HANSB.
4232
JONASSEX XXD
ELWOOD J. GONZALES
+ + +
three complexes the maximum slope found in the
Complexl 3H+ f Complex2 f 3H' f Complex3 3 H - -IComplex4 3Ht f
pH regions of about 3 t o 6 corresponded to a value of 3 for z. Considering the species of the protonated amines existing in the pH regions of the study the following reactions are indicated : For the Cu(I1)-trien complexes with decreasing pH two reactions may occur Complexl f 3 H + Complex2 3H+
+
+ %e+Cuo + trien 1H'+ + 2e +Cuo + trien 3H3+ 7
2e +Cuo %e--+ Cuo 2e --+ CuO 2e --+ Cuo
VOl. 79
+ hexen 6 H 6 +
+ hexen 5H5+ t + hexen 4H4+ + hexen 3H3+ I decreasing PH
If Complexl ComplexJ Complex, Complexl
= = = =
CuH3hexen5 CuHzhexen4 CuHhexen3+ Cuhexen2-
decreasing PH
This would fit the data if Complexl = [CuHtrienI3+and Complex? = [Cutrien]?+ For the Cu(I1)-tetren complex these three reactions fit the data. Complex-1 f 3 H + Complex? 3H+ Complex3 3H+
+ +
+ 2e Cuu q- tetren 5Hj+ %e+Cuo + tetren 4Hl+ f + %e--+ Cu" + tetren 3H3+ 1 ---f
decreasing PH
if Complexl = C u H l t e t r e n Complex2 = CuHtetren3Complex3 = Cutetrenz+
For the Cu(I1)-hexen system four reactions would explain the data
[COSTRIBUTIOSFROM
THE
This also seems to indicate that three of the copper to amine bonds in the copper(I1) polyethyleneamine complexes are of about the same order of strength, far greater than the strength of the proton t o amine bond. The other copper to amine bonds are of about the same order of strength as the proton to amine bond and an equilibrium is set up between them. At least three of the amine groups are bound to the copper(I1) ion, the rest are protonated depending upon the pH of the medium. Acknowledgment.-The financial support of part of this work by the Office of Ordnance Research, U. s.Army, is gratefully acknowledged. SEW ORLEASS,LA.
RICHARDSOS CHEMISTRY LABORATORY AT TULAVE USIVERSITY]
Studies of Metallated Dye Complexes. 111. Cogper(I1)-o-Azophenol Complexes B Y HANSB.JOXASSEN AND E L \ l 7 O o D J. GONZALES' RECEIVEDAPRIL22, 1957 Spectrophotometric and conductometric evidence indicates that the copper(I1)-o-azophellol complex forms a copper(I1) complex with propylene glycol in alkali in which the glycol and copDer(I1)-dye react in a 1 1 mole ratio The complexes K[Cu-o-azophenol-OH] and Cu(II)-o-azophenol-H20 were isolated from ethanolic solution.
Introduction o-Xzophenol, a dye containing hydroxy groups ortho to the azo group, readily forms a dye complex with transition metal ions in which the metal ion is bound to the two oxygen atoms and to the azo linkage as shown by investigations of Morgan lo and co-workers,2-8 Drew and L a n d q ~ i s tLTTilson, ,~ and Oliver.l 1 In the present investigation dihydroxy compounds, propylene glycol (pngl) and I-2,3-butanediolj having free rotation of the hydroxy groups, are used t o show their effect on the unsaturation of the copper(I1) complex coordination sphere. Experimental (99+ ci> pure), white label, EastA . Reagents.-Pngl man Kodak Company was used without further purification. [ I ) Abstracted in part from a thesis submitted by Elwood J G u n zales t o t h e Tulane University i n partial fulfillment of the requirementi fr,r t h e degree of hl;i.ter [ i f Science ( 2 ) G T. 1 f o i g a n a n r l J I3 Xfain-Smith. J C h e m S o c , 7 0 t ( 1 9 2 1 ) . (,'O 36.14 (sample popped slightly on combustion due t o the -N=Nlinkage). ( 2 ) [Cu(I1)-dye-H~0].-A second compound was isolated by mixing 50 ml. of the pure pngl and 0.6 g. of the dye. The whole was stirred until some of the dye dissolved m the pngl. Then 1 g. of Cu(N03)* in 20 ml. of distilled water and 40 ml. of 95% ethanol was added. The solution immediately turned deep red. The whole was stirred and dissolved on the hot plate for 15 minutes. Filtration and dilution t o 300 ml. with distilled water with subsequent slow evaporation to 100 ml. gave a brownish-red solution. Dilution to 200 ml. with distilled water and cooling in an ice-salt bath gave a brownish-black precipitate. The filtered and washed precipitate was dried in a 110" oven for 2 hours. A n d . Calcd. for [Cu(II)-dye-H~0]: C, 49.00; H , 3.43; N, 9.54; ash, 27.08 (as CuO). Found: C, 49.18; H , 3.15; N, 9.54; ash, 27.00 (as CuO).
Discussion and Results A. Spectrophotometric Studies.-The spectrophotometric titration in Fig. 1 indicates t h a t no change in absorption occurs until the two hydrogen ions liberated in the copper(I1)-o-azophenol interaction have been neutralized. No sharp break is noted after two equivalents of KOH have been added such as was observed in the Jonassen, Cook and Wilson investigation. l 4 Hence seemingly no Cu(II)-dye-hydroxy complex forms in the presence of pngl. The change in slope occurring near 2.5 equivalents KOH is similar to a weak acid-strong base type interaction which the pngl-KOH reaction is. The pngl thus seems capable of coordinating with the Cu(I1)-dye complex. Nine equivalents of KOH are necessary to produce maximum absorption without formation of a precipitate. I n Wilson's studies,14 in the absence of pngl, seven equivalents of KOH are needed to give the maximum absorption without precipitation. If the same reaction mechanism is assumed as in i.e., addition of OH- ions Wilson's in~estigation,'~ to give the hydroxy complex which then decomposes to [Cu(OH)6I3-, then the additional two hydroxide ions in this investigation must have reacted with the pngl giving first the [copper(II)dye-pngl ] 2 - complex which then decomposes a t (13) L. Segal, Doctoral Dissertation, Tulane University, 1954. JOURNAL, (14) H. B. Jonassen. M . M. Cook and J. S. Wilson, THIS 73,4083 (1951).
4283
2 4 6 8 10 Equiv. KOH/mole Cu( 11)-dye and pngl. Fig. 1.-Spectrophotometric titration: 0.01 mmole copper( 11)-o-azophenol 0.01 mmole propylene glycol with 0.1119 M KOH; wave length, 525 mp; temperature, 25-26".
+
high OH- ion concentration again to the [Cu(OH)6l3- ion. Although alcoholic hydrogens generally are not acidic, if the oxygen atoms coordinate, however, such as to a copper(I1) ion in the dye complex, the resulting shift in electron density would weaken the oxygen-hydrogen bond giving enhanced acid characteristics such as reaction between tartrate and copper(I1) ion in Fehling solution. If the other oxygen of the pngl behaves similarly, then two OH- ions would be required if the pngl reacted as a bidentate ligand which would indicate a five coordinated [~opper(TI)-dye-pngl]~- complex proposed from the titration data. The sixth position of the copper(I1) coordination sphere may be occupied by a solvent molecule. The pngl and copper(I1)-dye interaction with base may be shown as Cu(I1)-dye
+ pngl + 2 0 H -
+
[ C ~ ( I I ) - d y e - p n g l ] ~ - 2 H 2 0 (I)
with decomposition of the pngl complex as further OH- ion is added [ C ~ ( I I ) - d y e - p n g l ] ~f - 50H-J[Cu(OH)s13- f dye ion f pngl ion
(11)
Evidence for the presence of a copper(I1)-dyehydroxy complex in the absence of pngl is indicated by inspection of curve A, Fig. 2. The first value is 1.8
.-L"L 1.7 ci
z
a
Y
0"
1.6
1
2 3 4 5 Equiv. KOH. Fig. 2.-Effect of alkali on the copper( 11)-o-azophenol propylene glycol systems; and the copper(I1)-o-azophenol Curve A, wave length, 510 mp; temperature, 25-26'. points 1 and 2 contain 0.01 mmole copper(I1)-o-azophenol; curve A, point 3 and curve B, points 1, 2, and 3 contain 0.01 mmole copper(I1)-o-azophenol plus 0.01 mmole propylene glycol.
+
HANSB.
4284
JONASSEN AND
the absorption for the copper(I1)-dye complex after the two OH- ions are added to neutralize the Hf ions for the copper(II)-dye interaction. The second value shows increased absorption for this complex in basic solution where a copper(I1)-dyehydroxy species may be present. When, however, pngl is added to the copper(I1)dye complex in the same concentration of alkali, the absorbancy increases again (point 3), suggesting a pngl complex. Such interaction is also indicated in curve B, Fig. 2 where, t o equivalent quantities of copper(I1)dye and pngl, additions of the same 4 equivalents of OH- ion cause increases in absorption t o the same value. Addition of 5 equivalents of OHion leads t o point 3, curve B. B. Conductometric Titration Studies.-Titration for a 1:l molar ratio of the copper(I1)-dye and pngl with KOH (curve A, Fig. 3 ) exhibits two
L
IB
I(1
-X w. s.0 $ -
I n the preparation of K[Cu-dye-OH] small quantities of distilled water were used. High base concentration in the method results in the anionic complex having a coordinated OH group. A second compound, [Cu(II)-dye-H20], isolated by using large amounts of water resulted in a coordinated H2O molecule. Depending on the method employed, the reactions may be Cu(OH)*
+ dye + KOH
-7 1
4
2 A = equiv. KOHjmole Cu(I1)-dye and pngl B = moles pngl/mole Cu(I1)-dye. B
K[Cu-dye-OH]
+ 2H20
(111)
and Cu(KOa)?f dye
+ Hg0 [Cu(II)-dye-H20]
+ 2HN03
(IV)
These compounds were found to be quite soluble in formamide and pngl. Determination of their absorption values a t the wave length noted in Table I indicates the hydroxy complex in formamide has greater absorption than the aquo complex in the same solvent. This agrees with the data of curve A, Fig. 2, in which the dye complex in excess alkali also has greater absorption indicating a hydroxy complex. TABLE I
8.1
7.9 c:
VOl. 79
ELWOOD J. GONZALES
System
1 1 2 2 2 2
X
Jf K[Cu-dye-OH]" X lo-' Jf [Cu(II)-dye-H20]" X 10-5 ,'if K[Cu-dye-OH]" X lo-' X K[Cu-dye-OH]* x lo-" .1C [Cu(II)-dye--H~O]" x -1f [Cu(II)-dye-H~0]* In formamide. * In pngl.
m+
Optical density
510 510 510 510 510 510
1.900 1.700 0.278 ,382 .328 ,337
If the isolated compounds of same concentrations are dissolved in formamide and in pngl, the absorpFig. 3.-Conductometric titrations at 30": curve A, 0.05 tion values (Table I) are greater in both instances Inmole copper(I1)-o-azophenol in 0.05 mmole prop>-lene when prig1 is added which might be another conglycol with 0.1119 M K O H ; curve E , 0.05mmolecopper(II)firmation of pngl complexes. Furthermore, since o-azophenol ill 0.20 mmole KOH with 0.0236 Jf propylene the difference in optical densities in formamide and glycol. pngl for the hydroxy complex is a t least tenfold over that of the aquo compound, this indicates the breaks: the first a t the neutralization of the two OH group is necessary in pngl ion formation. hydrogen ions liberated in the copper(I1)-dye I t was also attempted to follow the complexing reaction. The second break occurs a t about four reaction polarimetrically by using 2-2,3-butanediol, OH- ions. This inflection after two more OH- an optically active glycol. If the concentration of ions are added, which occurs also in the spectro- the glycol is kept constant, then the change in opphotometric titration, confirms the interpretation tical activity would be due to the optical activity given for the titration data. The reverse titration of a solution containing one of the [copper(II)-dye-glycol]?- complex. T o facilitate visual observation solutions 1 X 10-5 -11 mole of copper(I1)-dye and four equivalents of in copper(I1)--dye and 3 X lop4 31 in glycol were KOH with the pngl (curve B, Fig. 3) shows a break after one mole of pngl has been added, con- used but the changes in activity were too small t o be measured accurately. firming the above results. Acknowledgment.--The financial support of the t o preC. Isolation of Complexes.-Attempts pare the pngl complex were unsuccessful. Condi- Research Corporation and the American Cyanamid Company for this work is gratefully acknowledged. tions used resulted in the products K [Cu-dye-OH] S E W O R L E A S S 18, LOLW31.4NA and [Cu(II)-dye-H20 I.
