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Complexes of Some Platinum Metals with /»-Diethylamino Anil of Phenyl Glyoxal H. S. Verma and R. C. Saxena Department of Chemistry, J. V. Post-Graduate College, Baraut-250611, India Z. Naturforsch. 33b, 1001-1004 (1978); received March 13/May 29, 1978 Bidentate Schiff Base Complexes, Magnetic Studies, Spectral Studies, Complex Compounds

Complex compounds of platinum metals Ru(III), Rh(III), Os(IV), Ir(IlI) and Pt(IV) with the bidentate Schiff base ligand derived by the condensation of phenyl glyoxal with p-diethylamino aniline have been prepared and characterized. All the complexes are stable at room temperature. The complexes of Ru(III) and Os(IV) are Paramagnetic and the other complexes of Rh(III), Ir(III) and Pt(IV) are diamagnetic. The spectral studies and the calculation of ligand field parameters clearly indicate the octahedral structure of these complexes.

Introduction

Schiff bases are known to possess tuberculostatic [1], fungicidal [2] and bacteriostatic [3] activities, on the other hand, have long been known for their capability of acting as potential chelating reagents. We have synthesised the Schiff base under study i.e. diethylamino anil of phenyl glyoxal (henceforth abbreviated as DEAPG):

and investigated its chelating behaviour by complex formation with platinum metal ions. The present communication reports the isolation of bis-com-plexes of the type [M(DEAPG)2C12]C1, where M = Ru(III), Rh(III), Ir(III), and [M(DEAPG)2C12]C12, where M = Os(IV) and Pt(IV), and their characteri-zation through elemental analyses, magnetic sus-ceptibility measurements at room temperature, molar conductance values, infrared and electronic spectra in solution.

Experimental

Materials: Hydrated IrCl3, RhCl3, RUC13, OsCl4 were obtained from Fluka, Switzerland and chloro-platinic acid from Johnson Matthey Chemicals, London. The ligand was prepared as described in literature [4]. All the other chemicals used were of reagent grade.

Requests for reprints should be sent to Dr. H. S. Verma, Chemical Laboratories, J. V. Post-Graduate College, Baraut - 250611, India.

Preparation and isolation of complexes A general procedure was adopted to synthesise

the complexes by mixing Ru(III), Rh(III), Ir(III), Os(IV) and Pt(IV) chloride (lOmmole each) in 25 ml acetone with 20 mmole of DEAPG separately. The reaction mixture was concentrated in a vacuum desiccator yi elding the coloured crystalline materials. The crystals were washed with ether and dried.

Elemental analysis and physical measurements The analyses of carbon, hydrogen and nitrogen

were done at the micro analytical section, C. D. R. I., Lucknow (India). Rhodium, iridum and ruthenium contents were estimated by the usual hydrolytic precipitation method, platinum content was deter-mined gravimetrically by precipitating with thio-salicylamide [5]. The chloride estimation was carried out by Volhard's method. The physical measurements viz. magnetic susceptibility (on a Gouy's balance), infrared spectra (on Perkin-Elmer infrared spectrophotometer model - 521 fitted with NaCl and KBr optices), absorption spectra (using UNICAM SP-500 spectrophotometer) and molar conductance (using Phillips conductivity bridge type LBR/B) have been recorded at room tem-perature.

Results and Discussion The complexes investigated in this work are

presented in Table I, along with their colour, analytical data and other properties (e.g. magnetic susceptibility and molar conductance). All the complexes are fairly stable at room temperature and can be stored without any change for a long time. The results of magnetic measurements in Table I show the diamagnetic nature of Rh(III), Ir(III) and Pt(IV) complexes and paramagnetic nature of Ru(III) and Os(IV) complexes. From these data one should expect an octahedral type of arrangement of the ligand around the metal ion,

1002 H. C. Verma-R. S. Saxena • Complexes of Some Platinum Metals

Table I. Analytical data, formulae and other properties of the complexes.

Complex Colour Analysis* [ % ] [ % ]

Metal Nitrogen [%]** Chlorine

A<eff. in B. M. (297 K)

Molar conductance Am (ohm-1 • cm2 • mole-1) in 1 x IO-3 M solution in D. M. F.

1. [RU(DEAPG)2C12]C1 Violet 12.96(13.16) 2.14(2.29) 13.75(13.87) 1.45 118.60 2. [Rh(DEAPG)2Cl2]Cl Pink 13.11(13.37) 2.18(2.27) 13.78(13.37) 0.30 119.64 3. [OS(DEAPG)2C12]C12 Pale-

Yellow 4.31(4.57) 23.02(23.19) 1.30 164.00

4. [Ir(DEAPG)2Cl2]Cl Pink 22.12(22.38) 6.38(6.52) 12.18(12.40) 0.40 121.40 5. [Pt(DEAPG)2Cl2]Cl2 Yellow 24.49(24.78) 6.82(7.11) 17.92(18.04) 0.84 166.20

* Theoretical values in brackets, ** including the ionic chlorine DEAPG: p-diethylamino anil of phenyl glyoxal, *** osmium could not be estimated due to the non-availability of a suitable method.

thus forming d2sp3 type of bonding. The molar conductance of the complexes of Ru(III), Rh(III) and Ir(III) in DMF (Table I) reveals their uni-univalent nature, but the complexes with Os(IV) and Pt(IV) are uni-bivalent electrolytes.

Electronic spectral studies

[Ru(DEAPG)2Cl2]Cl complex: The ground state of Ru(III) ion is 2T2g and the first excited doublet level will be 2A2g(t2g)4(eg)1 and 2Tig(t2g)4(eg)i. Its spectra are known for the chloride complex [ R U ( H 2 0 ) C 1 5 ] - 2 [ 6 ] , but the excited state is not definitely known except that it is spin-allowed. In octahedral ligand field symmetry the spectrum of ruthenium (III) should show the spin-allowed d -d bands in the visible region [7], corresponding to the transition: 2T2 g ->2A2 g , 2T2g and 2 T i g ^ 2 E g .

The electronic spectra of the complex under study consist of five absorption bands at 15340 cm - 1 , 19000 cm-1, 20570 cm-1, 31515 cm-1 and 34800 cm"1. Tanabe and Sugano matrices [8] predict the eight transitions from the ground state (t2g)5 to the doublet states of the configuration (t2g)4 (eg)1 and two transitions from the ground state to the quartet states of (t2g)4(eg)1. The band at 19000 cm - 1 may be due to 2T2g 2A2g transition and the two bands 15340 cm - 1 and 20570 cm - 1 are assigned to the two spin-forbidden transitions.

[Rh(DEAPG)2Cl2]Cl complex: The ground state for the Rh(III) ion in the complex is 1Aig(t2g)6 and the singlet excited states are !Txg and xT2g belonging to the configuration (t2g)5(eg)1. For this complex four bands have been observed at 14380 cm - 1 , 26300 cm-1, 37500 cm-1 and 45000 cm"1 ; the bands

at 26300 and 37500 cm-1 are probably due to electronic transitions 1 Aig xTig and 1 Aig 1T2g, respectively; the band appearing at 14380 cm - 1 may be spin-forbidden involving singlet-triplet transition iAig 3Tig and the fourth band (45000 cm-1) is a charge transfer one which is generally obtained in Rh(III) complexes. Using Ballhausen's energy equation [9] the ligand field splitting energy (10 Dq) comes out to be 22260 cm - 1 and the corresponding L. F. S. E. is 25.44 kcal/mole.

[Os(DEAPG)2Ch]Ch complex: The spectrum of the complex shows four bands appearing at 17750 cm-1, 20000 cm-1, 36170 cm-1 and 40540 cm-1. According to Ballhausen the ground state for Os(IV) would be (J»S)4 producing a Ti level. The band at 17750 cm - 1 can be assigned to the transition Ti -> Ti while at 20000 cm - 1 to Ti -> T2 and the other two bands may be considered to have arisen due to charge transfer.

[Ir(DEAPG)2Cl2]Cl complex: The ground state of Ir(III) is similar to Rh(III). The electronic spectra of the present complex consists of three bands at 18000 cm-1, 25000 cm-1 and 32640 cm-1 which may be assigned to 1 Aig - » 3Tig ,1 A i g -> !Tig and1 A i g ^ g , respectively. The splitting energy (10 Dq ) and L.F.S.E. obtained by Ballhausen equation cor-respond to the values at 28500 cm - 1 and 32.57 kcal/ mole, respectively. However, the factor KB2 /10 D q

has been ignored because of higher value of 10 Dq

and low value of B (478 cm - 1 ) observed in the complex (Table II).

[Pt(DEAPG)2Cl2]Cl2 complex: Three d-d-transi-tions have been observed in the spectra of Pt(IV) complex, two of these are spin allowed involving

1003 H. C. Verma-R. S. Saxena • Complexes of Some Platinum Metals

Table II. Electronic spectral studies and relevant ligand field parameters.

Complex Position of band [cm -1]

Assignments 10 Dq [cm -1]

B [cm -1]

ß L. F. S. E. kcal/mole

1. [RU(DEAPG)2C12]C1 15340 19000 20570 31515 34800

2T2g -> 2A2g 33350 654

2. [Rh(DEAPG)2Cl2]Cl 14380 26300 37500 45000

1A* -> 3Tig ->lrTig -^Tsg

charge transfer

22260 700 0.97 25.44

3. [OS(DEAPG)2C12]C12 17750 20000 36170 40540 charge transfer

4. [Ir(DEAPG)2Cl2]Cl 18000 25000 32640

iA lg 3T lg -> !T l g -> l rr2g

28500 478 0.72 32.57

5. [Pt(DEAPG)2Cl2]Cl2 20000 26300 36560 38631 40360

xAig 3Tig ->iT l g -> l rr2g

a, iTiu b, xTiu

29450 660 0.91 33.65

transitions lAig-^Tig (26300 cm-»), (36560 cm - 1 ) and one spin-forbidden xAig 3Tig

(20000 cm - 1). Besides these, two charge-transfer bands at 38631 cm - 1 and 40360 cm - 1 have also been observed. The values of 10 Dq , L.F.S.E. , Racah's parameters B and C have been evaluated as 29450 cm - 1 , 33.65 kcal/mole, 660 cm - 1 and 3150 cm - 1 , respectively (Table II).

Infrared spectral studies: Infrared spectral data for the DEAPG and its complexes indicate that most of the frequencies are perturbed on complex formation. Strong peaks corresponding to > C = 0 and - C H = N - g r o u p s (1710 cm - 1 and 1640 cm - 1) are shifted to lower values ranging from 1650 cm - 1 to 1696 cm - 1 and 1600 cm - 1 to 1635 cm - 1 , respectively, during complexation indicating that these two groups are participating in chelation. Appearance of new bands in the range 500 cm - 1 to 655 cm - 1 and 340 cm - 1 to 585 cm - 1 which are attributed [10-13] to metal-nitrogen and metal-oxygen link, respec-tively, further confirms the sites of chelation. Bands

in the range 320 cm - 1 to 550 cm - 1 suggest metal-chlorine links [14] as a result of complexation.

Position in spectro-chemical and nephelauxetic series: The different values of splitting energy (10 Dq) in case of octahedral complexes suggest that the position of the ligand (DEAPG) in the spectro-chemical series is somewhere between oxalate and water: I - < B r - < NCN - < F - < Urea < O H - < CH3COO- < Ox - 2 < DEAPG < HaO < SCN- < glycine ~ enta < Py ~ NH3 < en ~ Tren < SO3 < dipy < O-phen < N02~ < CN - . The corresponding series for the metal ions:

Rh3 + < Ir3+ < Pt4+ < Ru3 + .

The position of the ligand in nephelauxetic series is somewhere between water and urea:

F - > H 2 0 ~ DEAPG > Urea > NH3 > en > Ox - 2 > SCN - > Cl - ~ C N - > B r - > I - .

The corresponding series of metal ions:

Rh3 + > Pt4+ > Ir3+.

[1] P. Job, Liebigs Ann. 9, 113 (1928); 16, 97 (1936).

[2] J. H. Yoe and A. L. Lones, Industrial Eng. Anal. Ed. 16, 11 (1944).

[3] A. E. Harvey and D. L. Mannings, J. Am. Chem. Soc. 72, 4448 (1950).

[4] R. C. Saxena, C. L. Jain, J. N. Rastogi, and S. C. Rastogi, J. Chem. Eng. Data 6, 29 (1975).

[5] K. Sur and S. C. Shome, Anal. Chim. Acta 57, 201 (1971).

[6] P. Wehner and J. C. Hindman, J. Phys. Chem. 56, 10 (1952).

1004 H. C. Verma-R. S. Saxena • Complexes of Some Platinum Metals

[7] C. K . J0rgensen, Acta Chem. Scand. 10, 518 (1956).

[8] Y . Tanabe and S. Sugano, J. Phys. Soc. Jpn. 9, 753 (1954).

[9] R. Dingle and C. J. Ballhausen, Mat. Fis. Medd. Den. Vid. Selsk 35, 12 (1967).

[10] R . A. Condrate and K. Nakamoto, J. Chem. Phys. 42, 2590 (1965).

[11] G. W. Watt and J. F. Knifton, Inorg. Chem. 6, 1010 (1967).

[12] R . J. H. Clark and C. S. Williams, Inorg. Chem. 4, 350 (1965).

[13] J. R, During, W. A. Mc Allister, and E. E. Mercar, J. Inorg. Nucl. Chem. 29, 1441 (1967).

[14] D. P. Mellor and L. Maley, Nature (London) 159, 370 (1948).