Aralkylpolyamine complexes—VI

J. inorg, nucl. Chem., 1974, Vol. 36, pp. 565-568. Pergamon Press. Printed in Great Britain.

ARALKYLPOLYAMINE COMPLEXES--VI COMPLEXES

OF NICKEL(II) WITH N-BENZYLETHYLENEDIAMINE K. C. PATEL* and DAVID E. GOLDBERG

Department of Chemistry, Brooklyn College of the City University of New York, Brooklyn, New York 11210 (First received 1 February 1973; in revised form 30 April 1973)

Abstract--Eight new complexes are reported: Ni(MBEn)2X2 (X = C1, Br, I, or NO3); Ni(MBEn)2(I)NO3 ; Ni(MBEn)2(H20)2SO4; and blue and light-pink Ni(MBEn)a(CIO4)2. Their structures are deduced from reflectance spectra at room and liquid nitrogen temperatures and from i.r. spectra. Ni(MBEn)3(CIO4)2 has been isolated in two isomeric forms. The spectrochemical series for the ligands investigated with nickel(II) ion is deduced as H20 < MBEn < NH3 < En.

INTRODUCTION COM/'L~XES of nickel(II) perchlorate-['NiL2(H20)2 ] (CIO4)2-containing two molecules of water and two molecules of ethylenediamine (En) or N,N'-dibenzylethylenediamine (DBEn) are interesting in that two types of complexes can be isolated with each of the m i n e s . The two molecules of water can easily be removed from one complex of each to produce a planar complex. The other complex of each does not lose water molecules easily[I, 2]. Steric effects limit the coordination of the DBEn ligand and produce only mono and bis complexes in the solid state[3] even though stability constant studies in a water-dioxane system indicate the possibility of tris complexes also with both N-benzylethylenediamine(MBEn) and DBEn as ligands [4]. In addition, since the MBEn ligand is unsymmetric, isomeric forms of tris complexes might be expected. Hence the present investigation was undertaken. EXPERIMENTAL Nickel(II) salts and sodium iodide (all reagent grade) were used without further purification. N-benzylethylenediamine

was prepared as described previously[4]. Physical measurements were carried out as described earlier[5]. Analytical results are presented in Table 1. Ni(MBEn)2X2 (X = CI, Br or NO3) The above complexes were obtained by the addition of stoichiometric quantities of MBEn in ethanol to ethanolic solutions of the appropriate hydrated nickel(II) salts. The complexes separated on shaking and were washed with ethanol, and dried in a desiccator. Ni(MBEn)2I2 and Ni(MBEn)2(I)NO3 Ethanolic solutions containing one or two moles of iodide per mole of nickel(II) were prepared by treating an ethanolic solution of Ni(H20)6(NO3) 2 with stoichiometric quantities of solid NaI. Precipitated NaNO3 was removed by filtration. Solid complexes were then obtained by the treatment of the above solutions (0.02 mole) with ethanolic MBEn (0..04mole). Ni(MBEn)2(H20)2SO4 A bluish pink solid was obtained from an aqueous solution of NiSO4.6H20 (0.02 mole) when treated with MBEn (0.04 mole) in acetone.

Table 1. Analytical results*

Compound

C

Calculated H

N

C

Found H

N

Ni(MBEn)3(C104)2 (A) Ni(MBEn)a(C104) 2 (B) Ni(MBEn)2(NOa)2 Ni(MBEn)2SO4.2H20 Ni(MBEn)2CI2 Ni(MBEn)2Br2 Ni(MBEn)212 Ni(MBEn)2I. NO3

45.8 45'8 44.75 44.0 50"2 41.6 35"25 39.4

5.9 5'9 5'8 6'5 6'5 5-4 4.6 5.1

11.9 11'9 17.4 11'4 13.0 10"8 9-15 12.8

46.9 45.8 46.0 43.8 50-1 41.5 35.5 38-55

6.1 5'9 5'9 6'6 6"5 5-3 4"8 5.1

12.0 12.4 17'8 11-2 13"0 11'0 9.4 12.5

* Bernhardt Microanalytical Laboratory, West Germany. 565

566

K. C. PATELand DAVIDE. GOLDBERG

Ni(MBEn)3(CIO4)2 blue (A) and light pink (B) (A) Ni(H20)6(CIO4)2 (0-02 mole) was dissolved in 95 per cent ethanol (100 ml) and added to MBEn (0-06mole) at room temperature. After decantation the resulting gummy product was dissolved in acetone and the liquid was stirred continuously for 1.5 hr at 60"C. The blue solid crystallized and was filtered, washed with acetone, and dried. (B) An ice-cold ethanolie (95 per cent) solution of Ni(H20)6(C104)2 (0-02 mole) was treated very slowly with cold MBEn (0"04 mole). The resulting blue solution gave a light pink solid on stirring for about 3 hr. This preparation is nonreproducible. RESULTS AND DISCUSSION Room and liquid nitrogen temperature reflectance spectral data are given in Table 2. Ni(MBEn)2X 2 (X = CI, Br, I) complexes These complexes have a trans-octahedral structure, with the local symmetry of the coordination sphere of the metal ion approximating D4h. In this symmetry, the 3T2g and 3Tlg(F) levels of an octahedral complex split into 3B2g + 3Eg and 3A2g + 3Eg levels, respectively (Fig. 1). Hence four bands were expected in the region

3F

3rig

~

3r2g

( , - - ~a2i

3A2, q

382

3~'tg

~,4r - -

382

_ _

3A2

Free ion Oh field D4h C2v Fig. 1. Energy level diagram for d' ion in different fields.

7000-19000 crn-1. The two bands corresponding to transitions to 3E. levels were expected to be of higher intensity compar'ed to the other two bands. The usual order of levels, when the axial field is weak, is 3Big < 3Es < 3B2g < 3A2g < 3Es. However in these complexes, instead of four bands, only three bands were seen--a comparatively broad weak band due to the transition 3Big--* 3B2g, 3A2g between the strong bands due to the 3B15 ~ 3Eg(3Tlg(F)) and 3Big ~ 3Eg(aT2g) transitions. In the above complexes, since the halide ions are weaker ligands than MBEn, the oetahedral structure is expected to be elongated along the fourfold axis. In such cases the parameter Df is related to the difference in the octahedral lODq value for the two different ligands in the complexes by lODq(xy) - lODq(z) = (70/4)Dt, where~ lODq(xy) and lODq(z) refer to the values for in-plane and axial ligands, respectively. Dz and Ds values, calculated for Ni(MBEn)2t 2 from the room temperature reflectance spectra, are 390 and 619 era- ~, respectively. These values are quite comparable[6] with the values for NiPy4I 2

(/9, = 4 0 0

crn -x a n d

D, = 600 cm-:).

For [Ni(MBEn)2] 2+ complexes, the transition to the 3Eg(3T2g) state, which is predominantly a function of lODq for MBEn and D,, lies near 8000 era-~. A weak splitting of this band can be attributed to a small deviation from D,,h symmetry. Thus in C2v symmetry, the splitting of this band can be assigned to the 3A2 --* 3B1 and 3.42-~ 3B2 transitions, respectively (Fig. 1). The transition to the 3B2g state is dependent only on the in-plane field strength, lODq for MBEn, which is measured from the reflectance spectrum of Ni(MBEn)3(C104) 2 as 10,550 crn -1. However, it is expected that the Dq value for MBEn would probably be greater in the bis complex than in Ni(MBEn)a(C104) 2 because steric repulsions of MBEn ligands would be lower in the bis complex. Hence the band at 12,100 cm- x in the spectrum of Ni(MBEn)2Br 2 can be assigned to the 3Big --, 3B2g transition. A spin-forbidden transition is also expected in this region, which might be one reason for the broadness of this band. The band at

Table 2. Electronic spectral data (cm- ~ x 103) Diffuse reflectance spectra Compound Ni(MBEn)2C12 Ni(MBEn)2Br2 Ni(MBEn)212 Ni(MBEn)2(NOa)2 Ni(MBEn)2I. NO 3 Ni(MBEn)2(H20)2SO 4 Ni(MBEn)a(C104)2 (A) Ni(MBEn)a(CIO4)2 (B)

Temp(*K)

Va

295 80 295 80 295 80295 80 295 80 295 80 295 80 295 80

27.4 27.4 27"0 27.0 ~29"0 ~ 29-2 ~29.0 ~29"2 ~28.6 ~ 28.6 28.6 28"6 28'6 28'8

v2 17.25 17.55 17.10 17.40 17.90 18-0 18-2 18'2 17.9 17"9 17.6 17.6 17.7 17"7 18"0 18.2

v1 14.0 14.1 14-1sh 13"6 13.7 13.6 13"3vb 13'3vb 13.5vb 13-4vb 12.3 12'3 12.3sh 12'3sh 12'3sh 12.2

12.6vb 12.6vb 12"lb 12"1b 11-6b 12.0

8.0vb 8.3,8.0 8"4, 8"0 8"25,7"9 8.2b,~8.0 8.15 8"77vb 8"77vb 8.06vb 8'06vb 9-175vb 9"26vb 10.5b 10.75vb 10"6b 10"8b

B

v2/v 1 2"16 2'10

1390

2"08

1515

2.22

1245

1"92

987

1'69

987

1"70

567

Aralkylpolyaminecomplexes--V 14,100 cm-1 is weaker in intensity than the band at 17,100 cm-1, hence these two bands are attributed to tbe transitions SBII ~ SA2sand SBlz ~ 3Eg,respectively. The band at 27,000 can- ~ is very broad, and hence can be assigned to the SBI. "--,3A2g, 3Es(aTIs(P)) transitions. The reflectance s~x~tra of Ni(MBEn)2C12 and Ni(MBEn)212 are identical to the spectrum of Ni(MBEn)2Br2 except for the following, and hence the bands can be assigned similarly. (1) The splitting of the lowest energy band in the spectrum of the chloride is observed only at liquid nitrogen temperature. (2) Only one component of the lowest energy transition is observed in the spectrum of the iodide complex due to the limitation of the spectrophotometer used; however, the intensity increase suggests the possibility of a band closer to 8000 cm-1 (Fig. 2). The highest energy transition is masked due to charge transfer transitions.

sitions. The v~Jv, ratios (Table 2t based on the room temperature spectra, sugSest the dis'~ortion effect in these complexes and those in the halide complexes are of the same order of magnitude. Ni(MBEn)2(H20)2SO4 Comparison of t h e i.r. spectra of Ni(MBEn)2(H20)2SO4 and Ni(MBEn)2C12 in the 8-11 # region clearly indicates the presence of ionic sulfate in the former complex (Fig. 3). A single band

o3

O'1

, 3500

I

5500

I

7,500

I

9500

I

8

9

IO

I

I

11,500 13,500

Wavelength,

Fig. 2. Reflectance spectrum of Ni(MBEn)212 at room (a) and liquid nitrogen (b) temperatures. Ni(MBEn)2(NO3)2 and Ni(MBEn)2(I)NO3 The symmetry of the nitrate ion (D3h) lowers to C2v on coordination, and the degeneracy of the v4 and v3 vibrations is lifted. In the i.r. spectra of the above complexes the regions of the Vl and v4 vibrations are covered by the strong amine and the aromatic ring vibrations. Hence, the present study is limited to only the v2 and va vibrations. Both spectra show strong bands at 1420 and 1310 cm -1, and a sharp band of medium intensity at 820 era-1. The first two bands can be assigned to the components of v3 and the last one to v2 vibrations of a monodentate nitrate group[7]. The reflectance spectra of these complexes are identi• cal, each having only three bands between 8000 and 19,000 era-1. As discussed above for the halide complexes, these three bands can be assigned to the aBls-..,aEg(aT2g); aBlg--,3B2g, 3A2s; and 3B,g--,3Eg(3Tls(F)) transitions, respectively. The band near 29,000 cm-1 cart be assigned to the 3Big--, 3A2g, aEg(3Tlg(P)) tran-

Fig. 3. I.R. Spectra of(a) Ni(MBEn)2CI 2, and (b) [Ni(MBEn)2(H20)2]SO4. near 1600 cm-1 in the i.r. spectrum of all anhydrous MBEn complexes is split into two sharp bands at 1590 and 1610 cm-' in t h e spectrum of Ni(MBEn)2(H20)2SO4. The band at 1620 cm-1 can be assigned to the OH bending vibrations of the coordinated water and the 1590 cm -1 band can be Table 3. I.R. bands in the regions ofNH 2 and NH vibrations (cm- 1) (L = MBEn) Compound NiL2CI2 NiL2Br2 NiL212 NiL2I(NO3) NiL2(H20)2SO 4 NiL3(CIO,)2 (A) NiL3(C104)2 (B) NiL2(NOa)2

vNH2

vNH

6NH2

3300,3250 3280,3220 3225, 3200 3300, 3225 3300, 3225 (3350, 3450) 3300, 3225 3225,3250 3290,3225

3180 3130 3125 3160 3125

1600 1593 1590 1600 1590 (1610) 1590 1600 1620

3125 3200 3180

568

K. C. PATELand DAVIDE. GOLDBBRG

assigned to ~NH2 vibrations. The additional bands at 3350 and 3450 era-1, besides bands duo to NH 2 and NH vibrations in the 3000-3500 cra- 1 region, can then be assigned to OH symmetric and asymmetric stretching vibrations respectively of the coordinated water (Table 3). The reflectance spectrum of this complex has three main bands at 9175, 17,600, and ~28,600 cm -1 and a weak band at 12,300 crn- 1; a characteristic spectrum of hexacoordinated nickel(II) ion. Hence the complex ion must be [Ni(MBEn)2(H20)2] 2+, with bidentate MBEn ligands. Assignment of the above bands can be made similar to that of the Ni(MBEn)2(NO3)2 complex. Values of B for all the complexes except the halides are calculated from the diagonal sum rule[8] assuming Oh symmetry, and are reported in Table 2. These values are much greater than the free ion value of 1080 cm- 1, which suggests high distortion from Oh symmetry. The order of the distortion, CIO 4 < SO 4 < NO 3 < I. NOa, can be given from the B values. The v2/v 1 ratio also follows the same order.

has been suggested that c/s and trans octahedral nickel(II) complexes can be distinguished by the much greater splitting of the band system in the trans complex and also by the higher intensity of the absorption bands associated with the cis complex[10]. In the present case, the reflectance bands are non-split and of low intensity. Hence, neither cis nor trans structures are assignable according to the above statement. The assignment of the bands at 10,600, 18,000 and 28,600 cm- 1 to the transitions aA2g--, aT2s, 3A2g---*aTlg and 3A2~-, aTlg(P ), respectively, can be made. The shoulder at 12,300 cm -1 can be assigned to the spinforbidden transition aA2g--*1E~(1D), which is expected to lie at a higherenergy than the 3T2gterm in complexes where Dq is less than 1200 cm- 1. From the position of the v1band, the average Dq value calculated is 1055 cm- 1 which is significantly less than the Dq value of 1130 cm- 1 found for [NiEn3] (CIO4)2. This is in agreement with the prediction made from the stability constant measurements[4].

Ni(MBEn)a(CIO4)2, (A) and (B)

REFERENCES 1. M. E. Farago, J. M. James and V. C. G. Trcw, J. chem. Soc. (A), 820 (1967). 2. K. C. Pate1 and L. F. Larkworthy, Unpublished results. 3. K. C. Patel and L. F. Larkworthy, J. inorg, nud. Chem. 32, 1263 (1970). 4. D. E. Goldberg and K. C. Patel, J. inorg, nucl. Chem. 34, 3583 (1972). 5. K. C. Patel and D. E. Goldberg, Inorg. Chem. 11, 759 (1972). 6. D. A. Rowley and R. S. Drago, Inorg. Chem. 6, 1092 (1967). 7. N. F. Curtis and Y. M. Curtis, Inorg. Chem. 4, 804 (1965). 8. O. Bostoup and C. K. Jorgensen, Acta chem. scand. 11, 1223 (1957). 9. K. C. Patel and D. E. Goldberg, J. inorg, nucl. Chem. 34, 637 (1972). 10. C. J. Ballhausen, Introduction to Ligand Field Theory, p. 107. McGraw-Hill, New York (1962).

Each of the above complexes has a single, strong, broad i.r. band near 1100 era-1, and a weak band at 925 era- 1, characteristic of an ionic perchlorate group. The reflectance spectra at room and liquid nitrogen temperatures of both complexes are identical in all respects (Table 2). The v2/vl band ratio of 1.69 is comparable to those of [NiEn3](C104)2, [Ni(DBEn)20NCS)2] and [Ni(DBEn)2(NCSe)2][9], each of which also has six nitrogen donor atoms. Values of about 1.60 to 1.65 are common for nickel(II) complexes of Oh symmetry[9]. Hence the geometry of the above two complexes is almost octahedral. In the sequence of ligands En, MBEn, DBEn, the first and the third ligands generally form trans complexes. Exceptions to this generalization are [NiEn2C12] and [Ni(DBEn)z0NOa)]NOa. Hence, it is reasonable to expect trans complexes with the MBEn ligand also. It