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of a rapid equilibrium between organobornne, ole-
CHB
CI13
fin and boron-hydrogen bonds i n the thermal rearrangement reaction becomes highly reasonable. These results and others will be reported i n gi eater detail in the near future.
\
I I- - - -CII I
C H3
Vol. 8%
I1
phase chromatographical a n a l y ~ i s . ~However, after heating I at 160-175O for six hours the product obtained on oxidation was essentially pure 1,spentanediol, yield SO$&, b.p. 134-135' at 14 mm., n Z 51.4459, ~ bisphenylurethan, m.p. 171.5- 172 o,6 indicating that isomerization of I to 1,5-bis(1-boracyclohexy1)-pentane(IT)had occurred. Treatment of 1,j-hexadiene with diborane gave 1,G-bis-(1-boracycloheptyl)-hexane (111) in 82yo yield (b.p. 131-132' a t 1 mm.; Anal. Calcd. for C18H36B2:C, 78.9; H, 13.2; B, 7.9. Found: C, 78.7; H , 13.2; B, 7.5) which was converted by alkaline hydrogen peroxide to essentially pure 1,G-hexanediol, b.p. 114-11s' a t 3 mm., m.p. 41-42'. On heating 111 at 160-175" for G hours
COXTRIBUTIOS h-0.9s E. I. D C PONT D E XEMOURS ASD COMPANY, I N C . ELASTOMER CHEMICALS DEPARTMEST ~ ' I L M I N G T O K , DELAWARE KLAUSA. SAECEBARTH RECEIVED JASUART 21, 1960
I,1-DIFERROCENYLETHANE. A FRIEDEL-CRAFTS REARRANGEMENT
Sir:
1,2-Diferrocenylethane1and 1,2-diferrocenyl-l,2diphenylethane2 (the latter in nzeso and racemic form^)^^^ have been shown to be the products of the reactions of ferrocene and concentrated sulfuric acid with formaldehyde and benzaldehyde, respectively. 1,2-Diferrocenylethanehas been prepared also by the coupling of ferrocenylcarbinol in concentrated sulfuric acid,' and this method now has been extended to the preparation of 2,3diferrocenyl-2,3-dimethylbutane, m.p. 74-75 [-.I nul. Found: C, 65.47; H, 6.711, from isopropenylferrocene, m.p. i i 5 - 7 8 . 5 O [dnal. Found : C, I11 Iv 65.74;H , 6.321, Xmax 275 mp, Emax 9440. c Although the structure of 1,2-diferrocenylethane was proved by unequivocal synthesis, an apparent residual contradiction has lingered from the earlier reported preparation of a compound of this structure (reported m. p. "about 135°")5 from the reaction of ferrocene with 1,2-dichloroethane and v CH3 aluminum ~ h l o r i d e . ~ fThe point now has been resolved by the demonstration that this product is rearrangement to I V occurred as evidenced by an reality 1,l-diferrocenylethane(I). 52% yield of a 70:30 mixture (v.P.c. analysis) of in Under the conditions employed by the previous 1,5- and 1,G-hexanediols (predicted: 67: 33), b.p. workers,j a crude product isolated in the present 135-140" a t 16 mm., n Z 51.4485. ~ Hydroboration of 1,4-hexadiene gave the mixture of organoboranes study indeed melted 132-131". However, after the pure (V), which on oxidation produced a 75% yield of a chromatography or vacuum sublimation, 147-149" [.-1nal. material obtained had m.p. 13:57 mixture (v.P.c. analysis)a of 1,4- and 1,5Found: C, 66.11; H, 5.86; C-CH3, 3.511. Its hexanediol, b.p. 130-136" a t 18 mm., nZ5D1.4496. n.m.r. spectrum [T 5 3 6 (ferrocene rings), 6.58 On heating V a t 160-175O for six hours thermal ( a - H ) , 8.86 (aliphatic CH3)] was quite distinct rearrangement to I V occurred, since on oxidation from that of 1,2diferrocenylethane and was in a 76% yield of a G9:31 mixture (v.P.c. analysis; accord with the 1,l-diferrocenylethane structure. predicted 67: 33) of 1,5- and 1,6-hexanediols was The structure of the compound was corroborated ~ isolated, b.p. 139.5-142' a t 18 mm., n Z 51.4450. (1) K. L. Rinehart, Jr., C. J. Michejda and P. A. Kittle, THIS These results present excellent confirmatory evidence for the bis- (1-boracycloalkyl)-alkane struc- JOURNAL, 81, 3162 (1959). (2) K . L. Rinehart, Jr., C. J. Michejda and P. A. Kittle, X V I I t h ture for the diene-bishydroboration products' International Congress of Pure and Applied Chemistry, Munich, and indicate the thermodynamic control of the August, 1959; cf. Anpew. Chem., 72, 38 (1960). (3) h'o evidence was obtained for a n intermediate hydroxy comboracycloalkyl ring enlargement or contraction process, as would be predicted from the heats of pound ("CsHsCHOH-CioHsFe-CHCsHs-CioHsFe. m.p. 2F8-270°"), -3
combustion of the analogous cycloparaffins.' In this light Brown's suggestionzaof the existence ( 5 ) A 2.5 m. silicone rubber on Celite column operated a t 190' was used. (6) 13. Adkins and H. R . Billica, THISJOURNAL, 7 0 , 312.5 (1948); report b.p. 122-127' (7 mm.), 1 ~ 2 1,4490, 5 ~ phenylurethan, m.p. 171172'. ( 7 ) W. G. Dauben and K. S Pitzer, in M. S . h'ewman, "Steric Effects in Organic Chemistry," John Wiley and Sons, Inc., New York, N. Y.,1956, p. 4.
reportedly isolated b y Nesmeyanov and Kritskaya [Isuesl. A k a d . N a u k S . S . S . R . , Oldel. Khim. N a u k , 2 5 3 (1956)l. Since t h e mode of formation of these compounds' renders a n alcohol of this nature extremely improbable, t h e compound was presumably the higher melting diferrocenyldiphenylethane isomer in impure form. This isomer, m.p. 280281",2*' exhibits the solubility properties ascribed t o t h e "alcohol" in t h e earlier publication. (4) Cf. also A. Berger, W.E. hlcEwen and J. Kleinberg, Chem. and Znd. (London), 204 (19GO). (5) A. N . Nesmeyanov and N. S. Kochetkova. Doklady A k a d . N a u k S.S.S.R., 109, 543 (1956). (6) Although t h e compound is described in t h e original paper only a s "diferrocenylethane," t h e 1.2-diferrocenylethane structure implied is stated explicitly in subsequent papers and reviews by t h e same authors; cf., inter alia, A . N. Nesrneyanov and E. G . Perevalova, C s p e k h i Khiin., 27, 3 (10383, nnrl ref. (IO).
April 20, 1960
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by independent synthesis. Diferrocenyl ketone, THE T - T * PHOSPHORESCENCE OF CHLOROPHYLLS a AND b1 m.p. 210-21 1O,' was treated with methylmagnesium iodide and the product dehydrated to give Sir: Although the phosphorescence of chlorophyll unsym-diferrocenylethylene, m.p. 162-164' [Anal. ~,~ to photograph Found: C, 66.70; H, 5.181, Xmax 252 mp, Emax b has been ~ b t a i n e d , attempts 18,700. The olefin then was hydrogenated t o the phosphorescence spectrum of chlorophyll a authentic 1,l-diferrocenylethane,whose m.p. (144- have not been successful. Recently, Fernandez and Becker4 observed the 146") showed no depression with the dichloroethane-aluminum chloride product, and whose long-lived emission spectra of ?olutions of dJy infrared spectrum was identical to that of the chlorophylls a and b a t 7550 A. and 7330 A., respectively. On the basis of solvent studies Friedel-Crafts material. The rearrangement presumably proceeds by the concerning both the absorption and emission specpath shown, involving the very stable intermediate tra, the emissions were assigned as phosphorescences cation (II),*and is unusual in that the reaction of arising from transitions from n-T* triplet states. The present investigation employed both 3benzene with 1,2-dichloroethane is reported to proceed, without rearrangement, to give b i b e n ~ y l . ~methylpentane and ether-ethanol-hydrocarbon (EThe great stability of the cation (11) presumably PA) solvents. The 3-methylpentane was purified supplies the driving force for the different path by distillation and chromatography but not dried as by Fernandez and Becker.* The chlorophylls taken in the present study. This demonstration of the structure (I) of the a and b were crystalline, spectroscopically pure simple Friedel-Crafts product renders still more samples5 prepared and analyzed according to implausible the recently proposed'O structure (111) Stoll and WiedemannP The concentrations employed were approximately 2 X M . All for the polycondensate from the same reaction. samples were degassed and sealed in vacuo to prevent air or photooxidation. Studies were carried out a t 77°K. employing two different spectrographs and hyper-sensitized Kodak spectroscopic plates, types M, N and Q. Special attention was given to hyper-sensitization of the plates regarding temperature and ammonia concentration. That is, the temperatures of all solutions were kept a t or below 4 O and the percentage ammonia was approximately 0.5. This procedure both improves plate sensitivity and decreases background. The Fe improvement is particularly noticeable in plate CH, types hZ and Q. Light sources were either a high pressure 1 kw. Xe-Hg lamp or a 500-watt proI jection lamp. Excitation light was selected by Fe means of glass and solution filters or a grating monochromator. The emission spectrum of chlorophyll b consists I of two rather poorly resolved bands in the nearinfrared region. One band occurs a t 8750 =+= 50 A. and the other a t 9150 f 50 The locatio3 of the first band differs by approximately 100 A. from that previously reported.2 The second band is a new gne. The emission extends to approximately 9800 A. The lifetime of the emission has been determined to be 3 5 X second. The emission spectrum of chlorophyll a also I11 appears to consist of two bands but these are even less resolved than for chlorophyll b. The first (7) Prepared in 31% yield b y a n earlier method (R.B. Woodward band occurs a t 8F50 f 50 and the second band and E. Csendes, personal communication), from ferrocene, phosgene and aluminum chloride. Woodward and Csendes found m.p. 206a t 9250 50 A. The emission extends to ap2080. proximately 10,000 A. The lifetime of the emis( 8 ) J. H. Richards and E. A. Hill, THIS JOURNAL, 81,3484 (1959). sion has been determined to be 3 5 X second. (9) (a) C. A. Thomas, "Anhydrous Aluminum Chloride in Organic It has not been possible to decide whether the Chemistry," Reinhold Publ. Carp., New York, N. Y.,1941, pp. 110, 815; (b) G.S. Kolesnikov, V. V. Korshak and T. V. Smirnova, Izved. two band system represents transitions between Akad. N a u k S.S.S.R., Ofdel. Khim. N a u k , 172 (1955). different electronic states or between different (10) A. N. Nesmeyanov and N. S. Kochetkova, Doklady A k a d . N a u k vibrational states. However, the low energy s.s.s.R.,i a 6 , 3 0 7 (1959). spacing strongly indicates that the bands are vi(11) Undergraduate Research Participant, supported b y a grant ( N S F G-8521)from the National Science Foundation. brational in origin. The emission intensity of the
6&
A.
A.
(1) Supported b y the Robert A. Welch Foundation. DEPARTMEST OF CHEMISTRY AND (2) R . S. Becker and M. Kasha, THIS JOURNAL, 77.3669 (1955). CHEMICAL ENGINEERING KENNETH L. RINEHART, JR. UNIVERSITY OF ILLINOIS PAULA. K I T T L E ~ ~ (3) N. Calvin and G. Dorough, ibid., 7 0 , 699 (1948). (4) J. Fernandez and R. S. Becker, J . Chem. P h y s . , 31,467 (1959). URBANA, ILLISOIS ALAN F. ELLIS ( 5 ) Kindly provided b y Sandoz Ltd., Bade, Switzerland. RECEIVED MARCH 7, 1960 (6) A. Stoll and E. Wiedemann, Helv. Chim. A c f a , 42,679 (1959).
