4862
COMMUNICATIOXS
MOLECULAR STRUCTURE OF C8H8Fe(CO), I - ----
Sir :
There have been a number of suggestion^^^"^^^^^^^ that the cyclooctatetraene (COT) ring in CsHsFe(C0)s is planar, and one suggestion7 that the tub form, like that established for free cycloiictatetraenesvYt10 and its silver complex, i i , 1 2 occurs in this compound. A similarly large number and greater variety of suggestions for the geometry of the CgHs ring in (OC)3FeCsHsFe(C0)3were shown to be incorrect, when the unsuspected chair form was proved.13 We show here that yet another geometry, a dihedral form not included in any of the above predictions, occurs for the cycloiictatetraene ring in CsHsFe(C0)3.
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FRACTION.
Fig. 1 --,lbsorbancies (A) a t 260 m,u of fractions obtained by chromatography of pancreatic ribonuclease digests of 1.5 tng. each of the purified alanine-acceptor RXA (bottom
curve), valine-acceptor KX.4 (middle curve), and tyrosineacceptor RXA (top curve) on DEAE-Sephadex. (The column, 0 25 X 50cm., was eluted with an increasing gradient of ammonium carbonate produced by using 120 ml. of water, 120 ml. of water, and 116 ml of 0 . i 5 Mammonium carbonate respectively, in three chambers of a T‘arigrad (see ref 4). The volume of the fractions was 2 2 ml )
fraction 90, very pronounced in the digest of the alanine RNA, is believed to be GpUp, the last of the dinucleotides to be eluted. Comparison of the three curves in Fig. 1 indicates that there is hardly a single oligonucleotide that occurs to the same extent in any two of the RNAs. The chromatographic analyses on DEAESephadex are highly reproducible and even the smaller differences in the curves are believed to be real. It is clear that the alanine-, valine-, and tyrosineacceptor “solubleJ’ R N , k of yeast differ greatly in structure. The differences between these three RNAs are much more complex than would be required by simple hypotheses of information transfer by nucleic acids. Acknowledgment.-This work was supported in part by grants from the National Science Foundation and the National Institutes of Health.
Fig. 1.-The structure of CsH8Fe(C0)3: bond distances are C1-Ce = C3-C4 = 1.42, C2-C3 = 1.42, C4-Cj = C1-Cx = 1.45, C6-G = c7-C~ = 1.34, C&7 = 1.49, Fe-C1 = Fe-C4 = 2.18, Fe-CZ = Fe-Cz = 2.03, Fe-C (carbonyl) = 1.80 (av.), C-0 = 1.13 (av.) all S about 0.02 A. Bond angles are C1-C2-C3 = C2-C3-C1 = 124.6’, C3-C4-Cj = CBCl-Cs z= 132.4’, C~-CSCB = Ci-Cs-C7 = 133.2, CB-CG-C, = Cs-CrC6 = 131.8’, all i :about l o ,and t o be compared with 135” in the regular plane octagon. The angle betiyeen normals t o the two planes in CsHs is 41’ in CSH8Fe(C03).
A total of 856 observed X-ray diffraction maxima from a single crystal of symmetry Pnam with four molecules in a unit cell of dimensions a = 6.54, b = 13.46 and c = 11.51 A. has yielded an agreeZ~Fo~ ment factor of R = ZIIFol - ~ ~ c ~ ~ , ’ = 0.091. The molecular structure (Fig. 1) shows that the Fe(C0)3 group is attached to a “buta(1) T.A. Manuel and F. G. A. Stone, Proc. Chem. Sac. ( L o n d o n ) , 90 (1959). (2) T. A. Manuel and F. G. A . Stone, J . Am. Chenz. SOL.,62, 33G (1960). (3) D. A. Brown, J . Inorg. aild fluclear Chem., 10, 3 9 (1959); 10, 49 (1959). (4) F. A. Cotton, J . Chem. SOC.( L o s d o n ) , 400 (1960). (5) P. L. Pauson, Proc. Chem. SOC.(London), 297 (1960). ( 6 ) L. E. Orgel, “ A n Introduction to Transition Metal Chemistry: Ligand Field Theory,” John Wiley and Sons, S e w York, N. Y., 1960, p. 159. (7) A. Nakamura and N. Hagihara, Bull. Chem. Soc. J a p a n , 32, 880 (1960). (8) H. S. Kaufman, H. Mark and 1. Fankuchen, Naluue, 161, 165 (1948). (9) J. Bregman, private communication. (10) 0. Bastiansen, L. Hedberg and K. Hedberg, J . Chem. Phys., 27, 1311 (1957). (11) F. S. Mathews and W. h’. Lipscomb, J . Am. Chern. SOC.,60, 4745 (1958). ( 1 2 ) F. S. Mathews and W. X. Lipscomb, J . Phys. Chem., 63, 848 (1959). (13) B. Dickono and W. N. Lipffiomb, J . A m . Chem. Soc., 83, 489
U. S PLANT, SOILA N D NUTRITIOK LABORATORY, SWCRD, 4RS,U S DEPARTMENT OF AGRICULTURE, A N D DEPARTMENT O F BIOCHEMISTRYROBERT w. HOLLEY JEAN APGAR C O R N E L L U N I V E R S I T Y , ITHACA, s.Y . SUSANH. MERRILL PAULL.ZUBKOFR RSWrv8a PiavsMssR 8 , 1961 (1961),
Dec. 5 , 1961
COMNUNICATIONS TO THE EDITOR
4SG3
diene" part of the CsHs ring in a structural unit hexaenediyne (bis-dehydro [ 16]annulene2). These 16 a-electron systems were expected to be nonwhich is proving increasingly neaily genera1,'~4~15,16.17 aromatic, since they do not comply with Hiickel's and which was suggestedls for C&Fe(C0)3, 2) nand employed19 in interpreting closely related rule for aromaticity [presence of (4n compounds and associated reactions. The struc- electrons]. Reaction of trans-l,4-dibromo-2-butene with ah ture also shows that six of the eight atoms of the ring are very nearly coplanar, and that six of the excess of ethynylmagnesium bromide in tetraeight bond angles of the ring are within about 3' hydrofuran in the presence of cuprous chloride of the 135" angle of a completely regular and yielded besides other products3 ca. 25% of trans-4planar ring. The nature and extent of these dis- octene-1,7-diyne (I) [m.p. 15", b.p. 59-60' (25 tortions from the tub form of uncomplexed cyclo- mm.), n l 9 ~1.4718; CsHs (found: C, 92.28; H, octatetraene make i t possible that the (COT)- 7.80; act. H, 2.01); no high-intensity absorption and (COT)-2 ions may achieve planarity without HC=CCH~CHLCHCH~C~CH great difficulty, as has long been anticipated I from molecular orbital theory, and recently proV posed20s21 in connection with the preparation and properties of these ions, but distortions from planarity cannot yet be ruled out. Aside from r=-=rs?---these large bond angle distortions, the distances in the uncomplexed half of the ring in CsHsFe(CO): are very suggestive of a butadiene residue, but a comparison of overlap integralsz2which are 0.25 between C4-C6 or c 1 - C ~ in CsHsFe(C0)3 and 0.04 between corresponding atoms in (0C)SFe(CsHs)Fe(C0)2, indicates that the butadiene halves of the CsHs ring interact more strongly in CsH,Fe(CO), than in (OC)3FeCsHsFe(CO)3. It is not known whether the equivalence of H1 nuclear magnetic resonances, previously incorrectly attributed13 to (OC)sFeCsHsFe(CO)a, observed1j2for CsHsFe(C0)3is indicative of negligible relative chemical shifts, a dynamical effect, or some difference of molecular geometry upon solution in carbon disulfide. A study of the temperature dependence of this spectrum may be of some help in elucidating this problem. We wish to thank Dr. T . A. Manuel and Dr. F. G. A. Stone for their courtesy in supplying us VI1 VI11 with a sample, and we acknowledge support of this research by the Office of Naval Research. in the ultraviolet]. Coupling of I by passing oxygen into a mixture containing this hydrocarbon, (14) 0. S. Mills and G. Robinson, PYOC. Chem. SOC. (London), 421 (1960). ammonium chloride, cuprous chloride, ethanol and (15) A. A. Hock and 0. S. Mills, Acta C r y s f . ,14, 139 (1961). dilute hydrochloric acid4 a t 55" for 80 minutes (16) L. F. Dah1 and D. L. Smith, private communication, 1961. produced ca. 25y0 of the linear dimer trans-trans(17) R. E. Dodge and V. Schomaker, private communication, 1961. 4,12-hexadecadiene-l,7,9,15-tetrayne(11) [color(18) B. F. Hallam and P. L. Pauson, J . Chem. Soc., 642 (1958). (19) R. B. Woodward, private communication, 1961. less plates, m.p. 79-80'; C16H14 (found: C, 93.29; (20) T. J. Katz, J . A m . Chem. Soc., 82, 3784, 3785 (1960). H, 6.79); 225, 239 and 253 mp ( E 430, (21) T. J. Katz and H. L. Straws, J . Chem. P h y s . , 32, 1873 (1960). 390 and 240); converted by full hydrogenation (22) R. S. Mulliken. C. A . Rieke, D. Orloff and H. Orloff, ibid., to n-hexadecane, m.p. and mixed m.p. 17+18°] 17, 1248 (1949). D E P A R T M E N T O F CHENISTRY BRIANDICKENS and 3 per cent. of the cyclic dimer trans-transHARVARD UNIVERSITY WILLIAMN. LIPSCOMB 1,9 - cyclohexadecadiene - 4,6,12,14 - tetrayne (111) CAMBRIDGE 38, MASS. [colorless plates decomposing explosively a t ca. RECEIVED NOVEMBER 8, 1961 215"; C16H12 (found: C, 94.44; H, 5.96); 12:;' 232, 245 and 258 mp ( E 740, 780 and 490) ; no terUNSATURATED MACROCYCLIC COMPOUNDS. XXIV.1 minal acetylene (infrared) ; converted by full hydroSYNTHESIS O F FOUR COMPLETELY CONJUGATED genation to cyclohexadecane, m.p. and mixed SIXTEEN-MEMBERED RING CYCLIC SYSTEMS m.p. 61-62']. Sir : Treatment of the cyclic dimer 111 in benzene We have synthesized four completely conju- with a saturated solution of potassium t-butoxide gated sixteen-membered ring monocyclic hydro- in t-butyl alcohol a t 40' for 1 minute yielded an carbons, namely, cyclohexadecaoctaene ( [ 16lan- isomeric mixture of bisdehydro [ 16]annulenes, nulene2), cyclohexadecaheptaenyne (monodehydro- chromatography on alumina giving violet and [16]annulene2) and two isomers of cyclohexadeca- then orange solutions with main ultraviolet maxima
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I
(1) Part XXIII, F. Sondheimer, R.Wolovsky s n d Y . Amiel, J . A m .
Chem. SOC.,in press. (2) For the nomenclature employed, see Part XXI of this Series (P. Sondheimer and R. Wolovsky, zbid., in press).
(3) See F. Sondheimer and Y Gaoni, ibid ,82,5785 (1960); 83, 1259 (1961). (4) See F. Sondheimer, el a i , &bid., 79, 5817, 6283 (1Q57), 81, 6301 (1959).
