The Nickel(11)-r-Picolin~Perchlorate Complex System

M. S. SUN AND D. G. BREWER Department of Chemistry, University of New Brunswick, Fredericton, New Brunswick

Received November 9, 1970

Three compounds have been isolated; uiz., NiL4(C104)2, NiL4(H20)2(C104)2, and NiL6(H20)2(C104)2 (L = y-picoline), and their spectral, magnetic, and other properties compared. Some tentative suggestions. as to the possible structure of the last complex are offered; the first two compounds were reported previously (1).

On a is016 trois composks: NiL4(C104)2, NiL4(H20)2(C104)2 et NiLb(H20)2(C104)2 (L = y-picoline); on compare leurs propriktks spectrales, magnktiques et autres. Alors que des deux premiers complexes ont fait I'objet d'une communication anterieure (I), on fait maintenant des suggestions plausibles concernant la structure du dernier complexe.

Canadian Journal of Chemistry, 49, 1502 (1971)

Introduction version of the blue NiL6(H20)2(C104)2 to the

In the course of an investigation into the nuclear yellow NiL4(C104), upon drying have led to a

magnetic resonance (n.m.r.) isotropic shifts of more detailed investigation of the spectral and

some nickel(I1) complexes with substituted pyri- physical properties of these compounds.

dines, it was'found necessary to become invoived Experimental with the Ni(ll)-~-~icoline-~erchlorate system'

NiL4(C104)2 and NiL4(H,0)2(C]04)2 were prepared in the literature were used according to previously published procedures (1). Better obtain two compounds, viz., NiL4(C104)2 and crystals of the former compound were obtained from a NiL4(H20)2(C104)2, but under other conditions, solution of y-picoline and nickel(I1) perchlorate hexa-

a third compound was obtained, viz., NiL,- hydrate (molar ratio 4:l) in hot butanol. NiLb(H20)2(C104)2 was precipitated as blue crystals

(H20)2(C104)2. The the upon the addition of an aqueous solution of Ni(C104)2. yellow NiL4(C104)2 to the blue NiL,(HzO)2- 6H,O to an aaueous solution of excess liaand. These (ClO,), when exposed to moisture, and the con- crystals were filiered off and air dried for several hours.

TABLE 1. Properties

Description

Parameter NiL4(C104)2 NiL4(H20)2(C104)2 NiLdH20)2(C104)2

Color

~ e t r @-M.)ll Thermal stability

Yellow

Diamagnetic

Blue

3.12 Loses water at 76 "C

Blue

3.11 Loses water and 2L at 73 "C

Melts and decomp. 222-252 "C

Molar conductancefi (mho cm2 mol-l) 0.01 M in CH2C12 at 23 "C Reaction with H 2 0 Blue ppte.5

green soh. Blue ppte.5 green soh.

No reaction (very slightly soluble)

Reaction with CH2C12 or CHC13 Green soln.

No reaction Blue-green soln. Blue soh.

Reaction with anhydrous ether

Turns yellow (loss of water)

Turns yellow (loss of water and ligand)

'Solution in y-picoline. ?After heating and cooling in y-picoline. $Solution in CHICll sat. with HnO: The blue ppte. was found to be N I L ~ ( H ~ O ) ~ ( C ~ O ~ ) ~ . W M agnetic measurements were madeon a Guoy type balance supplied by Newport Instruments (U.K.1 and through

the courtesy of Dr. F. Bottomley of this department. TlConductance measurements were made on an Industrial Instruments Model R C 16B2 Conductivity bridge. The

cell was calibrated with a standard aqueous solution of KCI. The conductivity of the solvent methylene chloride or y-picoline was found to be negligible.

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SUN AND BREWER: NICKEL-y-PICOLINE PERCHLORATE COMPLEX 1503

TABLE 2. Infrared spectra*

Frequency (cm-') in medium

Compound KBr Nujol CHC13 or CHzCIz Assignment

asym str. v3 asym. str. vl bend vz

C104 ~3

CIO4 Vl C104 V 4 Ni-N str.

H z 0 v3 H z 0 vl H z 0 vz v8a v60 v16b c104 v3 C104 V l c10, v4 Ni-N str.

?

N ~ L ~ ( H z ~ ) z ( C ~ ~ ~ ) Z 3450(m) 3420(m) 3420(~) H z 0 v3 3280(sh) H z 0 VI 1660(sh) 1682(m) 1670(sh) H z 0 vz 1616(s) 161 9(s), 1607(sh) 1622(s), 1607(sh) v8.

1141(vs), 1108(sh) 11 10-1055(br.vs) 1130(vs) 1 0 9 1 ( ~ ~ ) 1 0 3 0 ( ~ ~ ) C104 VJ 937(w) 925(w) 928(m) C104 vl 627(s) 62 1 (s) 620(s) c l o 4 v4 5 4 0 ( ~ ) 540(~) , 5 2 0 ( ~ ) 544(~) , 515(~h) v.50 495(~) 495(~), 486(~h) 492(~), 482(sh) V16b

270(w), 277(sh) Ni-N str. 228(m), 237(sh) ?

's = strong, m = medium, w = weak, v = very, sh = shoulder, br = broad. Infrared spectra were taken on a Beckman IR-12 spectrophotometer. Both KBr and Nujol mulls were used for the solid compounds in the 4000-200 cm-1 region. Solutions of the compounds in both chloroform and methylene chloride were also run using caesium bromide cells and polyethylene bags.

Anal. Calcd.: C, 50.70; H, 5.44; 0 , 18.76; N, 9.86; C1, 8.32; Ni, 6.89. Found: C, 49.88; H, 5.44; 0 , 19.58; N, 9.92; C1, 8.47; Ni, 6.67.

Analyses were performed by Dr. F. Pascher, Mikro- analytische Laboratorium, Bonn, West Germany.

Results and Discussion It is apparent that y-picoline, water, and

perchlorate compete in solution for the nickel(I1). It would also appear that some of these are not very strongly bound to the central metal, and ready conversion from one compound to another is observed.

In view of the previously assigned structures

for Ni(I1) complexes (1, 4) a square planar arrangement of four y-picoline molecules is assumed for all three compounds. The two blue compounds could then have water and y-pico- line, respectively, occupying the octahedral positions. I t is possible that the latter compound could be formulated as NiL4(H20)2(C104)2.2L, analogous to the compounds such as Ni(pyr),- (NC0),.2pyr reported by Norbury et al. (2). The perchlorate in all three solid compounds would be presumably ionic.

The infrared (i.r.) spectra of the three com- pounds (Table 2) tend to confirm these structural

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TABLE 3. Electronic spectra*

Frequency (nm)

Ligand band Metal d and d band

Complex Chloroform Nujol Chloroform Nufol

*Electronic spectra were taken by Miss M. Tong on a Hitachi SP3-T spectrophotometer, both in solution and as Nujol mulls. Numbers in parentheses are molar extinction coefficients.

t ln chloroform solution, this compound gives rise to a green solution. $Very weak absorption.

assignments. Free ligand peaks were observed in Nujol and CHCl, (or CH,Cl,) for NiL,- (H,O),(ClO,),, although they are not well- defined in KBr. Assignment of these peaks is based on that for the corresponding pyridine complexes (2, 5). The water peaks in both this compound and NiL,(H,O),(ClO,), are within the range of those for lattice water (v,:3465- 3407 cm-l) (6), indicating that the water is at most weakly bound to the metal. The thermal data in Table 1 also confirms this observation. Comparing the spectra in the perchlorate region with that of Ni(C104),.6H,0 (7, 8) in KBr and Nujol one can conclude that the perchlorate in all cases is ionic in solid state although there is some activation of the v, mode and splitting of the v, mode, presumably due to the effects of low site symmetry of the crystal lattice. How- ever, in CH,Cl, or CHCl, solutions, the spectra show that coordination of the perchlorate to the metal ion has taken place in all three com- pounds as the result of removal of this lattice effect in solution. The far infrared of the blue compounds show some unassigned peaks in the region 225-240 cm-l, and could be an indi- cation of a weaker Ni-N bond resulting from a constrained ligand conformation imposed by the waters at the octahedral positions. Similar peaks were observed in the compounds Ni(y-pic),Cl, and Ni(y-pic),Br, (3).

The electronic spectral data (Table 3) are consistent with a change from a square planar configuration in the yellow NiL4(C1O4), to an octahedral geometry in the other two cases.

The conductance data (Table l), taken in methylene chloride, indicate that 0.01 M solu-

tions of all the complexes are very little ionized indicating coordination of the perchlorate in solution, consistent with the i.r. solution data. The solutions of these compounds, when satu- rated with water, increase these values only slightly; apparently the small amount of water thus added competes equally well with y-pico- line for the metal. The yellow compound dis- solved in y-picoline as solvent, shows a large increase in conductance consistent with in- creased concentrations of NiL,'", ClC0,-, and NiL,'". Upon heating and cooling, the solution turned yellow-green and the conduc- tance increased even further, consistent with the greater stability of NiL,'" over NiL,'".

The complex NiL6(H,O),(C10,), has been turned over to Dr. H. Lynton of this depart- ment for an X-ray crystallographic determination of its structure.

The continued financial support of the National Research Council of Canada and the award of a U.N.B. demonstratorship to M. S. Sun are gratefully acknowl- edged. Thanks are also extended to Mr. M. Sears and Miss M. Tong for recording some of the spectra.

1. L. M. VALLARMO, W. E. HILL, and J. V. QUEGLIANO. Inorg. Chem. 4, 1598 (1965).

2. A. H. NORBURY, E. A. RYDER, and R. F. WILLIAMS. J. Chem. Soc. A, 1439 (1967).

3. M. S. SUN. Unpublished data, this laboratory. 4. S. BUFFAGNI, L. M. VALLARINO, and J. V. QUEGLIANO.

Inorg. Chem. 3, 671 (1964). 5. N. S. GILL, R. H. NUITALL, D. E. SCAIFED, and D. W.

A. SHARP. J. Inorg. Nucl. Chem. 18, 79 (1961). 6. P. J. LUCCHESI and W. A. GLASSON. J. Am. Chem.

SOC. 78, 1347 (1956). 7. R. W. G. WYCKOFF. Crystal structures. Vol. 3. 2nd

ed. Interscience Publishers. p. 814. 8. C. D. WEST. Z. Krist. 91A, 480 (1935).

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