pected Cop( CO)a(CaH7C=CHj? but to a mixture containing complex turned darker. After this period, tlic gas voluinc inore than two moles of alkyne per mole of Co2(CO)8. decreased a t a rate of approximately 3 nil. per hour. T h c reaction was interrupted after 26 h r . , during which tiiiic thr i l n a l . Calcd. for C O ~ ( C O ) ~ ( C ~ H ~ C = CC, H ) ~45.21; : H , 3.35. Found: C, 54.40; H, 5.30. Calcd. for Cop(C0)p crystals had turned dark red. .4n analysis of the gas showed that 0.33 mole of carbon monoxide had been evol\-ed (C~H~CSCH)~ C,: 54.73; H , 5.25. per mole of complex. From the amount of carbon monoxide The infrared spectrum of the oil differs from t h a t of Co2- evolved and the observed decrease in gas volumc, the (CO)gC3H7C=CH. The two bands located at 5.42 and amount of acetylene absorbed per mole of CO?(CO)~CHECH 3.68 are shifted to 5.33 and 5.70 and two bands a t 10.52 was found to be 1.18 moles per mole of complex. and 15.17 uresent in C O~,~ C O C Habsent in the The infrared suectrurn of the reaction Droduct dissolved .. ) ~. C S H ~ C =are spectrum of the oil. in carbon disulfid'e showed these bands (hi p ) : 4.74, 4.X2, (c) Co2(CO)&H=CH and Acetylene.-Aii erlenmeyer 4.86, 4.90, 5.30, 5.41, 5.63, 5.70, 9.15, 9.20, 10.05, 12.38, flask was charged with 1.053 g. (2.66 mmoles) of C O ~ ( C O ) ~ 13.59 and 13.79, C H s C H , the flask attached t o a gas buret and the apparatus filled with acetylene. During the first 2 hr. little if PITTSBURGH, PENSA. ~ t n ygas mas absorbed, while the bright red crystals of the NL-RRAY HILL,S.J
[CUNrKmcnuN
MUM
THE
DEPARTMEST OF CHEMISTRY, THEPENSSYLVANIA STATE L~NIVEKSITY]
Studies on Coordination Compounds. XVII. Stabilities of Bivalent Metal Complexes of Some Methylene-substituted 0-Diketonesl BY BARBARA B.AIARTIN
AND
iv. C O N A R D FERNELIUS
RECEIVEDKOVEMBER 29, 1958 Acid dissociation constants of several methylene-substituted P-diketunes and formation constants of some of their inetal derivatives have been determined. The acidity of the 0-diketones and the stability of their metal chelates appear to depend upon the type of substitution and, in the case of cyclic compounds, upon the type of ring system present.
Introduction *llthough the dissociation constants of a number of' P-diketones have been determined as well as the formation constants of a variety of metal derivatives, the literature contains only one reference to such measurements for a B-diketone with a substituent on the methylene carbon atom.2 I n this case the effect of the substituent was to lower both the acidity and the stability of the copper chelate, relative t o that of the unsubstituted compound. The present study was undertaken t o obtain more data concerning stabilities of metal chelates oi substituted P-diketones and to determine whether such substitution always lowers the stability. Previously no formation constant data concerning $-diketones in which one of the carbonyl groups is contained in a ring (a-acylcyclanones) have been reported. I n the present communication, acid dissociation constants of methylene-substituted P-diketones and a-acylcyclanones and formation constants of some of their metal chelates are reported. Results of infrared and ultraviolet spectral studies are presented Experimental 3-Diketones.- - 1 . 'Tlic prcparxtioii r i i 3-z-butyl-2,4-penI ) . p . 98-102' tanedione is tlcscrilml iii aiiotlicr pithlicatio~i~; (I!! 17 i i i i i i . ) , reported' b.p. OO-O1° (10 I I I ~ I . ) . -. 3-Allyl-2,4-pentanedionewas prepnrcd 11y tlic Iiri 1~ V ( I L I I K of English5; b.p. 88--90° (21 t i m i . j, reported5 b.p. 82-8.?' (16 IIlITI.). -
~
( I ) Abstractcd frurii a t l i ~ b i s presented lly Barbara D. l l a r t i n in partial fulfillment of t h e requirements for t h e degree of Master of : k i p t i c ? , J a n u a r y , 1959. ( 2 ) 11. Calt-in arid 1;.It'. W i l s , n , ' L H I S J o I ' K h A r . , 6 7 , 2 0 0 . ; ( l ! l l , ; ) (:i) I) F. l I a r t i n , R I . Shamma ant1 \T C . l'erneliuq. ihici.. t r ~be (>ubIislied. ( I ) I I ~ l d k i i i s ,\T, ILiiriz a n d D. 1) Coilm;iii, i h i i i . , 6 6 , l32l2 I l $ l : ! ~ l l (.7) I. P.Rngli*li, r I 1 1 1 , ihiii., 6 8 , 4.73 (1QtI't).
3 . Dibenzoylmethyl bromide was prepared by tlic method of de Seufville and von Pechmanne; m.p. 91-92", reported6 m.p. 93". 4. 2-Acetylcyclohexanone was prepared by the metliod of Hauser, et al.'; b.p. 103-109' (17-18 mm.), reported7 b.p. 110-115° (20 mm.j. 5. 2-Benzoylcyclohexanone was prepared by the method of Hauser, et aZ.8; m.p. 85-87', reported8 m.p. 88-89'. 6. 2-Benzoylhydrindone was prepared by the method of Hauser, et ai.*;m.p. 98.8-100", reporteds m.p. 10O-10lo. 7 . 2-Acetylcyclopentanone was generously supplied by the hmerican Petroleum Institute Project 42. T h e titrations were preformed as previously described , 9 Acid dissociation constants were determined according to the method of T'an Uitert.'O Calculations were made by the method of Block and McIntyre." Infrared absorption spectra were obtained with a PerkinElmer model 21 Double Beam Recording Spectrophotometer using a sodium chloride prism. The spectra of liquid samples were obtained as thin liquid films pressed between plates of sodium chloride, and those of solid samples were obtained in disks of potassium bromide. Ultraviolet absorption spectra were obtained with a Warren Spectracord having a hydrogen lamp light source and using 2-cm. quartz cells. Samples were prepared by dilution of stock solutions which contained from 7 to 15 mg. of material per 100 ml. of redistilled 95% ethanol.
Results and Discussion The plots of the pKn values for the P-diketones studied as a fuiiction of inole fraction of dioxane a t 30" were linear. Table I gives mathematical expressions for the curves which fit the mathematical data within +0.05. The formation co11stants (log K for the reactions AI++ Ch- ?i
+
(0) R. de Seufville and H . \ a n I'echmann, B e y , , 23, 3375 (1890) (7) R. Lexine, J . A . Cunrr,y, J . 1'. Ariams and '2. R. Hauser, THIS 6 7 , 1510 (1916). 18) C . K. H a u s e r , B. I. Ringler, 1, \\-, Swamcr ani1 1 ) 1'. l h r t t n l w m ,
JOURNAL,
I) I , G .
1 0 ) (a) I,
\'an Uitert, ( A ; , , {bid., 7 6 , 131, 1.57 (1933), C . Tali I-itert. rl n l , thiil., 7 6 , 4,i: f I 9 5 3 ) ; (b) 7 6 , 5887
, l!I.j&), ' I 1 1 I ( I'
I1-2,4-pentanedione Dibenzoylmethl 1 bromide 2--hcet>lcyclopeiitaai me L'-Benzo>lhydrindonc 2-.icetylc>clohcvanone 2-Benzol lcyclohexanonc a vs weak.
=
very strung,
b
=
b
I t is interesting to note whether a correlation can be found between enol content and acidity. X rough indication of enol content of P-diketones can (1 1) I,. J. Rellamy, "The Infrared Spectra of Complex Rlulecules," ?nil liil , AIethuen. 1.ond011, l ! i 5 8 , 1). 12:3
234'1
Vd. s1
N. C. DEXU,H.E. BERKHEIMER, If-. L. EVANS A N D €1. J. PETERSON
be obtained from the ratio of the intensity of the band attributed to the free carbonyl group to that of the band attributed t o the enol-chelate structure. I n 2-benzoylhydrindone this ratio is roughly 0.1 : l ; 2-benzoylcyclohexanone, 4 :1; 2-acetylcyclohexanone, 0.4:l; 2-acetylcyclopentanone, 1:l. -4pparently, in the compounds just mentioned no correlation exists. For example, 2-benzoylhydrindone is a stronger acid than 2-benzoylcyclohexanone but appears to have the lower enol content of the two compounds. On the other hand, 2-acetylcyclohexanone is the stronger acid and has a higher enol content than 2-benzoylcyclohexanone. The strongest acid of the /?-diketones studied, i.c., 3-acetylcyclopentanone, has a lower enol content than does 2-acetylcyclohexanone. Among the straight-chain p-diketones in this study, a correlation appears to exist. The intensity ratios of these conipounds are: dibenzoylmethyl bromide, 1.58:1; 3-allyl-2,4-pentanedione, 1 . 7 7 : l ; 3-n-butyl-2,4-pentanedione, 2.17:l. Dibenzoylniethyl bromide, the strongest acid, has the highest enol content; 3-n-butyl-2,4-pentanedione, the weakest acid, has the lowest enol content. The ultraviolet absorption maxima of interest for the /3-diketones studied are listed in Table IV. I t will be seen from the table that, for these 8diketones, the logarithm of the extinction coefficient of a given peak remains essentially constant as the concentration is changed. This adherence to Beer's law usually is observed among /3-diketones
TABLE IV LTLTRAVIOLET r\I3SORPTION SPECTRAL DATA O F Molarity X 106
B-Diketonc
mp
291 291 3-Allyl-2,4-pcntancdione 288 288 Dibenzoylincthyl broniide 232 235 2-.~cetylcyclopentaiioiic 289 289 289 2-Bcnzoylh~clrii1tloiie 249 249 355 2-~lcctylcyclo~lcxanonc 11.3 290 5.64 290 ~ - B c I ~ z I I ~ ~ ~ ~ ~ I ~ ,5.05 I ~ ~ ~315 ~ ~ 249 11.0 315 3-n-But?-l-2,4-pcntane~ionc
4 88 9.75 18.7 9.35 4.23 1.69 6.26 5.01 3.50 4.62 0.965
P - IjIKETOXES I
loF: amax
3.42 3.40 3.56 3.59 4.21 4.17 3.91 0.77 3.89 0.37 3.87 1.30 4.15 0.27 4 . 1 5 0.46 4.38 2.01 3.95 0.808 3.80 0.58 I ~ I ) I3~. 7c1 1 . 1 2 4.01 1.04 3.68 0.258 0.418 1.34 0.72 1.39 0.50 1.02
and is interpreted to mean that the ratio of keto t o enol forms is not changed with concentration. Acknowledgments.-The authors gratefully acknowledge the support of the United States Air Force, Contract AF 33(616)-2742, and the United States Atomic Energy Commission, Contract AT(30-$907. UNIVERSITYPARK, PESNA.
[CONTRIBUTIOX FROXI THE C O L L E G E O F CHEMISTRY A S D PIIYSICS, THE PENNSYLVANIA S'rATE UNIVERSITY]
Carbonium Ions. VII. An Evaluation of the H , Acidity Function in Aqueous Perchloric and Nitric Acids',' BY N. C . DENO,HENRYE. BERKNEIIIER, WT;ILLI.\ni L. EVANS AND HEXRYJ . PETERSON RECEIVED SOVEMBER
21, 19j8
The I ~ acidity R function (previously termed CQand J o as well as H R ) has been evaluated for 0-6070 perchloric acid and O-5F3yo nitric acid. Values of p K n + log (CROH/ICR+) are equal when determined in different aqueous mineral acids; and values of d log ( c R o R / c R + ) , ' ~ 70acid are independent of the structure of R. T h e symbol c refers to the concentration in moles/l. These two facts demonstrate t h a t a class nf cation exists, the arylmethyl cations, for which the values of the activity coefficient (In+) are equal in aqueous mineral acids. The structural characteristics of this class are discussed in light of solubility measurements on perchlorate salts in aqueous sulfuric acid. The equilibrium between HNOl and N O + follows the HR function in aqueous perchloric acid.
+
Evaluation of HRin Perchloric and Nitric Acids. -The HR acidity function previously had been evaluated in O-9iyo sulfuric acid using eq. 1 and a series of arylmethanols as indicator^.^ It has now (1) This research was supported in p a r t b y a g r a n t f r o m t h e Petroleum Research F u n d administered by t h e American Chemical Society. Grateful acknowledgment is hereby m a d e t o t h e donors of this fund. T h i s research also was supported in p a r t by a g r a n t f r o m t h e S a t i o n a l Science Foundation. Grnteful acknowledgment is hereby made nf this support. ( 2 ) T h e acidity function defined as equal t o PKR+ log ( c n o H / r R + ) has been known as (70in our publications. . i n in publications b y V. Gold a n d co-workers, a n d I I R in publication.: by C. Williaiiis ant1 CIIworkers. T h e symbol €I11 seems preferable since i t intiictiles t h e cluse relationship t o t h e Ho acidity function. This f a c t coupled with its priority ( A . hl. Lowen, >I. A. M u r r a y a n d G. Williams. J . Cheriz. SOC., 3321 (1950)) has led ns t o abandon t h e symbol Co ( a n d Jo) and t o use HI
