1598 L. M. VALLARINO, W. E. HILL, AND J. V. QUAGLIANO that the strong band in the visible region in COX^)-^ in the tetrahedral complexes may not be due to crystal field effects a t all. No attempt is therefore made to assign the spectral bands of the tetrahedral cobalt (11) complexes which seem to occur in chloride and bromide complexes only. Two other possible structures are an oxygen or a chloride bridged structure similar to those found in copper(I1) pyridine N-oxide complexes* and in Co(py),Cl, (violet) ,?” respectively. The infrared and magnetic susceptibility data, however, seem not to support these two types of bonding.4 Quite unexpectedly the halide complexes seem to maintain a tetrahedral structure in N,X-dimethylformamide21(Figure 2). This may be due to a mechanism similar to t h a t observed by Buffagni and D u m z 2for CoC1, in dimethylformamide. It seems reasonable t h a t a similar displacement occurs with the CoX2Lp complexes ( X = C1, Br).
+ DMF COXZLZ + 2DMF CoX2L2
+ X+ 2X-
[COXL~DMF +] [ C O L DMF)2] ~( +*
This does not occur in methanol, since its coordina(20) J. N. Gill: R. S. S y h o l m , G. Barclag, T. I. Christie, and P. J. Pauling, J . I n o r g . ,V\iztcl. Chem., 18, 88 (1961) (21) F. A. Cotton and G . Wilkinson, “Advanced Inorganic Chemistry,” Interscience Publishers, New York, S , Y.,1962, p . 725, (22) S. Buffagni and T. 11. Dunn, J . Chem. SOL.,5105 (1961).
Inorganic Chemistry
tion tendency is smaller than t h a t of dimethylformamide. Nitrate Complexes.-The single-crystal X-ray analysisZ3of Co [(CH3)aPO]2(N03)2 has established t h a t the cobalt(I1) ion is surrounded by an irregular arrangement of six oxygen atoms, with each nitrate ion acting as a bidentate ligand. The spectra of the 2,6-DPNO and 2,4,6-TPNO cobalt(I1) nitrate complexes are similar to the spectra of Co [(CH3)3PO]2(N03)2. The absorption bands observed for these two nitrate complexes a t 565 and 320 m p were also observed for the above complex. The solids obey the Curie-Weiss law as shown by the determination of magnetic susceptibility a t different temperatures, and the effective magnetic moments fall in the same range as those of the triphenylphopshine oxide complexes.’b The spectra of the solid in lithium fluoride and in solution in nitromethane are superimposable except for the intensity, indicating that the complex does not change in the solvent (Figure 1). This seems to indicate t h a t the 2,6-DPKO and 2,4,6T P N O complexes also have distorted octahedral structures. Acknowledgment.-We appreciate the assistance provided by the Xational Science Foundation through a chemistry research instrument grant (GP-1690). (23) F. A. Cotton and R. H . Soderbei-g, J . A m . Chem. Soc., 85, 2402 (1963.)
CONTRIBUTION FROM THE DEPARTNEST OF CHEMISTRY, STATEUNIVERSITY, TALLAHASSEE, FLORIDA THE FLORIDA
Coordination Compounds of Nickel(I1) Salts with Substituted Pyridines. Complexes of 2-, 3-, and 4-Methylpyridine BY L M ’L’ALLAIIINO, 11’ E HILL,
AUD
J V QCAGLLkKO
Recezaed March ZF, 1965 Complexes of 2-, 3 - , and 4-methylpyridine (2-pic, a-pic, and 4-pic) with a number of Ni(I1) salts (chloride, bromide, iodide, nitrate, perchlorate, and tetrafluoroborate) were prepared and investigated. Three series of complexes were obtained, Ni(pic)Xz (pic = 2-pic, 3-pic; X = C1, B r ) ; Ni(pic)zXz(pic = 2-pic, 3-pic, 4-pic; X = C1, Br, I, N08); Ni(pic)aXz (pic = 3-pic, 4-pic; X = C1, Br, I, NOs, C104, BF4). The complex N i ( 3 - p i ~ ) ~( X ~= (2104, BF4) was obtained in two isomeric forms, identified as [ K i ( B - p i ~ ) ~and x ~ ][ N i ( 3 - ~ i c Xz, ) ~ ] respectively. The complexes of 4-aminopyridine, Ni(4-NHzpy)4Xr ( X = C1, Br, I, C104), were also prepared and investigated. The stoichiometry and stereochemistry of the complexes were correlated with the properties of the anion and ligand, in particular with the basicity and steric requirements of the latter.
Introduction This investigation is part of a study on the coordination compounds of substituted pyridines with Ni(I1) salts, to establish a correlation between the stoichiometry and stereochemistry of Ni(I1) complexes and the properties of the ligands and anions. Some previous results of this study have been p ~ b l i s h e d . l - ~ The (1) Sr. M. D . Glonek, C. Curran, and 5. T. Quagliano, J . Am. Chem. Soc., 84, 2014 (1962j. (2) S. Buffagni, I,. 11.Vallarino, and J. V. Quagliano, 1iioi.g. Ciwiiz., 3, 34s)
(1961). (3) S . Buffagni, L. M. Vallarino, and J. V. Quagliano, i b i d . , 3, 671 (1964).
present paper describes the preparation and properties of the complexes of isomeric methylpyridines (picolines, abbreviated as a-pic, %pic, and 4-pic) with a number of Iii(I1) salts. The analogous complexes of 4aminopyridine are also reported, as they are helpful in establishing a correlation between the stereochemistry of the KiL4X2complexes and the basicity of the ligand L. Experimental Starting Materials.-The picolines (Brothers Chemical Co.) were dried over potassium hydroxide for 3 days, distilled under
Vol. 4 , No. 11, November 1965
COORDINATION COMPOUNDS OF NICKEL(II) SALTS 1599 TABLE I
ANALYTICAL DATAFOR Pefi,
Compounda
Color Brick-red (Ni(2-pic)Clzl [Ni(2-pic)eClz] Deep blue Pale yellow-green (Ni(3-pic)aCh), (Ni(3-pic)Brz), Brick-red [Ni(Z-pic)aBrz] Deep blue Yellow (Ni(3-pic)aBrz)7z Yellow {Ni(B-pic)aBrz} Dark green [Ni (%pic)2 1 2 1 [Ni(3-pic)2Iz] Dark green Dark green [Ni(4-pic)212] Blue-green [Ni(3-pic)aClz] [Ni(4-pic)iCIz] Pale blue Blue-green [Ni(B-pic)aBrz] Pale blue [Ni (4-pic)aBrzI Yellow-green [Ni(3-pic)aIzl Yellow-green [Ni(4-pic)aIzl Green [Ni(%pic)z) NOa)z I [Ni(3-pic) a(N0a)a ] Blue [Ni (4-pic)a(KOa)zl Blue Yellow [Ni(3-pic)41(C1Oa)r [Ni(3-pic)r(C104)1 Blue Yellow [Ni(B-pic)r](BF4)a [Ni(3-pic)a(BFi)nl Blue Bright yellow [Ni(4-pic)rl (c1Oa)z Bright yellow [Ni(4-pic)al (BF4)Z Blue [Ni(HzO)z(3-pic~~l(ClOa~z Blue [Ni(HzO)a(3-pic)rl(BF4)Z [Ni(HzO)z(4-pic)rI (ClOda Blue Blue [Ni(HzO)z(4-pic)a](BF4)z Orange [Ni(4-NHzpy)alCIz Blue [Ni(4-NHzpy)rCIz I [Ni(4-NHzpy)a IBrz Orange Blue-green [Ni(4-NHz)4Brzl [Ni(4-NHzpy)alIz Orange Yellow (Ni(4-NHzpy)rl(ClO~)a a 2-pic = 2-methylpyridine, 3-pic corrections were made.
=
B.M.~ 3.44 3.48 3.39 3.19 3.47 3.43
3.38 Diamag. 3.47 3.38 3.15 3.28 3.17 3.30 3.21 3.34 3.23 3.13 3.31 Diamag. 3.14 Diamag. 3.18 Diamag. Diamag. 3.23 3.09 3.13 3.16 Diamag. 3.18 Diamag. 3.26 Diamag. Diamag.
THE
NICKEL( II)-PICOL~NE COMPLEXES
--Ni, Calcd.
%-
26.35 18.58 18.58 18.84 14.50 14.50 14.50 11.77 11.77 11.77 11.69 11.69 9.93 9.93 8.57 8.57 15.95 12.70 10.57 9.32 9.32 9.71 9.71 9.32 9.71 8.81 9.16 8.81 9.16 11.60
26.20 18.36 18.39 18.40 14.46 14.70 14.33 11.85 11,62 11.41 11.73 11.85
11.60 9,86 9.86 8.51 9.25
Found
9.98 9.53 8.52 8.49 15.40 12.50 10.43 9.31 9.31 9.65 9.65 9.07 9.55 8.46 9.02 8.95 9.25 11.21 11.81 9.83 9.73 8.56 9.47
Halogen, % Calcd. Found
--N, Calcd
31.84 22.45 22.45 51.35 39.48 39.48 39.48 50.89 50.89 50.89 14.12 14.12 27.04 27.04 37.05 37.05
6.29 8.87 8.87 4.49 6.92 6.92 6.92 5.62 5.62 5.62 11.16 11.16 9.48 9.48
14.01 14.01 26.86 26.86 36.83
31.58 22.56 22.56 51.28 39.46 39.59 39.39 50.38 50.83 50.75 14.11 14.01 26.90 27.29 36.98 37.20
14.12 13.90 26.95 27.06 36.50
8.18 8.18 15.19 15.14 15.14 8.89 8.89 9.27 9.27 8.89 9.27 8.41 8.74 8.41 8.74 22.13 22.13 18.82 18.82 16.25 17.38
%-Found 6.25 8.53 8.75 4.32 6.78 6.84 7.10 5.84 5.80 5.67 11.32
(4) J. H. S. Green, W. Kynaston, and H. M. Paisley, S+cctrochiitz. A d a , 19, 549 (1963). (5) J. D. S. Goulden, J. Chem. Soc., 2939 (1952).
Found
--H, %Calcd. Found
45.62
45.41
4.48
4.37
35.60 28.89 28,89
36.10 28.80 28.12
3.49 2.83 2.83
3.60 2.90 3.13
57.40
57.66
5.63
5.66
48.76 48.76 42.07 42.07
49,04 46.39 41.48 42.06
4.78 4.76 4.13 4.13
4.79 4.72 4.13 4.25
11.18 9.67 9.32 7.94 7.72 15.62 15.52 15.45 8.75 8.75 9.35 9.35 8.69 9.23 8.28 8.55 8.39 8.70 22.05 22.15 18.75 18.68 16.50 17.64
3-methylpyridine, 4-pic = 4-methylpyridine, 4-NHzpy
reduced pressure, and stored over molecular sieves. The 4aminopyridine (abbreviated as 4-NH~py)(Aldrich Chem. Co.) was purified by chromatography over alumina (Wohelm grade 1) in benzene solution. The boiling and melting points and infrared spectra of the purified compounds were in good agreement with those reported in the literat~re.~25 Preparation of the Complexes.-The compounds prepared, together with their colors, magnetic moments, and analytical data, arelisted in Table I. The complexes of the general formula [Ni(pic)4Xz] (pic = 3-pic and 4-pic; X = C1, Br, I ) were prepared by the dropwise addition of an excess of the picoline to a boiling solution of the anhydrous nickel( 11) halide in ethanol, under constant stirring. The precipitate which formed immediately or on cooling was filtered off, washed with cold ethanol, and dried in vacuo over P ~ O I O The . chloro and bromo complexes were recrystallized by dissolution in dichloromethane containing a small amount of the picoline and reprecipitated with ethyl ether. The iodo complexes were not recrystallized. The complexes [Ni(2-pic)~Clz]and [N3(2-pic)~Br2]were obtained as previously described'; [Ni(2-pic)~Iz]was prepared similarly to the [Ni(pic)4X~]compounds, except that it was not washed nor recrystallized. I t was dried in vacuo over P4010. The complexes { Ni(3-pic)~Br~],and [Ni(4-pic)~I~] were prepared by heating the finely powdered corresponding complexes of the type [Ni(pic)dX~]a t 110" under vacuum. The heating times required for complete transformation were 2 hr. for {Ni(3pic)zBrs}, and 1 day for [Ni(4-pic)?Iz]. The complex [Ni(3pic)zIZ]was prepared by heating [Ni(3-pic)&] in an oven a t 90" for 3 days. The complexes { Ni(4-pic)~Br~),and { Ni(3-pic)~C1~},were prepared by the dropwise addition, with constant stirring, of a
Calcd.
=
4-aminopyridine.
Diamagnetic
dilute ethanol solution of picoline ( 2 moles) to a boiling ethanol solution of nickel(I1) halide (1 mole). The precipitate which formed was filtered off, washed with hot ethanol, and dried in vacuo over P4O10. The {Ni(3-pic)Brz}, complex was prepared by heating the finely ground [Ni(3-pi~)~Brz] in an oven a t 90" for 5 days. TO obtain a homogeneous product, frequent stirring and regrinding of the powder was necessary. The complex {Ni(2-pic)Cl~}, was obtained by repeatedly washing [Ni(B-pic)~Cl]with ethyl ether. The complex [ N i ( 2 - ~ i c )N08)2] ~( was prepared by the addition of excess picoline to an ethanol solution of anhydrous nickel( 11) nitrate. The solution was diluted with ethyl ether and cooled in a refrigerator; crystals precipitated which were filtered off, washed with ethyl ether, and dried in vacuo over P4010. The complexes [Ni(3-pic)a(SO3)2]and [Ni(4-pic)4(N08)2] were obtained by concentrating almost to dryness, under reduced pressure, an ethanol solution of anhydrous Ni( 11) nitrate containing excess picoline. The compounds were dried in vacuo over P4OlO. The complexes [Ni(4-pic)4]X1 ( X = clod, BF4) were obtained by the addition of ethyl ether to an ethanol solution of the corresponding aquo complex [Ni(HzO)s]Xp, containing an excess of picoline. The compounds were repeatedly washed with ethyl ether and dried in vacuo over P4010. The complexes [Ni(H~0)2(4-pic)4]X? ( X = C104, BF4) were prepared by the slow evaporation of a solution of the corresponding [Ni(il-pic)d]Xzin dichloromethane saturated with water. The compounds were dried in air a t room temperature for 1 day. The complexes [ N ~ ( H Z O ) Z ( ~ - ~ (~XC )=~ ]NOS, X Z c104, BFa) were obtained by the addition of ethyl ether to an ethanol solution of the corresponding [Ni(HzO)s]Xz, containing an excess of picoline. The compounds were repeatedly washed with ether and dried in vacuo over P4O10. The complexes [Ni(S-pic)a](C104)a and [Ni(3-pic)4]( B F ~ )were z
1600 L. M .
brALLARINO,
w.E. HILL, AND J. 'v. QUAGLIANO
prepared by heating the corresponding [Ni(HzO)2(3-pic)d]X~in wacuo a t 110 and SOo, respectively.
The complexes [Ni(3 - ~ i c )C104)2] ~( and [Si(3-pic)4(B F ~ ) P ] were prepared by refluxing for 1 hr. the corresponding [Xi( H ~ O ) ~ ( 3 - p i c )in ~ ]aX1~: 1 mixture of benzene and 2,2-dimethoxypropane. After cooling the solution in a refrigerator overnight large crystals separated which were filtered and dried in wacuo. The yellow-orange complexes [Si(.l-NH*py)a]X2 ( X = Br, I, Clod) and the greenish blue [Ni(4-SHzpy)4Clz]mere prepared by heating on a steam bath an ethanol solution of anhydrous nickel(11) halide, or [ru'i(H~0)6](C104)~, containing an excess of 4aminopyridine. The yellow crystals which formed were separated by decantation from a small amount of a powdery greenish impurity, washed several times with ethanol, and dried in vucuo. The yellow-orange complex [Ni(4-h7H2py)~] BrP on standing 2 days in a desiccator changed into the greenish blue [iYi(4XH2py)4Br~] . The reaction of hTiCIP with 4-aminopyricline in ethanol a t -20" yielded golden yellow needles which rapidly changed to the greenish blue [Si(4-SHzpy),Clz]. Stability toward Atmospheric Moisture .-The complexes [Si(3p i ~ ) ~ ](X X ~= Clod, BFI) and [Ni(X-pic)4X2] ( X = I , Clod, BF4) are very sensitive to moisture, which transforms them into XP. The complexes { Si(2the Corresponding [Ni(H~O)~(3-pic)a] pic)Ch}, and [,\ii(2-pic)~X~] ( X = C1, Br, I, S O S )react rapidly with moisture t o give greenish amorphous decomposition products. These moisture sensitive compounds were prepared and handled in a drybox. The complexes [hTi(3-pic)3(N03)2] and [Xi(4-pic)4X2] ( X = I, NOS) are only moderately sensitive to moisture. All other complexes are fairly stable but decompose on prolonged exposure. Analyses.-Halogcns were determined by the Volhard method, nickel by titration with EDTA, nitrogen by the semimicro D u p a s method, and carbon and hydrogen by microanalyses. Magnetic susceptibility measurements were made by the Gouy method. T h e values of the magnetic moment, p e f f ,of the solid compounds are listed in Table I. Infrared absorption spectra were taken with a Perkin-Elmer Model 221 recording spectrophotometer. T h e spectra of the solid complexes were obtained both in Nujol mulls and in KBr disks. The absorption frequencies are reported elsewhere.6 Electronic Spectra.-Transmission spectra were taken both in solution and in Nujol mull with a Cary Model 14 recording spectrophotometer. Diffuse reflectance spectra of the finely powdered solids mere obtained with a Bcckman Model DU quartz spectrophotometer equipped with a diffuse reflectance attachment, using magnesium carbonate as the reference. For the solid compounds, poor resolution was generally obtained beloiv 10,000 cm. -l and therefore in the spectra of the octahedral complexes the band corresponding t o the transition 3Tz was .not observed. The absorptiou maxima of the solid complexes, of the dichloromethane solutions, and of solutions containing added amounts of picolines are reported elsewhere.6 Conductivity measurements were made at 2Fj0 by the standard procedure using Spectrograde dichloromethane as the solvent. The following values were obtained (Ah? in ohm-' cm.2 mole-'): CH2C12, specific conductivity ohm-' cm.-'; CH~CIP 4-pic (10.0 M ) , specific conductivity
