June 5, 1959
S P E C T R A OF SOME
CHROMIUM(II1) 2-METHYL-1,2-PROPANEDIAMINEC O M P L E X E S
TABLE IV SUMMARY OF DIFFERENCES IN 2 LOGKayFOR Ni(II), Pb(I1) AND Zn(I1) WITH A NUMBER OF REAGENTS Metal ions compared and relative stability order
Reagent
Difference in 2 log K I I at 26.0
P b > Zn 0.5 Zn > P b 0.6“ o-.4minobenzenethio11* P b > Zn 1.3 o-Aminophenol14 Zn > P b 0.7 6-Mercaptopurine Zn > S i 1.4 6-H ydroxypurine Zn 2 Ni 2.3“ o-Aminophenol l 4 N i > Zn 0.2 Mercaptoacetic acid16 Zn > Ni 1.5b 6-Mercaptopropionic acidlg Zn > Ni 3.9 6-Aminopurine Zn b Ni 0.4“ Ammoniaz Zn > Ni 1 2b*c a Hydrolysis interferes. In water. At 30’ in water. 6-Mercaptopurine 6-H ydroxypurine
P b > Zn > Ni > Co and for 6-hydroxypurine: Cu > Zn, Ni > Pb. The change in the relative position of lead and zinc in these two compounds is similar to that which
2610
was reported by Charles and Freiser with oaminobenzenethiol and o-aminophenol, l 4 and would seem to reflect a general trend in sulfur-containing reagents. Concerning the relative positions of zinc and nickel in the 6-mercaptopurine sequence the order may also be attributed to the participation of the sulfur atom in the bonding of the purine-metal complex. Further evidence that zinc(I1) forms a stronger complex than nickel(I1) when sulfur is involved in the ligandmetal bond has been presented by Leussingl8 on the stabilities of mercaptoacetic acid-metal complexes and by Fernando and FreiserIg on the stabilities of P-mercaptopropionic acid-metal complexes. Acknowledgment.-The authors gratefully acknowledge the financial assistance of the U. S. Public Health Service. (18) D . L. Leussing, Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, hlarch, 1958. (19) Q. Fernando and H. Freiser, THISJOURNAL, 80, 4928 (1958).
PITTSBURGH, PA.
[CONTRIBUTION FROM THE DEPARTMENT O F CHEMISTRY OF THE UNIVERSITY OF CALIFORXIA, LOS ANGELES]
Synthesis and Spectra of Some Chromium(II1) Complexes with 2-Methyl-l,2propanediamine lapb
BY KNUDG. POULSEN~~ AND CLIFFORD S. GARNER RECEIVEDDECEMBER 8, 1958 Conventional methods for the synthesis of tris-(ethylenediamine)-chromium(111) compounds (and some propylenediamine analogs), when isobutylenediamine (ibn) is used instead of ethylenediamine, generally have been found either to give no reaction or to yield bis-( ibn) complexes. Five new complex compounds have been isolated and characteriz d by chemical analyses and spectral methods: trans-[Cr(ibn)~( NCS)Z]SCN, ox(ibn)Cr-ox-Cr(ibn)ox, [H~O(ibn)Xr-O-Cr(ibn)zH~O] ( S O ~ ) ~ . ~ H [(ibn)*Cr-(OH)~-Cr(ibn)z]( ZO, C104)r and [(ibn)~Cr-(OH)2-Cr(ibn)~] Clr. Spectral studies have shown that the latter complex undergoes interesting spectral transformations in aqueous solutions made weakly basic, similar to changes exhibited in the rapid conversion of the acidic rhodo cation to basic rhodo.cation and the slower subsequent change to the erythro ion. Evidence was obtained for the existence of the Cr(ibn)a+8ion. Chromium(II1) forms complexes with ibn much less readily than with ethylenediamine or propylenediamine. The tendency of chromium( 111) amines to form “01” or “diol” bridges is greatly accentuated with ibn.
Chromium(II1) complexes with ibn are of interest because this unsymmetric, optically inactive 1,2-diamine ligand implies the possible existence of eight diacidobis-(ibn) isomers (2 trans and 3 pairs of d- and I-cis isomers), possibly permitting a distinction among different mechanisms of substitution and isomerization reactions of chromium complexes. Apparently no such complexes have been reported in the literature, although compounds of Co(III),*J Ni(II),4 C U ( I I ) , ~ Pd(II)6r6and Pt(II)6n7
-
with ibn have been described. From studies8-l1 of some chromium(II1) and many cobalt(II1) complexes with en, C-substituted en and diamines with three or more methylene groups between the two amine groups, the stability of the complexes with five-membered chelate rings is knownl1-l3 to be much greater than for complexes with six or more atoms in the ring. Alkyl substitution a t the carbon atoms usually affects only slightly the complexing properties of the 1,2-diamines (evidence mainly from cobalt complexes), whereas large effects are sometimes encountered with similar Csubstitutions in 1,3-diamines, as for 2,2-dimethyl1,3-propanediamine (neopentanediamine) , a much
(1) (a) Abbreviations used: ibn 2-methyl-1,2-propanediamine (isobutylenediamine); pn = 1,2-propanediamine (propylenediamine): en ethylenediamine: p y pyridine: ox oxalato. (b) Work partly supported under Contract AT(ll-1)-34, Project 12, between the U. S . Atomic Energy Commission and the University. (c) On leave of absence from the Technical University of Denmark, Copenhagen, (8) F. Basolo, Chcm. Reus., 62, 459 (1953). (2) F. Basolo, THISJOURNAL, 7 6 , 227 (1953). (9) A. E. Martell and M . Calvin, “Chemistry of the Metal Chelate (3) R. G . Pearson, C. R. Boston and F. Basolo, ibid., 76, 3089 Compounds,” Prentice-Hall, Inc., New York, 9. Y., 1952. (1953). (10) J. C. Bailar, Jr. (editor), “The Chemistry of the Coardination (4) F. Basolo, Y. T. Chen and R. K. Murmann, i b i d . , 76, 956 Compounds,” Reinhold Publ. Corp., Kew York, N. Y . , 1956. (1954). (11) F. Basolo and R. G. Pearson, “hlechanisms of Inorganic Reac(5) A. G. Lidstone and W. H. Mills, J . Chcm. SOL,1754 (1939). tions,” John Wiley and Sons, Inc., New York. N.Y., 1958. (6) H.Reihlen and W. Htihn, A n n . , 489, 42 (1931). (12) C. L. Rollinson and J. C. Bailar, Jr., THIS JOURNAL, 66, 280 (7) H.D. K. Drew, F. S.H . Head and H. J. Tress, J . Chem. Sac., (1943). 1549 (1937). (13) J . C. Bailar, Jr., and J. B. K w k , ibid., 68, 232 (1946).
-
-
-
%l(i
KNUDG. POULSEK AND CLIFFORD S. GARNER
LTol.s1
better complexing agent than 1,3-propanediamine (trimethylenediamine) . I 3 Thus, one might expect by analogy that the l,%diamines en, pn and ibn would not differ significantly in their complexing with chromium(II1). We have attempted to prepare certain diacidobis- (ibn)-chromium(III) compounds in connection with kinetic studies of aquation and other reactions of the isomers of a given diacidobis-(ibn) cation. These attempts have revealed interesting differences between ibn on the one hand and en and pn on the other in their complex formation with chromium(111) and have resulted so far in the isolation of five new chromium(II1) complex compounds.
(ibn)-chromium(II1) cation was revealed by coniparison with the remarkably similar spectra of the tris-(en) and tris-(pn) salts in aqueous solution (Fig. 1). Attempts to precipitate the tris- (ibn) cation were unsuccessful except with potassium hexathiocyanatochromate(III), which gave a chocolate-colored solid, presuinably [Cr (ibn) [Cr(SCN)6]. *Addition of this solid to bismuth(II1) nitrate solution precipitated red Bi [Cr(SCN)c], leaving a yellow solution apparently containing the Cr(ibn)3+3 ion (in presence of excess Bi+3). Attempts to concentrate the tris-(ibn) solutions by cation-exchange resins are underway in the hope of ultimately isolating a solid tris- (ibn) compound. Anhydrous chromium(II1) iodide mixed with exResults and Discussion cess dried ibn gave an immediate red color, turning Thermal decomposition of tris-(en) -chromium red-yellow after 10 hr. a t 100'. Extraction with (111) compounds, catalyzed by ammonium salts,14 acetone, followed by evaporation, left only a red yields the cis- or trans-diacidobis-(en) salts depend- smear. Dissolution in acetone and addition of ing on the anion present. In order to obtain the tris- ether precipitated a yellow solid which formed a n (ibn) compounds required for attempts to prepare oil inside of several minutes on exposure to air. Tris-(py)-chromium(II1)chloride is a convenient the diacidobis- (ibn) complexes by the above method, we tried syntheses anlogous to those suc- starting material for preparing tris- (en)l6 and triscessful for the tris-(en) complexes (and tris-(pn) (pn)I6 compounds, and the tris-(diamines) l 8 of complexes in some cases). These methods involve 1,2-cyclohexanedianiine and 1,2qclopentanedireaction of the anhydrous diamine under suitable amine. W'e found that an excess of ibn reacts with conditions with an anhydrous chromium(II1) salt the tris-(py) compound on refluxing, as shown by such as the sulfate (or dehydrated chrome alum), the formation of red-violet solutions and the odor o f chloride, tris- (py)-chromium(II1) chloride, tris- py released from the original complex. No crys(en)-chromium (111) chloride and hexamminechro- talline compound could be isolated. Refluxing excess dried ibn for a t least 8 hr. with mium(II1) nitrate. However, treatment of these chromium compounds with excess dried ibn even tris-(en)-chromium[III) chloride or hexarntninefor several weeks a t temperatures up to 110' gave chromium(I1Ii nitrate gave no evidence of reacblue-violet bis- (ibn) complexes. Usually only oily tion. products resulted from attempts to isolate comIn an attempt to adapt the method of Jprgenpounds from the reaction mixtures. sen,lgused for preparing hexamininechromium(II1) When anhydrous chromium(II1) sulfate or chlo- chloride, we treated by this method solutions of ride was used, violet solids could be isolated, the chromium(I1) chloride (or acetate) with excess analyses and properties of which (see Spectra and ibn. Blue amines were formed, but upon oxidation Experimental) imply that previously unreported in the absence of air only violet solutions were obpolynuclear complexes with oxo or hydroxo bridges tained. were formed. The crystals obtained from the Anhydrous potassium hexathiocyanatochromatesulfate can be represented satisfactorily by the (111) reacts with pn to give the tris-(pn) thiocyaformula [HzO(ibn)2Cr-O-Cr(ibn)2H20](S04)2.7-nate,16whereas with en tvans-dithiocyanatobis-(en)H20,and those from the chloride by the formula chromiuin(II1) thiocyanate results, with only minute amounts of the tris-(en) thiocyanate being H 0 formed.*O IVith ibn, we were able to get only the analogous dithiocyanatobis-(ibn) compound. This X = C1-, Clod(ibn)?Cr( )Cr(ibnl2 X4, previously unreported complex is presumably one of the two possible trans isomers (no evidence was If charcoal was used as a catalyst (platinum black obtained for the presence of more than one of these was found ineffective) in the synthesis from anhy- two isomers) inasmuch as its absorption spectrum drous chromium(II1) chloride, small amounts of a strongly resembles those of the homologous trans en yellow complex were left after the violet compound and pn compounds (Fig. I) ; moreover, the aqueous formed was extracted with ethanol. Although the solution of the complex, when treated with chlorine yellow complex was produced in very low yields a t O0, exhibited an absorption spectrum similar to and tended to disappear soon because of hy- that of trans-dichlorobis-(en)-chromium(II1)cntdrolysis, it could be extracted into ice-cold water ion and the analogous trans-pn complex, although acidified with hydrochloric acid (color changed isomerization during the chlorination cannot be exfairly rapidly to a red-violet if left alone). Cold cluded. The compound isomerizes and hydrodioxane could be added to slow the hydrolysis lyzes in aqueous solution a t separate measurable enough to allow taking the absorption spectrum. (in) P. Pfeifier, z.allorhn.che7,t., a4, 27s ( 1 ~ 0 0 ) . f l 6 ) P. Pfeiffer and ?VI. Haimnnn, Ber., 3 6 , 1063 (1903). The presence of the previously uiireported tris-
Ll
12. XI. Jaeger, Proc. A c u d . Sci. Amsterdam, 40, 108 (1937). (18) I:. 11. Jaeger and L. Bijkerk, Z.U I ~ O Y P C . h e m . , 233, 97 (19'171 (19) S. I f , Jgrgensen, J . prakt. C h e m . , [2] 3 0 , 1 (1881). i20) 1'. Pfeiffer, A w . , 54, 4 : i O R ( 1 N I l ) .
(171
(1-1) C I.. Rollinson and J. C. Bailar, Jr., "Inorganic Syntheses," Tal. TI, \IC..Fernelius. eilitur. 31cC7raw-Hill Book Co., Inc., S e \ v Y < r k , Y. x-,, l ! I l t i , 1, 1'111)
June 5, 1959
SPECTRA O F
SOXE CHRORlIUhI(III) 2-~JETHYL-1,2-PROPANEDI.-UIIKE COSIPLEXES
rates (we are currently studying the kinetics of these reactions), and loss of the third trans absorption band with concomitant formation of a typical cis spectrum (before aquation has occurred appreciably) is further evidence that the original complex is a trans isomer. Wernerz1 prepared cis-dichlorobis-(en)-chromium(II1) chloride from aqueous en and potassium trioxalatochromate(II1) by a series of steps leading through [C~-(en)~ox] [Cr(en) ox)^] to [Cr(en)zox]Cl, from which the desired compound was then made. When we followed this procedure, using ibn instead of en, we isolated in the first step a crystalline compound which we first assumed from its red-violet appearance and method of synthesis to be [Cr(ibn)Zox][Cr(ibn)(ox)z]. In the subsequent steps no crystalline solid could be isolated, however. Analysis of the red-violet compound gave results in good agreement with the composition ox(ibn) Crox-Cr(ibn)ox. That this previously unreported compound is a non-electrolyte is supported by the fact that none of i t is adsorbed from aqueous sohtion by Dowex 1-X8 anion-exchange resin and only a small amount is adsorbed by Dowex 50-X8 cation-exchange resin under conditions where these two resins adsorb [Cr(en),ox][Cr(en) ox)^] completely (splitting it 1 : 1 between the two resins). Absorption spectra are shown in Fig. 3. In another attempt to prepare diacidobis- (ibn)chromium(II1) complexes directly, we tried a 10% aqueous solution of ibn in place of a solution of en in treating dihydroxodiaquobis-(py)-chromium (111) chloride by the method of Pfeiffer,22which has been used successf u11y for preparing diacidobis- (en) complexes. The strong odor of py produced indicates that ibn can displace py from the complex, but solids could not be isolated from the sirupy violet mixtures obtained with ibn. I t is evident from all of the above that chromium(111) in general forms complexes much less readily with ibn then with en or pn. The apparent difficulty of forming tris-(ibn) compounds appears to be primarily a steric effect of the two methyl groups of ibn which make the introduction of a third ibn ligand on the chromium cation difficult (as is readily seen with Fischer-Hirschfelder molecular models) and not an effect of basicity since the base constants of ibnZ3are only slightly less than those of enz4 and pn.23 The tendency of chromium(II1) amines to form “01” or “diol” bridges appears to be greatly accentuated with ibn. Spectra of Luteo and trans-Dithiocyanatobis(diamino) Cations.-Curves A, B, C and D of Fig. 1 show the strong resemblance among the visible absorption spectra of the luteo ions in aqueous solution. Shapes of the spectra and relative positions of the two absorption maxima are the same, the spectra being only somewhat differently placed along the wave length scale. The relative wave lengths of the lower-energy (longer wave length) maximum for the four luteo ions are in (21) A. Werner, B e y . . 44, 3132 (1911). (22) P. Pfeiffer, ibid., 40, 3626 (1907). (23) F. Basolo, R . K. hlurmann and Y.T.Chen, THISJOURNAL, 76, 1476 (1953). (24) J. Bjerrum and P. Andersen K . Dairskt T.iduuck. .Fplsk. M a l h 1,s.
.\redd.,
22, S O .7 (1945).
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I
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I
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2617
, > 0
2
a
m a!
0 v)
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400 500 600 WAVELENGTH, mv, Fig. 1.-Absorption spectra of luteo and trans-dithiocyanatobis-(diamino) cations in aqueous solution: A, 0.0311 f [Cr(XH3)6](X03)R,(1.22); B, 0.0251 j’ ICr(en)3]C13, pH -3, (1.76); C, 0.0187 j’ [Cr(pn)3j(SCK)8,pH -3, (1.50); D, Cr(ibn)tY3in cold -1: 1 dioxane-water, PH -1, (1.39); E, 0.00700j’ t v a n s - [ C r ( e n ) * ( S C S ) 2 ] S C S(0.50); , F, 0.00660 f t r a n s - [ C r ( p n ) 2 ( S C S ) ~ ] S C ’(0.48); I:, G, 0.00507 f trans[Cr(ibn),( r\’CS)2]SCX, (0.45); numbers inside parentheses give the absorbancy a t the long wavelength maximum o f each curve.
agreement with our observation that en and pn, but not ibn, can displace ammonia from hexamminechroniium(II1) cation. This feature is also displayed by the spectra of the trans-dithiocyanatobis-(diamino) cations (curves E, F, G. Fig. 1). Spectra of Hydroxo-bridged Cations ; Effect of Base.-The hydroxo-bridged complexes of Fig. 2 exhibit certain interesting features. The strong similarity between the absorption spectra (curves D, .4) of the [(en),Cr-(OH)~-Cr(en),]+~ and [(ibn)?Cr-(OH)2-Cr(ibn)z]+ 4 cations in aqueous solution is additional support for the structure assigned to the latter ion. In weakly acid solution these two cations, together with the acidic rhodo complex, [(NH3)6Cr-OH-Cr(NH3)6]+5, undergo color changes when the solution is made weakly basic, the color changing a t once from red-violet to deep blue and then more slowly returning to nearly the original color. Recently, this change from the blue basic rhodo cation to the erythro product has been shownz6to be a replacement of one of the ten (25) W. E;. Wilmarth, H. Ckaff and S. T. Cnstin. Tins 2683 ( 1 4 X ) .
JOI:RNAT., 78,
K N U DG. POCLSEN AND CLIFFORD S. GARNER
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9
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300 1.5
1
SO0
700 300
500 I
I
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-
400 500 (io0 Wave length, m p . Fig. 3.--Absorpt1on spectra of oxalato complexes in aqueous solution: A , ox(ibn)Cr-ox-Cr(ibn)ox, satd. soln.; B, ICr(en)rox] [Cr(en)(ox)z], satd. soln.; C, Cr(en)zox+. eluted from Dowex 50-X8 resin with 6 f HCl; D, Cr(en)ox)^-, eluted from Dowex I-X8 resin with satd. SaSOa. 300
slow the reactions, spectra of the basic solutions of the en complex, and even the ibn complex, were measured a t - g o , although -25-S0~0 of the blue intermediates were converted before the spectra could be taken.) The splitting can be explained in terms of conversion of a hydroxo-bridge to an oxo 300 50 0 700 bridge, as is already known25 to occur with the WAVELENGTH, mu. change of the acidic rhodo ion to its basic form, Fig. 2.--Absorption spectra of hydroxo-bridged cations since the oxo oxygen atom will exert a much i n aqueous solution, showing effect of base (solutions cooled stronger effect on the 3d electrons of the chroto -5’ before being made basic, then measured a t once): mium atom.27 Since the splitting disappears in the ( a ) [(ibn)~Cr-(OH)&r(ibn)~]Cl~--il,-0.007 f complex in further reaction, the degree of symmetry in the original hydroxo-bridged complexes is presumably -0.1 f HCl (perchlorate salt gave same spectrum); B, made basic (pH -10); C, 2 hr. later; (b) [(en)zCr-(0H)z-Cr- regained in the final product, although it is not (en)~]Cl,--D, 0.027 f complex in HzO; E, made basic (PH obvious how this occurs. Spectra of OxaIato Complexes.-Figure 3 gives a -10); F, 2 niin. later; (c) I(NHa)6Cr-OH-Cr(NH3)6]Cl& --G, -0.017 f complex in -0.05 f HCl; H, made basic comparison between the absorption spectrum of the (PH -9; a small absorption peak a t 700 mp is only partly new compound ox(ibn)Cr-ox-Cr(ibn)ox (curve A) and that of the previously known [Cr(en)20x][Crshown); I, 2 lir. later. (en)(ox)z] (curve B) in aqueous solution. The ammonia ligands by a hydroxyl group. For all absorption peaks of the former are shifted toward three binuclear complexes the spectra of the blue longer wave lengths, in agreement with our finding “basic” cations are given in Fig. 2 (curves B, E, H), that ibn is a poorer complexing agent than en. together with spectra of the original (“acidic”) and The spectra of the separated Cr(en)zox+ and Crfinal cations. The change from “acidic” to final (en)(ox)z- ions are also given (curves C, D). cations (curves A, D, G to curves C, F, I, respec- No additional peaks were found in the range 600tively) is characterized in each case by an increase SO0 mp for any of the above species, showing that no in molar absorbancy index of the shorter wave significant amount of the original Cr(0x)3-~ was length peak relative to that of the longer wave left in the preparations. length peak; there is also a slight shift in the specExperimental trum toward longer wavelengths except for the ibn 2-Methyl-l,2-propanediamine.-Several 10-g. lots of this complex, for which the shift is negligible apparently diamine were prepared by reduction of acetone cyanohydrin because of the weaker complexing of ibn. with lithium aluminum hydride in anhydrous ether.23j28*2g The spectral peculiarities exhibited in Fig. 2 dur- The yield was only 10-15~o. Most of the diamine was ing the above reactions in weakly basic solution are donated by Commercial Solvents Corporation, New York. interesting. Like the blue basic rhodo ion, the Drying with sodium for two days, and then distillation over sodium, gave the anhydrous diamine. The product was blue species formed immediately from the tetrakis- collected t 47-48‘ (17 mm.); this boiling point is in good (ibn)-p-dihydruxo ion shows a splitting of the ab- agreementa with previously reported values. sorption bands; according to the crystal-field theAnhydrous Chromium(II1) Chloride.-Comrnercial anhyory,26 such splitting implies an increased asymme- drous chromium(II1) chloride (Fisher Scientific Company, try of the complex ion. The splitting shown in Fig. St. Louis, Mo.) was found to contain a reducing impurity 2 is greatest for the basic rhodo ion (curve H), less (27) S. E. Rasmussen and J. Bjerrum, Acto C h e w . Scond.. 9, 735 for the ibn complex (curve B) and apparently dis- (1955), have studied spectrophotometrically t h e hydrolysis of the correappeared for the en complex (curve E), behavior sponding [(en)aCo-(OH)n-Co(en)nl+4ion in basic solution; no interspectral peculiarities were reported, although t h e spectra of related to the increasingly greater rates of the sub- mediate t h e cobalt system otherwise closely resembles t h e chromium analog. sequent reactions affecting the blue cations. (To (28) H . Reihlen, G . Hessling. W. Huhn and E. Weinbrenner, An71.. (2(1) E R , W. hloffitt and C. T. Ballhausen. Awn. Rev. P h y s . Cheni.. 7 , 1 0 7 ClOX).
493, 20 ( 1 9 3 2 ) .
(29) 2. Welvart, C o ~ n p r r. e w i . , 238, 25% (1954).
June 5 , 1059
SPECTRA OF S O M E CHROMIUM(1II) %hIETHYL-1,2-PROPANEDIllMINE
which caused the formation of oily products in the reaction with ibn. One liter of 10% aqueous potassium dichromate was added t o 100 g. of the impure chloride, several ml. of concd. hydrochloric acid added and the mixture brought t o a gentle boil with constant stirring for 10 min. The separated solid was washed by boiling with successive l-liter portions of distilled water until the wash water gave a negative test for chloride ion. The solid was filtered o f f and dried a t 110'; yield -100%. The purified product showed no reaction with water or hydrochloric acid even after 3 weeks a t 25" or 3 hr. a t boiling temperature. Diaquotetrakis-(ibn)-p-oxodichromium(II1) Sulfate 7Hydrate.-C.P. hydrated chromium(II1) sulfate was finely ground, dehydrated by slowly heating t o 100" and keeping it a t that temperature for 4 days, then grinding the spongy product. With dried ibn there was no evidence of reactiov in 2 hr. a t -25", but with excess ibn (3 ibn:l Cr) a t 100 the mixture became violet within 1 hr. After 3 hr. the mixture was cooled to -25" and extracted with 1: 1 ether-ethanol t o give a violet solution which left an oily residue on evap1 with hyoration. Acidification of the extract to PH drochloric acid and addition of more ether gave a violet o f f , washed with ethanol and ether, solid, which mas fi!tered then dried over concd. sulfuric acid; yield 5 1 0 % (much unreacted chromium( 111) sulfate left in reaction mixture). Anal. Calcd. for [H20(ibn)2Cr-O-Cr(ibn)~H20] (S04)~. 7H20: C, 19.40; H , 8.50; ignition residue (CrzO(SO4)2), 31 6. Found: C, 19.39; H , 7.36; ignition residue, 30.22. The crystals dissolved readily in water. The solution turns from violet t o a red-violet on acidification with hydrochloric acid; upon making basic with sodium hydroxide the color returns t o violet, slowly becoming green. Prolonged boiling with hydrochloric acid in an attempt t o break up the bridge structure gave a green glassy solid which turned deep violet on heating. Tetrakis-(ibn)-p-dihydroxodichromium(II1) Chloride.Purified anhydrous chromium(II1) chloride showed no evidence of reaction with dried ibn within 2 hr. a t -25', but a t 100' a violet substance formed which was insoluble in the ibn. Reaction seemed to stop in 3-4 hr., apparently because the chromium( 111) chloride became coated with product; unreacted chloride was still present after 4 weeks of heating with excess ibn a t 110" in a sealed tube. Extraction of the reaction mixture with small amounts of water gave a violet solution from which a violet solid separated on addition of concd. hydrochloric acid. The solid was filtered o f f ,washed with ethanol and ether, then sucked dry; yield usually
