N-aralkylpolyamine complexes—V

J. morg. nucl. Chem., 1973,Vol. 35, pp. 4041-4046. PergamonPress. Printedin Great Britain.

N-ARALKYLPOLYAMINE

COMPLEXES--V

COMPLEXES OF COPPER(II) WITH N-BENZYLETHYLENEDIAMINE K. C. PATEL* and DAVID E. GOLDBERG Contribution from the Department of Chemistry, Brooklyn College of the City University of New York, Brooklyn, N.Y. 11210 (Received 19 February 1973)

Abstract--The following N-benzylethylenediamine (MBEn) complexes were prepared: Cu(MBEn)2X / (X = CI, Br, I, NOa and C104), Cu(MBEn)2SO4. xH20 (x = 2 and 3) and Cu(MBEn)X2 (X = CI and Br). Their structures were deduced from their magnetic susceptibilities, reflectance spectra and i.r. spectra. MBEn and ethylenediamine (En) complexes have similar spectral behavior and therefore equivalent structures. The complexes with one MBEn molecule per copper ion have polymeric octahedral structures.

INTRODUCTION

BESIDES our own investigations[l] the only available report regarding the study of MBEn is its acid dissociation constants and the stability constants of the corresponding copper(II) chelates[2]. From our earlier investigations[3, 4], we found the need of systematic investigations of N-aralkylpolyamine ligands and their complexes with transition metal ions. At present we are working on ligands

R,\ //N-CH2-CH2-N~ R3

(R. = H -

or C6HsCH2- )

R4

with first transition series divalent metal ions. Here we report the preparations and properties of the mono and bis complexes of copper(II) with MBEn. All the complexes are new. Descriptions of corresponding complexes of En are also included for comparison. All attempts to make 1:3 complexes failed. EXPERIMENTAL Reagent grade copper(II) salts and sodium iodide were used, MBEn was prepared as described previously[2]. Spectrograde solvents were used for solution spectra and for molar conductance measurements. Analytical data are presented in Table 1. Physical measurements were carried out as described earlier[4]. (I) Dichloro-bis(N-benzylethylenediamine)copper(II):Ethanolic solutions of CuC12 (0"01 mole) and MBEn (0.02 mole) were mixed, The violet solid which soon separated was filtered, washed with ethanol and dried in a vacuum desiccator over CaCI2. Bis(N-benzylethylenediamine)copper(II)perchlorate and 1. 2. 3. 4.

K. C. Patel and D. E. Goldberg, J. inorg, nucl. Chem. 34, 637 (1972); ibid. 34, 3583 (1972). A. E. Frost and A. A. Carison, J. org. Chem. 24, 1581 (1959). L. F. Larkworthy and K. C. Patel, J. inorg, nucl. Chem. 32, 1263 (1970). K. C. Patel and D. E. Goldberg, Inorg. Chem. 11, 759 (1972). 4041

4042

K. C. PATEL and DAVID E. GOLDBERG Table 1. Analytical data*

Compound

C

Calcd H

N

C

Cu(MBEn):CI 2 Cu(MBEn)2Br 2 Cu(MBEn)212 Cu(MBEn)2(NO3) 2 Cu(MBEn)2(C104) 2 Cu(MBEn)2SO4(H20)2 Cu(MBEn)2SO4(H20)3 Cu(MBEn)Cl 2 Cu(MBEn)Br 2

49.8 41.3 35"0 44-35 38.4 43.6 42"0 38'0 28.95

6.45 5.35 4-5 5.75 5.0 6.5 6.6 4-95 3.75

12.9 10.7 9.1 17.2 9'9 11.3 10.9 9.9 --

49'1 40.1 35-5 44.25 38"2 44-4 41.45 37'8 29"9

Found H 6'8 5'4 4-85 5.8 5-0 6"7 6'4 5.1 3.7

N 13.1 10,8 10.9 17.2 9.9 10-7 10-6 9.7 --

* Bernhardt Microanalytical Laboratories, West Germany. dibromo-bis(N-benzylethylenediamine)copper(II) were prepared using the above method and appropriate copper(lI) salts with MBEn. (II) Diiodo-bis(N-benzylethylenediamine)copper(II): Cu(MBEn)2(NO3)2 was prepared by the quantitative treatment of Cu(NO3)2 • 3H20 and MBEn in ethanol. A suspension of mauve crystals of Cu(MBEn)2 (NO3)2 (0.01 mole) in ethanol when treated with an ethanolic solution of NaI (0.02 mole) gave a dirty blue solid which was filtered, washed with water first to remove NAN03, washed finally with ethanol and then dried. (III) Bis(N-benzylethylenediamine)copper(II) sulfate dihydrate: An aqueous solution of CuSO4. 5H20 (0'01 mole) was treated slowly with MBEn (0-02 mole) in methanol. The resulting blue solid was filtered, washed with methanol containing ligand and dried. Washing with methanol alone causes partial loss of the ligand. Cu(En)3SO4 was found[5] to lose a molecule of En on washing with ethanol. From the filtrate and washings, dark blue solid Cu(MBEn)2SO4.3H~O crystallized on standing. (IV) Dichloro-N-benzylethylenediaminecopper(II) and dibromo-N-benzylethylenediaminecopper (II): These complexes were prepared by treating ethanolic solutions of appropriate anhydrous copper(lI) salts (0.0t mole) with MBEn (0.01 mole). RESULTS AND DISCUSSION

Magnetic susceptibilities Magnetic susceptibilities of all the bis complexes, measured at 295° K, are reported in Table 2. All are magnetically normal, high-spin, octahedral copper(II) complexes. Table 2. Magnetic properties at 295°K

Cu(MBEn)2CI 2 Cu(MBEn)2Br 2 Cu(MBEn)2I 2 Cu(MBEn)2(NO3) 2 Cn(MBEn)2(C104)2 Cu(MBEn)2SO4(H~O)2 Cu(MBEn)2SO,~(H20)a Cu(MBEn)C12 Cu(MBEn) Br 2

Zcu × 106

/.t (B.M.)

Diamagnetic correction ( × 10 -~)

1531 1493 1337 1500 1538 1658 1675 1430 1353

1-91 1.89 1.79 1.89 1.91 1.99 2.00 1.84 1.80

263 285 317 254 280 282 295 155 177

5. G. Gordon and R. K. Birdwhistell, J. Am. chem. Soc. 81, 3567 (1959).

N-aralkylpolyamine complexes--VI

4043

Both the mono complexes show moments lower than the bis complexes. However the decrease is low, which might be an indication of weak antiferromagnetic interaction in a polymeric octahedral structure.

Electronic spectra Reflectance spectra of all the copper(II)-MBEn complexes are recorded in Table 3, along with the data for corresponding copper(II)-En complexes. A broad band between 16,000 and 19,000 cm- 1 appears in the reflectance spectra of all the bis complexes. In addition to this band, a weak shoulder has developed near 14,000 cm-~ in the halide complexes, while in the other complexes, the main band seems to be only asymmetric on the low energy side (Fig. 1). The 2D term of the free copper(II) ion (3d 9) in a weak octahedral field splits into an upper 2T2g level and a l o w e r 2Eg level, and only one spin-allowed transition results. However the crystal field theory predicts large distortions from cubic symmetry for the octahedral complexes of copper(II). Hence t h e 2Eg ground state cannot remain degenerate--it is Jahn Teller unstable--and this leads to a further splitting of the T2g and E~ levels, so that even in a complex with six identical donor atoms, a regular octahedral configuration is not expected. Ethylenediamine complexes of copper(II) have been studied from all angles[6~ and two extreme structures are recognized: (1) a square planar complex (extreme distortion) with an in-plane CuN 4 skeleton, and (2) a tetragonally distorted octahedral complex with in-plane CuN 4 skeleton and axially coordinated anions. The electronic Table 3. Reflectance spectra

Compound Cu(MBEn)2CI2 Cu(En)2CI 2 Cu(MBEn)EBr2 Cu(En)2Br2 Cu(MBEn)2I 2 Cu(En)212 Cu(MBEn)2(NOa) 2 Cu(En)z(NO3) 2 Cu(MBEn)2(CIO4) 2 Cu(En)2(C104)z Cu(MBEn)2SO 4 . 2HzO Cu(En)2SO 4 Cu(MBEn)zSO4(H20) 3 Cu(MBEn)C12 Cu(En)CI2 Cu(MBEn)Br 2 Cu(En)Br 2

Room temp. 17.4b, ~ 18.5, ~ 17.4b, 18.42, ~ 17-8b, ~ 18.08, ~ 18-8b* 18.9vb 18.5b* 19.00 16.7, 17.2, 17"5vb~" 13.5vb 15"3 14.8 sh, 15-2

(%.x x I0 -~) Liquid nitrogen temp.

12.9 sh 13.0 sh 13.5sh 13.0 sh 13.7 sh 13.0 sh

17.5, 13.1 sh 17.5, 13'8 sh 18.0, 13.8 sh 18'85b* 18-7b*

12.1 sh 13.0 sh

16.7, 12.5 sh 17"7~" 13"15, 15"0 sh

13.4

14"8 sh, 13.4

* Slight asymmetry on the low energy side of the band. t Large asymmetry on the low energy side of the band. 6. A. B. P. Lever and E. Mantovani,

Inorg. Chem, 10, 817 (1971);

and references therein.

4044

K . C . PATEL and DAVID E. G O L D B E R G 0.8 --

~t~ E

/

o.,-

'\

'

i ,,,,o 't f/"

i

0"5 ~

(1-4

"~

0"3

o.i 3200

,'~, 4200

5200

6200

7200

Wavelength,

8200

.....~ 9200

10200

J

Fig. 1. Reflectance spectra of: (A), Cu(MBEn)2CI 2 ; (B), Cu(MBEn)2Br2 ; (C), Cu(MBEn)2I 2 ; (D), Cu(MBEn)2(NO3)2 ; and (E), Cu(MBEn)2(CIO4)2. (Compounds are at room temperature.)

spectra of these complexes generally contain a broad band between 14,000 and 22,000 cm- 1 depending upon the nature of the in-plane amine and the axial ligand. For a tetragonal complex with weakly coordinated axial ligands, the maximum of the above band lies near the high energy end. This is the useful indication of the degree of tetragonal distortion. Hence the observed asymmetric electronic band near 18,500 cm -1 in the spectra of Cu(MBEn)2(NO3) 2 and Cu(MBEn)2(C104) 2 suggests strong distortion from octahedral stereochemistry. This is comparable with the results of corresponding En complexes (Table 3). Cu(En)2(NO3) 2 was studied by X-ray crystal structure analysis[7], which showed that one oxygen atom of each of two NO 3 groups is coordinated to the copper atom at a distance of 2.59/~, while the C u - N distance is only 2.03 ,~. The weak coordination of nitrate in Cu(MBEn)2(NO3) 2 has been confirmed by i.r. analysis (see i.r. section and Fig. 2). We have also noticed previously[3] that the band intensity increase parallels the increase in tetragonal distortion. The high intensity of the main reflectance band of Cu(MBEn)E(NO3) 2 and Cu(MBEn)2(C104) 2, compared to that of the halide complexes (Fig. 1), reflects the higher tetragonal distortion in the former two complexes. The reflectance spectra of the halide complexes are characterized by a broad, strong band near 17,500 cm- ~ and a well defined shoulder near 13,000 cm-1. The shoulder and the main band can be assigned t o 2Big --~ 2Alg a n d 2Big --', 2Eg, 2B2g transitions respectively in D4h symmetry. The shoulder has moved considerably (C1 < Br < I) to higher frequency (Table 3 and Fig. 1). The change of spectrum with anion shows that the anions are coordinated in the solids. The positions of the shoulder, with the order of energies C1 < Br < I, show that the degree of tetragonality 7. Y. Komiyama and E. C. Lingafelter,

Acta Crystallogr. 17,

1145 (1964).

N-aralkylpolyamine complexes--VI 1500

L'I1 ',

4045

1200

','J

A - Ni {MBEn)z(N03) 2 B = Cu ( M B E n ) 2 (NO3) 2

Fig. 2. Infrared spectra.

decreases in this order. The same order was observed[8] and assigned to the degree of tetragonality in Cr(En)2X2 (X = C1, Br, I). Just as in En complexes, the effect of distortion on the position of the main band is very small; hence the anions must be trans-coordinated in MBEn complexes also. The shoulder becomes more pronounced, the entire spectrum reduces in intensity, and the main band moves 100-200 cmhigher in frequency on cooling each compound to liquid nitrogen temperature. The reflectance spectrum of [Cu(MBEn)2SO4]. 2H20 is also characteristic of a tetragonal copper(II) complex; exhibiting a strong band at 16,700cm -1 and a shoulder at 12,100cm -1. However, the spectrum of Cu(MBEn)2SO4.3HzO has only one very broad band near 17,500 cm -1 with considerable asymmetry on the lower frequency side. This suggests higher distortion in the latter complex. The more intense color of this complex compared to the former one also supports this conclusion. In general, bis-complexes of MBEn are more comparable to the corresponding complexes[3, 4] of En than of DBEn, indicating that the steric effect is less important in the complexes of MBEn, a conclusion also reached from the stability constant studies[l]. The room temperature reflectance spectrum of Cu(MBEn)C12 has a very broad band at 13,500 cm- 1, which on cooling to liquid nitrogen temperature resolves into a band at 13,150 cm- 1 and a shoulder at 15,000 cm- 1. The spectrum of Cu(MBEn) Br 2 shows a broad band at 13,400 cm -1 and a shoulder at 14,800 cm-1, both at room and at liquid nitrogen temperatures. This behavior was also observed with Cu(DBEn)C12 and Cu(DBEn)Br2[3], hence, assignment of bands similar to that for the DBEn complexes is suggested for the MBEn complexes. 8. A. Earnshaw, L. F. Larkworthy and K. C. Patel, d. chem. Soc. (A), 1339 (1969).

4046

K . C . PATEL and DAVID E. GOLDBERG

Infrared spectra In Fig. 2 are presented the i.r. spectra ofNi(MBEn)2(NO3) 2 and Cu(MBEn)2(NO3) 2 between 1200 and 1500 cm- 1--the region of v3 vibration of the nitrate ion. The small splitting of this band suggests monodentate coordination of the nitrate ion in both complexes[9]. The magnitude of the splitting of this band was used as a measure of the covalent bonding of the nitrate group in the complexes of nickel(II), copper(II), cobalt(II) and zinc(II) containing bidentate nitrate groups, and the sequence of magnitudes of splitting Ni > Cu > Co > Zn was given[10]. The copper and nickel MBEn complexes, in which nitrate is monodentate, also follow the sequence Ni > Cu. However, the amount of splitting in the copper complex (65 cm-1) is very small compared to that in the nickel complex (110 cm-1), which definitely suggests much weaker coordination of the nitrate group in the copper complex. I.R. analysis of the perchlorate ion vibrational frequencies indicates unsplit, strong, broad, antisymmetric stretch absorption near 1070 cm- 1 in Cu(MBEn)2(C104)2. Hence it appears that perchlorate is not coordinated in this complex. A trans-octahedral structure with bridging sulphate groups has been assigned to Cu(En)2SO4[ll ]. Since in the 1100 cm -x region the i.r. bands of Cu(MBEn)2SO4. 2 H 2 0 and Cu(En)2SO4 are identical, a structure similar to Cu(En)2SO4 can also be deduced for Cu(MBEn)2SO4.2H20. 9. N. F. Curtis and Y. M. Curtis, Inorg. Chem. 4, 804 (1965). 10. E. J. Duff, M. N. Hughes and K. J. Rutt, J. chem. Soc. (A), 2126 (1969). 11. A. Earnshaw, L. F. Larkworthy and K. C. Patel, J. chem. Soc. (A), 1334 (1969).