Coordination compounds of hydrazine derivatives with transition metals—VII

J. inorg, nucl. Chem., 1974, Vol. 36, pp. 1739 1743. Pergamon Press. Printed in Great Britain.

COORDINATION COMPOUNDS OF HYDRAZINE DERIVATIVES WITH TRANSITION METALS--VII METAL(II) COMPLEXES WITH HYDRAZINE S-METHYL DITH1OCARBOXYLATE SCHIFF BASES AND THEIR PYRIDINE ADDUCTS L. EL-SAYED, M. F. 1SKANDER and A. EL-TOUKHY Chemistry Department, Faculty of Science, Alexandria University, Egypt

(Receit'cd 18 May 1973) Abstract--Metal(ll) chelates of general formula M(RtR2C=N Cu(H);

N C S S C H 3 ) 2 (M:Ni(II), Co(ll) and R 1 = R 2 = C H s ; R 1, R 2 = C s H F o a n d R 1 = C H 3, R 2 = C 6 H s ) w e r e p r e p a r e d a n d i n v e s t i g a t e d .

Magnetic and spectral data indicated square planar Ni(ll) complexes while Co(ll) afforded tetrahedral complexes. All the Cu(lI) chelates probably possessed a dimeric pentacoordinate geometry. The reaction of pyridine with the bis metal (II) complexes were discussed. Monopyridinate adducts were isolated with the bis (N-isopropylidene hydrazine-S-methyldithiocarboxylate) cobalt (II) and nickel (11) chelates.

INTRODUCTION

studies on the coordination properties of hydrazine S-methyl dithiocarboxylate have shown that the molecule may act either as a neutral or monobasic bidentate ligand [ 1, 2]. The Schiff bases derived from the condensation of the above mentioned base with some aromatic and heterocyclic aldehydes were found to behave as monobasic bidentate ligands, giving bis neutral complexes with nickel(ll) salts[31. These complexes possess a square planar structure with the basic coordination unit NiN2S2. Interaction of pyridine with such complexes afforded either a five-coordinate monoadduct or a six-coordinate biadduct[3]. The Lewis base acceptor properties of complexes with MS,,[4-6] and MO417-11] chromophores were extensively studied but little has been reported on complexes with the MN2S 2 chromophore. Accordingly bis con> plexes of Schiff bases RECENTLY,

R~C

= N - NH

R 2/ (I) l(a).

R I = R 2 =CH

C - SCH 3 II s 3

I(b). R l, R 2 = C5HI0 l(c). R 1 = CH3, R z =

C6H 5

(I, a, b and c) with Ni(II), Co(ll) and Cu(II) ions were prepared in this work and their interactions with pyridine will be discussed. RESULTS AND D I S C U S S I O N

The Schiff bases (la, b and c) react with nickel(ll), cobalt(II) and copper(II) acetates in a 2:1 molar ratio

yielding the bis neutral inner chelates M(L)2, where/_ refers to the deprotonated ligand. The analytical data for the complexes isolated are given in Table 1. They are all readily soluble in benzene, chloroform, carbon tetrachloride and to some extent in ethanol. The i.r. spectra of the bis neutral metal(It) chelates lack any absorption band corresponding to the N - H stretch when compared to the spectra of the parent ligands. The band due to - - C = N - - located at 1620 _ 5 c m - 1 as well as the four bands at about 1100, 1020, 970 and 850 cm-1 attributed to - - N - - C S S C H 3 residueEl], are shifted to lower frequencies in the metal complexes. Elemental and i.r. spectral data suggest that the ligands are monobasic and bidentate in the neutral complexes, coordinating to the central metal ion via the azomethine nitrogen and the thiol sulphur atom.

Stereochemistry of the bis metal(II) complexes The magnetic and electronic spectral data on the bis neutral nickel(It) and cobaltll l) complexes are given in Tables 1 and 2. Some representative spectra are shown in Figs. 1 and 2. The diamagnetism of all bis nickel{II) chelates suggests the singlet tAg ground state. Their electronic spectra in a nujol mull, benzene and methanol are identical and consistent with a square planar structure (Fig. 1). Assuming Dzh symmetry for these complexes the bands at about 15 and 18 kK may be assigned to ~Blg~-tA~ and ~Bag~ lAg transitions respectively while the band at 21 kK may be related to the 1Au +-- t A~ transition E12]. The solid bis cobalt(II) complexes (v) and (viii) are blue in colour and appear to have a tetrahedral

1739

1740

L. EL-SAYED,

M. F. ISKANDERand A. EL-TOUKHY

30~~\~ \\ k\

I

(a]

- - ~

~,\

/ ,,"

~/

2'0

,\

f/-"..'x

//"

",,,,

1.0

f ~'i,

i

\',\

x,,

(bl

\',

4

(b) 2C

\. J ' P ' / " \ .

! \

"~.. 3 " x \

1

\, x.~.. \ ".\

2Ù

"\

"x

' \ ',,,',, 400

.\ I

1

I

500

600

7OO

I

500

8OO

I

700

I

800

]

900

-~-

9OO

Wavelength, ml~

Fig. 1. The electronic spectra of Ni(RXR2C = N--NCSSCH3)2: (a) 1--R 1 = R 2 - CH a in benzene; 2 R ~ = R 2 = C H 3 in pyridine; (b) I - - R I = C H 3, R 2 = C6H5 in benzene; 2--R ~ = C H 3, R 2 = C 6 H 5 in pyridine: 3--R 1 = C H 3 , R 2 = C 6 H 5 in nujol mull. stereochemistry on the bases of their magnetic moments (Table 1) and electronic spectral13] (Table 2). The solution spectra in benzene and methanol show the same band maxima and intensities, indicating retention of the tetrahedral environment in these solutions. The bis cobalt(ll) complex with the acetophenone derivative (vii) is, however, dirty brown in the solid state, giving a deep red benzene solution. Its nujol mull and solution spectra in benzene are identical and similar to those of!v) and (viii), but lack the detail in the 17.0 kK region. Most probably, compound (vii) has the Co(ll)

Fig. 2. The electronic spectra of Co(RIR2C = N--NCSSCH3)2: 1--R 1, R 2 = cyclohexyl in nujol mull: 2 R 1 = R E = C H 3 in benzene: 3--R 1 = R 2 = C H 3 in pyridine: 4--R 1 = C H 3, R 2 = C 6 H 5 in benzene: 5--R 1 = C H 3 , R 2 = C 6 H 5 in pyridine. ion in a highly distorted tetrahedral environment due to the presence of the bulky C6H 5 group. The room temperature magnetic measurements reveal that the bis copper(ll) complexes possess subnormal magnetic moments, suggesting some sort of molecular association. The electronic spectra of both solid and benzene solution (Table 2) show a broad band centered at 16.5 kK with a well resolved shoulder at the lower energy side. The position of the bands as well as their intensities are not consistent with tetrahedral or octahedral copper(ll) complexes but may be related to the spectra reported for five coordinate geometry[14, 15]. This structure could be achieved through dimerization, with sulphur atoms acting as bridges.

Table 1. Analytical and magnetic data of the metal(II) complexes

",, Metal Compound No. i ii iii iv

R1

R2

CH 3

CH 3

CH 3

CH 3

CH 3 C6H s CsHt0

V

CH 3

vi vii viii

CH 3

CH 3

CH 3 CH 3 CH 5 CsH~o

ix

CH 3

CH 3

X

CH 3

C6H 5

xi

C5H10

Formula

1000

Wavelength, rn/s

"<~ ......

I'~-~

B

600

Colour

Calcd

Found

",, Sulphur Calcd

Found

# ~r (°K) B.M.

33.64 27-86 25-37 27.80

Ni(L)2 Ni(L)2. Py Ni(L)2 Ni(LI2

Violet Green Green Violet

15.40 12.75 11.61 12.72

15.42 12-80 11.68 13.23

33.32 27-76 25.21 27.90

diamag. 3.23(295) diamag. diamag.

Co(L) 2 Co(L)2. Py COIL)2 Co(L)2

Green Gray-brown Brown Blue

15-44 12-79 11.65 12.76

15.50 3 3 . 6 2 3 3 . 2 5 12-80 2 7 . 8 4 2 7 . 5 1 11.92 2 5 . 3 6 2 4 . 9 0 13.08 2 7 . 7 8 2 7 . 6 0

4.80(295) 4.34(296) 4.40(295) 4.77(296)

Cu(L) 2 Cu(L) 2 Cu(L)2

Green Green Green

16-45 12.45 13.63

16.32 12.80 13.52

1.58(299) 1.72(298) 1.60(293)

33.22 25.13 27.50

33.02 25.20 27.32

1741

Coordination compounds of hydrazine derivatives Dimerization of copper complexes with sulphur containing ligands are well known [ 16, 171. The formation of dimers in the case of coppe.r(ll) chelates with S-carboxydiethyl dithiocarbamic acid and diacetyl bis thio-semi carbazone was suggested to account for their ESR spectral 161. Moreover X-ray structural analysis of the dimeric copper(I1) dithiocarbamate complexes have shown that the copper( 1I) ion is in a trigonal bipyramidal ordistortedsquarepyramidalenvironmentrl7].Accordingly the dimeric structure (II) may be adopted for the copper(l1) chelates reported in the present work. The subnormal susceptibilities of these chelates are in agreement with such a structure.

The solution spectra in pyridine of all the bis metal (II) complexes were recorded. The results are shown in Table 2. Electronic R’ CH,

RZ CH,

CSH,O

CH,

CH3

C,H,

CH,

CSHIO

Compound NW,

Ni(L),

NiCL),

Co(L),

Co(L),

CH,

C,H,

Co(L),

CH,

CH,

Cu(L),

CsH,,

CH,

(3,

sh = shoulder;

Cu(L),

cuw,

State Mull Benzene Acetone Pyridine Mull Benzene Pyridine Mull Benzene Methanol Pyridine Mull Benzene Acetone Pyridine Mull Benzene Pyridine Mull Benzene Pyridine Mull Benzene Acetone Pyridine Mull Benzene Pyridine Mull Benzene Methanol Pyridine

bsh = broad

shoulder

spectra

Band maxima -27.4 27.8(5450), 27.8(5760) 27+3(2890), 27.5 27~5(5500) 27.5(3000), 25.0 26,3(7400). 26.6(6760), 26.3(7300). 23.3s.h. 22,9sh(340), 23,2sh(335) 23,8sh(760) 24,lsh. 23.9sh. 23.8sh. 25.0,

24. I 23.0(2000), 23.3(2340). 21.5(1415), 23&h. 23.1(2000), 21.4(1420). 22.7, 22,7(2200), 22.9( 1850), 23.8(2628),

Table 2. The spectra in pyridine of bis nickel(l1) and cobalt( II) complexes with N-isopropylideneand Ncyclohexylidene-hydrazine-S-methyl-dithiocarboxylates are completely different from their mull or solution spectra in benzene, implying a strong interaction. The observed spectral characteristics are similar to those reported for Ni(fI)[l&201 and Co(II)[21] complexes in five-coordinate geometry. Crystallization of nickel(I1) or cobalt(I1) complexes with the acetone derivative (i and v) from pyridine solutions afforded stable monopyridinate adducts (ii and iv). Magnetic measurements (Table 1) indicated a high spin type. Differential thermal analysis showed an endothermic peak at 175 and 100°C for the nickel(I1) and cobalt(I1) adducts respectively. Complete depyridination gave the original bis neutral complexes with a loss in weight corresponding to one pyridine molecule. No stable solid adducts were isolated with the analogous N-cyclohexylidene derivative. The mull spectra of the solid monoadducts could not be made due to rapid loss of pyridine upon grinding. However, their solution spectra in pyridine exclude the formation of a biadduct. Molecular models show that the most favourable symmetry for a monoadduct of either a square planar or tetrahedral species is a of bis metal(I1) complexes

kK

(1:mO,arfor solution)

.___. 20.8 20.4(215) 22.7(678), 20.5 22.5(670), 17.9 I X.2(270) 17.8(225), 17.8(240) 17.9 17.9(225), l&2(172), l&9(75), 19.4sh,

18.2, 17.9(340) l&%h(112) 21.3sh 20.0( 1540). 19.6( 1690), 19.3(918), 17.1 16.8( 1420), 17.0(s.h)(600) 18,9sh, 16.7(1425), 16.8(1 loo), 17.0(865),

18.9 18.9(250) l&9(225), 14.7(90) 18.7 19.2(248) 14.7(100) 16.9sh

I6.3sh 15,2sh(70) I5.2sh(65)

14.9sh

17.7sh. 17.2(16$)

16,4sh,

13.9sh

IS.9 I5.9(553) I5.9(438) 14,5bsh(24) 17.2 17.0(390), I7.3(90), 14.5 14.5sh 14.5sh 13.7sh 14.3(770), 15.1sh 16.0(500), 12GG.h 12.5sh( 180) 12.5sh( I 10) 15.7sh

13.7sh. I3.7sh. 13.9sh,

IO.0 10.0

16.35sh( 12) 16.7 16.7(382), 16.7(306), 17.24(95), 18.0 17.9(230). 18.9(80), 15.9 157(380) 16.9( 137) 18.2 16.4( 1450). 16.1(1490), 17.l(sh), 15.3 14.8(750) 14,8sh(500), 16.9 14.7sh 15.6(925), 15.7sh(700),

I2.5sh I2.2sh

15.9 15.9(560), 14.6(25) IO.5 IO.0 I2.34sh 12.3sh 15.0bsh

IO.0 I3+3(200)

1742

L. EL-SAYED,M. F. ISKANDERand A. EL-TOUKHY

distorted square pyramidal geometry(Ill). It is, however, difficult to distinguish between high spin five-coordinate nickel(ll) or cobalt(II) complexes of square pyramidal and trigonal bipyramidal symmetries particularly if distortion occurs[19].

rq\ /s--.~ Py

s/Ni\NJ

I NzM~,s Co--S~

(Ill) Furthermore, the solution spectra of bis nickel(II) complexes with the acetophenone derivative (iii) in pyridine are not much altered from the solid or solution spectra in benzene, indicating that no interaction has occurred. However, the spectrum of the corresponding Co(II) chelate (vii) in pyridine is similar to that of (v) in the same solvent (Fig. 2). Accordingly the five coordinate monopyridinate adduct is formed in solution, but no solid adduct could be isolated. With regard to the interaction of bis copper(II) chelates (ix), (x) and (xi) with pyridine, no definite conclusion can be reached from the study of their electronic spectra in pyridine. The formation of five-coordinate pyridme monoadducts only with bis N-isopropylidene- and N-cyclohexylidene-hydrazineS-methyldithiocarboxylatenickel (ll) and cobalt(II) chelates can be ascribed to steric factors in the ketone residue of these complexes. The axial coordination of one pyridine molecule may distort the coordination polyhedron so that attack of a second pyridine molecule is unfavourable. Since no X-ray structural analysis is available, it is very difficult to confirm the extent of such distortion in these 5-coordinate monoadducts. However, X-ray data on the quinoline monoadduct of bis (diethyldithio-phosphinato) nickel(II) have shown that the nickel atom lies 0.52A above the plane of the four sulphur atoms forming the base of the pyramid with the apex occupied by the quinoline nitrogen[22]. On the other hand square planar bis nickel(II) chelates with N-substituted benzylidene hydrazine S-methyl dithiocarboxylate were found to form sixcoordinate biadduct in pyridine solutions[3]. Attempts to isolate these-biadducts failed due to the rapid loss of pyridine. Only in the case of the o-nitrobenzaldehyde derivative, a stable yellow biadduct was isolated[3]. The phenyl groups in these chelates are most probably coplanar with the chelate rings forming a fully conjugated rigid planar structure with available p: nickel(II) orbitals. This permits the interaction of two pyridine molecules in the trans axial positions. In the corresponding Ni(II) complex with the acetophenone derivative (iii) it is suggested that the presence of the methyl groups makes the benzene rings tilted, thus offering

some crowding for any possible interaction to occur. The metal(II) chelates with acetone and cyclohexanone residues seem to be sterically intermediate between the benzaldehyde and acetophenone derivatives allowing the coordination of only one pyridine molecule. A survey in literature[20, 22-25] has revealed that stable five-coordinate monoadducts are usually formed with bulky Lewis bases such as quinoline[22-25] and ~-picoline[23-25]. In the present work, however, it seems that the formation of five-coordinate monoadducts is due to the steric requirements of the four coordinate Lewis acids. The thermodynamics of these adduct formation reactions are in progress. EXPERIMENTAL

Preparation of the ligands

Hydrazine-S-methyldithiocarboxylate was prepared using the method previously described[l]. The Schiff bases were obtained by refluxing for about ½ hr, an equimolecular amount of the methyl ester and the ketone (acetone, cyclohexanone and acetophenone) in methanol. The crude product was recrystallized from ethanol. Preparation of the bis metal(II) complexes A solution of the metal(II) acetate (0.01 mole) in ethanol (30 ml) was treated with a solution of the Schiff base (0.02 mole) in absolute ethanol (40 ml). The reacting mixture was refluxed for 10 rain and left to cool. The bis neutral metal(If) complexes precipitated out, were filtered and washed with ethanol. These complexes were recrystallized from chloroform-light petroleum mixture. The analytical data are given in Table 1. Preparation of bis(N-isopropylidene-hydrazine-S-methyl thiocarboxylate) Ni(II) and Co(II) monopyridinates

di-

The bis neutral metal(II) complex (2gm) was dissolved in pyridine (10 ml). The solution was heated on a water bath for 10 min then treated with 10 ml of dry benzene. On cooling the monopyridinate adduct precipitated out. It was filtered and washed with dry benzene. Physical measurements Magnetic and spectral data were obtained using the same procedures previously described[26]. Thermogravimetric and differential thermal analysis were performed on a Derivatograph Model D-102, manufactured by MOM (Hungary) using AI20 3 as standard. REFERENCES

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1743

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