Co(Cl) and v(Co--Br) are =320 cm-Z and =270 cm ' respectively. A light green colour is less likely for a tetrahedral structure. The electronic spectra (in Nujol mull) resemble (Table 5) a six-co-ordinate polymeric octahedral structure rather than a tetrahedral or a five co-ordinate one (Section VI). (b) Bis (salicylidenato 8-quinoloyl hydrazone) Mn(II) and Co(II). Mn(lI) chloride reacts with the 8-quinoloyl Iigand to give a light red coloured [Mn(HL")j complex (where H2L" = salicylidene 8-quinoloyl hydrazone). Due to poor solubility in common organic solvents, conductance measurement and molecular weight determinations were not possible. Comparison of the IR spectra of the ligand and complex shows a lowering in the frequency of both the bands
sorption bands at 3440, 1660 and 1620cm-' (Table 4). These bands are assigned to u(N-H), ~,(C-O) and v(C-N) stretches respectively. In the light green Co(II) complexes, there is a distinct shift of C-O and C-N bands to lower frequencies (for C-O, A~,=45cm-' and C-N, A~,~-10cm '), indicating that the ligand is attached to the metal ion in its keto form and co-ordination takes place through (C-N) nitrogen and (C-O) oxygen atom. It is obvious that electroneutrality is achieved through the deprotonation of the phenolic -OH group. The models showed that if the (C-O) and (C-N) groups are attached, to the metal ion then there is no possibility for the ring nitrogen to be co-ordinated. These complexes are soluble only in donor solvents such as pyridine, dimethylsulfoxide etc. The conductivity in methanol at 10-4M gives a value -15-20ohm 'cm2mol J (Table 3). The magnetic moments (Table 3) of the complexes are on the border line of tetrahedral and octahedral complexes. In fact several structures, namely, a four co-ordinate square planar, a tetrahedral, a five co-ordinate dimeric structure with bridging oxygen and terminal X, and also a polymeric halogen-bridged and oxygen-bridged structures
=
Table 5. Electronic spectral data for Co(lI) and Ni(lI) chelates Chelates
State R'
R"
R"'
X
Absorption bands i n k K
n
d-N~ (R'-CO-~-N=C-R")2_TX2.nH20 o-OHC6H 4
H
CI
2-quinollne
"
"
"
,,
28.5
,,
CH3
"
,,
27.7
"
H
"
"
28..5
R-qulnollne
-
Reflectance
2-Pyrldlne
,,
1
26.6 ~ ) 7 16.9
ii. Benzene
o-OC6H 4
H
-
"
2
:L'
"~
28.26 ~ 3 17.4
~2
io.8 ~i
Z-c o( R '-CO-~-N~-R")_Tx 2.nil20 R" ! ~-pyridlne
o-OHC6H a
H
CI
"
H
"
-
Reflectance
_% 18.1 16.0
,~'3 "*)2
8.3 ~,
9-qu:l n o l l n e
18.0 (sh) 16.0 (sh) 16.0
CH 3
(sh)
18.1 (sh) ~-aul nollne
"
H
"
I
H
CI
-
"
23.Z 16.13
H
Br
-
"
23.5 16.2 8.5
2
Reflectance
18.02 16.00
16.0 8.7
~-Co (R '-CO-N~I-N:C-R") X 7 R" t ~-~ i n o l l n e
"
o-OC6H 4
"
/ - C r ( R '-CO -NH - N = C - R " ) 232I[20 I
q-oulnollne
JINC
"~oJ~ No I--E
o-OC6R 4
H
-
65
(sh) (sh)
66
R. L. DUTTA and A. K. SARKAR
(C-O) and C-N for the complex (for C-O band, Av = 30cm -~ and for C-N, Av-~7cm -~ (Table 4). It is concluded that the ligand reacts with Mn(II) in its keto form and co-ordination takes place via (C-O) oxygen and (CN) nitrogen atom. Electroneutrality is achieved through deprotonation of the phenolic OH group. The magnetic moment (# = 5.7 BM) and electronic spectra of Mn(II) are not indicative of its stereochemistry. However, since the ligand suffers deprotonation of its phenolic -OH group, we suggest that the complex is pseudo-octahedral and that the ligand functions as tridentate monobasic (ONO) form. We have not so far succeeded in isolating products like [NI(HL)2], [Ni(HL')2] and [Ni(HL")2] while [Ni(HL'")2] is well characterised. This inner metallic complex exhibits bands at 10.8, 17.4 and 23.26 kK. It appears that the ligand H2L"' is weaker (~ = 10Dq= 10.8kK) than the neutral H2L" (v~ = 10 Dq = 11.2 kK) (see Table 5). The IR spectral data of the deep yellow complex, bis(salicylidenato 8-quinoloyl hydrazone) Co(II), shows that the ligand is attached to the Co(II) via (C-N) nitrogen, (C-O) oxygen and phenolic oxygen atom (Table 4). The deprotonation takes place from the phenolic hydrogen. A pseudo-octahedral structure is suggested from the magnetic measurement[15] and electronic spectrum (Table 5). Due to poor solubility in common organic solvents, a conductance determination was not possible. (c) Oxo-dihydroxo mono (salicylidenato 8-quinoloyl hydrazone) vanadium(V) monohydrate. The 8-quinoloyl ligand (H2L") reacts with oxovanadium (iv) sulphate in a way which is distinctly different from the reaction of the other two ligands. While the 2-picoloyl and the 2quinoloyl ligands provide dark red, paramagnetic samples, the 8-quinoloyl ligand gives a greenish brown diamagnetic material, [VO(HL")(OH)2]-H20. Its IR spectrum shows that the amide-I(C-O) band is retained although lowered in frequency by =25 cm -~ (Table 4). It also reveals a strong and very broad hydroxyl band around 3350-3450cm -~. The co-ordination of the azomethine group is also indicated by a small shift Av = 10 cm ~ of the C-N stretch compared to that in the free ligand. Thermal analysis shows a loss of 5% (required 4.4% for one H20). The complex then proceeds to decompose further in a slow step up to 220°C (total loss at this stage being 9.9%). It rapidly decomposes to give V205 at 1000°C (total loss--80%; required---77.8%). Possibly the V(IV) is oxidized in the complex.
cules of water. In the oven at ll0°C, [VO(L)(H20)2] H20, loses one H20, while a thermogravimetric study reveals two slightly overlapping water losses--the first a loss of 6.2% over the temperature range 500110°C and the second a loss of 7.5% over the range 110-280°C. The total loss is 13.7%, while the calculated loss for three molecules of water is 15%. The complexes are paramagnetic (Table 3). Unfortunately only one absorption band around 20-23 kK is identifiable.
5. Neutral bidentate (ON) behaviour of salicylidene 2-picoloyl hydrazone The behaviour of salicylidene benzoyl hydrazone (H2L'") and salicylidene 2-picoloyl hydrazone (H2L) towards Pd(II) is quite different. The former ligand suffers partial deprotonation to give [Pd(HL'")CI]. The IR spectral data for this complex shows that there is a distinct shift of both the C-O and C-N bands to lower frequency (Table 4) from the positions for the free ligand. The molar conductance in nitromethane (5ohm ~cm2mole-') indicate that the compound is nonelectrolytic. The Pd-CI stretch in the far-IR region is found at 320cm-'[20]. A monomeric square planar complex with H2L'" behaving as a monobasic tridentate ligand is thus suggested. Salicylidene 2-picoloyl hydrazone (H2L), being less acidic, reacts with chloropalladite ion to produce [Pd(H2L)CI2]. The IR spectral data (Table 4) indicate that there is a shift of both the C-O and C-N bands (for C-O, A~,=55cm-~; and for C-N, Av=15cm -t) to lower frequencies, indicating attachment through C-O and CN. Two sharp bands at 310 and 365 cm -z are found in the far-IR region. These bands are assigned to Pd-CI stretches[21,22]. The molar conductance value in pyridine (AM=15fl-~cm2mol) shows some slight dissociation in pyridine. A five co-ordinate, nonelectrolytic, monomeric structure is not very likely because the few such complexes known for palladium (II) are with ligands having soft donors like As, P,[23]. The obvious conclusion is that the ligand H2L functions as a bidentate NO donor.
6. Exceptional behaviour of salicylidene 8-quinoloyl hydrazone ligand
The 2-picoloyl and the 2-quinoloyl ligands behave alike while the 8-quinoloyl ligand shows exceptional behaviour. for instance in its Co(II) complexes [Co(HL")X],(X = CI, Br). The Co(II) complexes of the other two ligands conform to the composition [Co(H2Lh]X2 and 4. Dibasic tridentate (ONO) behaviour. Oxovanadium [Co(H2L'h]X2. In none of these complexes, is there any (IV) complexes o[ salicylidene 2-picoloyl/2-quinoloyl evidence in favour of participation of the heterocyclic hydrazone nitrogen. A comparison of the acid/base character For the oxovanadium (IV) complexes of 2-picoloyl and 2-quinoloyl ligands, (VO(L)(H20)2] H20 and [VO(L') (H20)2] H20, (H2L = salicylidene 2-picoloyl hydrazone; H2L'= salicylidene 2-quinoloyl hydrazone), the IR spectra reveal a strong (V-O) stretch[19] around 955%5cm-L There is no amide-I(C-O) band found at 1670cm -~ for the 2-picoloyl ligand and at 1675 cm -~ for o the 2-quinoloyl ligand. There is also the expected lowering of the C-N band (Av = 13cm ~ for the 2-picoloyl ligand and Av = 10 crn -2 for the 2-quinoloyl ligand). We o i o conclude that co-ordination takes place through the (Cx × N) nitrogen and that the ligands interact with the oxovanadium (IV) in the enol form and lose, in the process, both the enolic hydrogen and the phenolic hydrogen. Elemental analysis (V, N, H20) fit with three moleFig. 4.
,,\ study of some transition metal complexes of salicylidene 2-picoloyl hydrazone schiff base and related ligands [24, 25] of the heterocylic carboxylic acids (2picolinic acid, Pka = 5.1; 2-quinaldinic acid, PkA = 4.% and quinoline 8-carboxylic acid PkA = 7.2; see benzoic acid, PkA = 4.17) shows that quinoline 8-carboxylic acid is the weakest while the benzoic acid is the strongest acid among the four. It is, therefore, not surprising that while salicylidene benzoyl hydrazone has so far not shown any neutral tridentate (ONO) behaviour, all the three ligands under investigations, show neutral (ONO) behaviour under certain conditions. For the green [Co/HL"iX] n(X = CI, Bri, it is proposed that the introduction of one HL" around the Co(II) absorbs much of the electron-accepting power of the metal, compared to, say Ni(lIt, so that it is not possible to introduce a second molecule. Instead, to satisfy octahedral geometry, the metal ion responds through polymerisation via bridging bah)gen and bridging (ON()) groups (Fig. 4). It is fascinating to note that the ligand derived from the interaction of the 8-quinoloyl hydrazide and ohydroxyacetophenone does not give the polymeric light green Co(II) complexes. Instead, we get bis(ligand) Co(II) halides. It is obvious that the inductive effect of lhe ~CH, group makes the phenolic (-OH)less acidic, thus preventing deprotonation. That this 8-quinoloyl ligand is unique among the three heterocyclic substituted ligands (H~I,, H~L' and HzL") so for studied is also indicated by its reaction towards oxovanadium (IV) t,~ produce ~ diamagnetic possibly quinquevalent oxo~anadium (V) complex. This behaviour may also be credited to its comparatively weaker acid, i.e. stronger b~sic character.
REFFRENCES
'. L. Sacconi. J. 4m. Chem. Soc. 74, 4503 (1952). 2 I El Sayed and M. F lsakander, J. lnorg. Nucl. Chem. 33, 435 (1971).
67
3. M. F. Isakander and L. El. Sayed, lnorg. ('him. Acta 16, 147 (1976). 4. M. F. lskander and A. M, El. Aggan, lnorg. Chim. Acta 14, 167, (1975). 5. R. L. Dutta and S. P. Banerjee, J. Indian Chem. Soe. 5l, 497, (1974~. 6. C. Pelizzi and G. Pelizzi, lnor~. ('him. Acta 18, 139, {1976). 7, A. H. Cook, I M. Heilbron and L. Steger, J. Chem. Soe. 413 (1943). 8. W. J. Geary, Co-ord. Chem. Rev. 7, 1-81 H971), 9. M. Mashima, Bull. Chem. Soc. Japan 35. 1882 11%2): ~, 210 (1%3). I0. L. J. Bellamy, The IR Spectra of Complex Molecule~, 3rd Edn. Methuen, London (1%6). l l. R. B. Heslop and P. L. Robinson, Inorganic ('hemi~try, p. 702. Elsevier, New York, (1%7). 12. A, B. P. Lever, Inorganic Eleetnmic Spectroscopy, p. 333. Elsevier, Amslerdam 11%8). 13. D. W. Meek. R. S. Drago and T. S. Piper, lno(¢ ('hem. I. 285 ~1962). 14. L. Sacconi, Transition Metal Chemisto' (Edited by R. L. Carlin, Vol. 4, p. 212. Marcel Decker, New York (1%81. 15. E. K. Barefiehl, D. H. Busch and S. M. Nelson, Quart. Rev. 22, 457 {1%8). 16. R. L. Carlin, Transition Metal Chemistry (Edited by R. L. Carlin, Vol. 1, p. 320. Marcel Decker, New York, {1%5). 17. A. D. Liehr, J. Phys. Chem. 67, 1314 (1%3). 18. D. A. Baldwin, A. B. P. Lever and R. V. Parish, lnom. ('hem. 8, 107, (1%9t. 19. M. Plytzanopoulos, G. Pneumatikakis, N. Hadjuliadis and D. Katakis, J. lnor~'. Nucl, Chem. 39, %5 (1977). 20. Robin J. H. C~ark and C. S. Williams, lno(~,. Chem. 4, 3~(t (1965). 21. L. Caglioti, L. Cattalini, M. Ghedini, F. Gasparrini and P. A. Vigato, J. Chem. Soc. Dalton 514 (1972). 22. R. A. Walton, ~pectmchim. Acta 21, 1795, (1%5). 23. C. Furlani, Coord. Chem. Rev. 3, 141-167 (1%8). 24. W. R. Maxwell and J. R. Partington, Trans. Faraday Soc. 33, 670, (1937). 25. R. C. Elderfield and M. Siegel, J. Am. Chem. Soe. 73, 5622, (1951).