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52 1
A n a l . Found: N, 5.411. The n.m.r. spectrum (100 Mc./sec., CDCl, solution) clearly points to structure I b ; it consists of two symmetrical 1-proton triplets a t (13) National Science Foundation Postdoctoral Fellow 15.25 and 14.85 r ( J = 13.5 c.P.s.) assigned to the RONALD G. LAWLER'S DEPARTMENT OF CHEMISTRY H3 protons, a 3-proton multiplet a t 1.30 7 asinner JAMES R. BOLTON COLUMBIA UNIVERSITY NEW YORK27, NEWYORK GEORGE K . FRAENKEL signed to HI, a 3-proton multiplet a t 0.33 r due to H 2 , UNIONCARBIDE RESEARCH INSTITUTE THOMAS H. BROWN and a 1-proton doublet a t -0.43 T ( J = 13.4 c.P.s.) due to H2' (the proton adjacent to the substituent). UNIONCARBIDE CORPORATIOX NEW YORK TARRYTOWN, Sulfonation of Ia with oleum in dioxane a t room RECEIVED DECEMBER 21, 1963 temperature gave a water-soluble sulfonic acid (Azp-,"," 314, 440, and 590 mp), which was converted to t h e silver salt with aqueous silver nitrate and then methylElectrophilic Substitution of Aromatic Fourteenated with methyl iodide. The resulting monomethyl Membered Ring Cyclic Conjugated Systems' sulfonate (IC),formed in ca. 30% yield, crystallized as red needles, m.p. 168-169' dec. [A~,O?'a"' 315, 442, and Sir : 591 mp ( E 179,000, 20,400, and 7700); 321, 1,8-Bisdehydro [14]annulene (Ia)2-4 and monode448, and 591 mp; Anal. Found: C, 66.80; H, 4.731. hydro[14]annulene (I1 or III)2Jhave been shown to be The n.m.r. spectrum (100 Mc./sec., CDC13 solution). aromatic compounds, since they sustain an induced consists of two incompletely resolved symmetrical 1ring current as demonstrated by nuclear magnetic proton triplets at 14.95 and 14.71 T ( J = 13.2 c.P.s.) resonance (n.m.r.) ~ p e c t r o s c o p y . ~On , ~ the other hand, [14]annulene (IV)2 on this basis is n o n a r ~ m a t i c . ~ . ~due to the inner H 3 protons, a 3-proton singlet a t 5.99 T due to the methyl hydrogens, a 3-proton multiplet a t Aromatic character has usually been associated with the 1.33 T assigned to Hi, a 3-proton multiplet a t 0.25 T ability to undergo electrophilic substitution reactions assigned to H2, and a 1-proton doublet a t -0.11 T (although this need not necessarily be true for all aro( J = 13.4c.P.s.) due to H2'. matic We now report that the two aroAcylation of Ia with acetic anhydride and boron matic dehydroannulenes Ia and I1 (or 111) in fact do untrifluoride etherate in methylene chloride a t room dergo such substitution reactions, whereas the nonarotemperature gave an acetyl compound in low yield, matic [14]annulene (IV) under analogous conditions to which structure Id is tentatively assigned by analogy; does not. '321, 451, and 608 mp it formed brown crystals ;:A:[ H' (relative intensities, ca. 20 : 3 : 1) ; 2,4-dinitrophenylhydrazone:' "": :A: 505 and 619 mp]. The amount of material was insufficient for further investigation, Another acetyl compound with unusual ultraviolet properties was also formed, as will be described in a H / H H \ H later publication. Monodehydro [14]annulene (I1 or 111) on nitration H \ A H under the above-mentioned conditions gave ca. 20% of a mononitro compound as dark brown needles, H H lo , R=H IC ,R=S03Me 328 and 425 mp ( E 59,500 m.p. 185-186' dec. [A:oXCtane I t d , R=COMe b , RzN02 and 8300) ; 335 and 435 mp; Anal. Found : N , 6.671. The n.m.r. spectrum (56.4 Mc./sec., CDCI3 solution) consists of two double doublets a t 10.61 and H H 10.72 T assigned to the two inner protons, as well as a H H complex band in the 2.67-0.91 T region due to the outer protons. Nitration must have resulted in substitution of one of the outer protons, but the exact point of attack has not been determined. Sulfonation of monodehydro [ 14lannulene and subse quent methylation, as above, gave a ca. 4 : 1 mixture of two isomeric monomethyl sulfonates as dark red plates, m.p. 153-154' [ A ~ ~ ? t a n e314, 367, and 400 mp ( E 74,500, H H 6000, and 5300); Akz!ene321, 371, and 406 mp; A n a l , m Found: C, 65.32; H, 4.991. That this was in fact Ip a mixture was shown by thin layer chromatography l&Bisdehydro [14]annulene (la) underwent substi(two spots of very similar polarity) and by the fact tution at the position adjacent to the acetylene. Nitrathat the methyl proton signals in the n.m.r. spectrum tion with cupric nitrate in acetic anhydride a t room (60 Mc./sec., CDC13 solution) appeared as two distinct temperature yielded ca. 25% of mononitro compound peaks a t 6.12 and 5.91 T . Acylation of monodehydroI b as black needles, which decomposed above 200' on [14]annulene with acetic anhydride, as above, led in heating [A2,0Yne327, 467, and 605 mp (E 85,500, low yield to an acetyl derivative 329 and 420 mp 337, 476, and 608 mp; 19,000, and 7800); (relative intensities, ca. 7.5 : 1) 1. (1) This is Part X X X I in the series "Unsaturated Macrocyclic Com[ 14JAnnulene (IV) on attempted nitration, sulfonapounds"; for Part X X X , see F. Sondheimer, Pure A p p l . C h e m . , 7 , 363 tion, and acylation under the conditions used with the (1963). (2) F Sondheimer and Y Gaoni, J . A m . Chem. SOC.,81,5765 (1960). dehydro compounds gave no comparable substitution (3) F. Sondheimer, Y. Gaoni, L M. Jackman, N . A . Bailey, and R products. In no case did we observe the formation of a Mason, i b i d . , 84, 4595 (1962) substance with a higher wave length maximum in the (4) N . A Bailey and R . Mason, Proc. Chem Soc., 180 (1963). ultraviolet than the starting material, and decomposi(5) L M Jackman, F . Sondheimer, Y . ilmiel, D A Ben-Efraim, Y . Gaoni, R . Wolovsky, and A . A. Bothner-By, J . A m , Chem. Soc., 84, 4307 tion of the latter usually resulted. (1962). 1&Bisdehydro [14 lannulene (Ia) was found to form (6) J. Bregman, Nature, 194, 679 (1962) 1: 1 n-complexes with compounds such as 1,3,5-trinitro(7) F . Sondheimer, R . Wolovsky, and Y Amiel, J . A m . Chem SOL.,84, benzene ; the complex with the latter crystallized as 274 (1962) Acknowledgment.-We wish to thank Prof. Martin Karplus for many helpful discussions.
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dark red needles, m.p. 222-223' dec. (Anal. Found: N , 11.19). Similarly monodehydro [14]annulene (I1 or 111) with 1,3,5-trinitrobenzenegave a 1: 1 adduct as long red needles, m.p. 182-183' dec. (Anal. Found: C, 6 1.66, H, 3.80 ; N, 11 20). KOcomparable complex could be obtained from [14]annulene (IV). The reaction of the 14-membered ring conjugated compounds with maleic anhydride also appears to be related to their aromatic nature. Thus, 1,8-bisdehydro [13]annulene on treatment with an excess of the anhydride in boiling benzene for 1 hr. was completely unchanged, monodehydro [ 14lannulene under these conditions was recovered to the extent of 85YG,while less than 10% of the nonaromatic [14]annulene was unaffected. Acknowledgment.--We are indebted to Dr. A. Melera, Varian A. G., Zurich, Switzerland, for determining the 100 Mc./sec. n.m.r. spectra.
TABLE I HYPERFINECOUPLISCCONSTANTS A , gauss
Cr63 ?;I4
C,'3 C,'3
18.39 f 0.05 5 27 f 0 . 0 5 12 64 i 0 2 880fO3
substitution. A summary of our coupling constants is given in Table I. In the temperature range 60-100', the exchange with CI3h'- can be observed without decomposition of the complex. We have followed the decrease in the signal due to unsubstituted complex and the increase in the signal resulting from equatorial C13 substitution while the samples were held a t constant temperature in the microwave cavity of a p.m.r. spectrometer. In solutions ranging from 0.015 to 0.035 F i n complex and 0.10.2 F i n NaCN (55yGin C13 isotope), we followed the DANIELSIEFFRESEARCH INSTITUTE YEHIELGAOSI adjacent lines for unsubstituted and C13 equatorialWEIZMAXN INSTITUTE O F SCIENCE FRANZSOXDHEIMER substituted complex for the Crj3 species until approxiREHOVOTH, ISRAEL mately 50% of the complex was substituted with one RECEIVED OCTOBER 28, 1963 C13N-. These experiments were conducted in the nearly complete darkness of the cavity. In separate The Hypefine Coupling Constants and Rates of experiments no pronounced light catalysis, as reported for other cyanide complexes,' was obspved. Exchange for C 3N- with the Axial and Equatorial These exchange data were fit by rate laws assuming Positions in Cr(CN)5NO-3 first order in unsubstituted complex and zero order in Sir : total CN- concentration. An integrated rate law was It has been recently reported1,2that the magnetic used which took into account the possible substitution hyperfine interaction of C13 was observable in the of the axial and one of the four possible equatorial paramagnetic resonance spectrum of aqueous solutions CN-. The total rate constant k, 4k, can be directly of Cr(CN)5NO-3. It seemed probable that this obtained from the decrease in the unsubstituted cominteraction was only due to the equatorial CN-, but plex and the equatorial rate constant ke can be evaluated the possible axial coupling remained unknown. I n a by successive approximation from the growth of the preliminary report3 of the exchange with C13N- we equatorial C13signal. At i 5 O we obtain k, = 1 X were also unable to differentiate between the axial and sec.-l and k, = 7 X set.-'. Over the range of equatorial positions. We have now been able to temperatures we get AHa* = 33.5 f 4 kcal.!mole, prepare the complex, by exchange with C13 substituted ASa* = 18 f 8 e.u., AHe* = 30.5 f 4 kcal./mole, and primarily in the axial position and by synthesis with ASc* = 5 f 8 e.u. I n the solutions prepared by every cyanide substituted by CI3N-. Both the hyperadding NaCN to neutral solutions of the complex, the fine interaction and the rates of exchange of the axial ratio ka,'4k, = 4 f 2 over the full range of temperature. and equatorial positions have now been clearly resolved: The apparent large positive value for ASa* indicatess Samples of K3Cr(CN)5N0were synthesized4utilizing that the activated complex for axial exchange is a NaCN enriched to 55% in C13 isotope. The largest protonated species. The formation of HCr(CN)Sr\;O-* hyperfine splitting in the p.m.r. spectrum of Cr(CN)6by the removal of the proton from HCN could conNOp3 should arise from the species containing5 CrS3, tribute about 40 e.u. to the apparent entropy of activaN14, and five Cl3. In the X-band spectrum of the tion. When exchange experiments are conducted enriched sample, clearly resolved lines occur 62.4 in acidified solutions so that both CN- and HCN have gauss above and below the center of the spectrum. nearly equal concentrations, the axial rate is accelerated. Since these lines must be due to a combination of axial In this case, as previously mentioned, a line due to and equatorial C13 hyperfine interaction, this splitting axial substitution becomes prominent before the can be combined with the previously Crj3, equatorial line is clearly observable. I t seems probable N L 4 and , C13 equatorial splittings to yield a value of that the formal charge of +l on the NO group makes 8.55 f 0.4gauss for the axial CI3 coupling constant. the axial CN- more likely for protonation than the more h prominent hyperfine line can also be observed adjacent equatorial CN-. It is possible from our data, between the CI2 and the expected equatorial C13 lines however, that the equatorial exchange is also partly when the complex is exchanged in solutions containing acid-catalyzed. nearly equal amounts of C13 enriched CN- and HCN. The similar values for the N14 and both C13 coupling Direct measurement of this line gives 8.93 f 0.2 constants do not give any clear contradiction or support gauss for the axial C13 coupling constant. Our values to the bonding scheme proposedg for these complexes. can be compared to the 8.43 f 0.2 gauss reported by The axial CN- is more labile to exchange in aqueous Kuska and Rogers6 from a resolution of the complex solution primarily because of greater protonation a t this pattern observed for both axial and equatorial C13 position, and the enthalpies of activation are equally large for both positions. The theory for the isotropic ( I ) K . G Hayes, J Chem. P h y s , 38, 2.580 (1963) ( 2 ) I Bernal and S . E. Harrison, ibid.,38, 2.581 (1963). hyperfine interaction in these compounds is necessarily (3) J B Spencer and R . J Myers, presented before the Inorganic Division complex, and both the signs of the coupling constants of t h e American Chemical Society, 144th National Meeting, I,os hngeles.
+
Calif , April, 1963 (1) W P Griffith, J . I.ewis, and G Wilkinson, J Chem S O L . ,872 (1959) (.i) There is n o observable hyperfine interaction f r o m the ! i l l i n the C Y - , Cr13 is 9 .5yoa b u n d a n t (6) H. A. Kuska and M . T Rogers, we wish to thank Professor Rogers for sending us a pre-publication copy of their work.
(7) A . G MacDiarmid and N F. Hall, J A m Chem S o c , 76, 1222 (1954) (8) We wish t o thank Professor R . E Connick for suggesting this possibility t o us. (9) H B Gray, I Bernal, a n d E Billig, J . A m Chem. Soc., 84, 3404 (1962).
