COMMUNICATIONS TO THE EDITOR
Dec. 5, 1958
6459
The infrared spectrum of the trichloromethyl compound shows two C-H stretching frequencies, a t 3.25 p and 3.45 p. Similar frequencies are observed in compounds containing a cyclopentadienyl ring u bonded to a metaL3 Cyclopentadienyl rings that are n bonded are known to have only one C-H stretching frequency, in the region 3.20-3.25 The weak absorption a t 6.2 p characteristic of u bonded cyclopentadienyl rings is also present. The infrared spectrum indicates that a t least one ring in the trichloromethyl compound is u bonded to the cobalt. I n this case, the formation of the compound involves a rearrangement from n to u bonding. Other indications for u bonding are that (13) K. Shirume, A. B . Lerner and T. B. Fitzpatrick, Endocrinol., the compound reacts with maleic anhydride in 64, 553 (1954). (14) We wish to express our gratitude to Drs. A. B. Lerner and M. R. warm benzene and also reacts with ferrous chloride Wright of the Department of Medicine, Yale University School of in tetrahydrofuran to form small amounts (about Medicine, for these assays. one per cent. yield) of bis-cyclopentadienyliron(I1). KLAUSHOFMANN BIOCHEMISTRY DEPARTMENT MIRIAME. WOOLNER The other products of these reactions were not UNIVERSITY OF PITTSBURGH HARUAKI YAJIMA identified. Piper and Wilkinson2 have shown that SCHOOL OF MEDICINE GERTRUDE S P ~ H L E Rthese two reactions can be used as qualitative THOMAS A. THOMPSON PITTSBURGH, PENNSYLVANIA tests for a u bonded cyclopentadienyl group. ELEANORE T. SCHWARTZ Assuming u bonding for one ring, the reaction RECEIVED OCTOBER 10, 1958 with ethanol-water involves a second rearrangement, from u bonding back to n bonding. Herwig and Zeiss4have postulated a similar rearrangement REACTION OF BISCYCLOPENTADIENYLCOBALT(I1) WITH involving (CaHs)&r. The possibility that the triORGANIC HALIDES chloromethyl group is bonded to one of the rings sir : has been considered but discarded as incompatible Wilkinsonl has reported that bis-cyclopenta- with this reaction. dienylcobalt(I1) reacts with ethyl bromide to form Another possible explanation is the formation of bis-cyclopentadienylcobalt (111)bromide. We have a u bond between the trichloromethyl group and observed that with certain halogenated hydro- the cobalt, the rings retaining their n character, carbons, new covalent cyclopentadienylcobalt com- but sufficiently distorted by the large u bonded pounds are formed as well as the bis-cyclopenta- group to account for the infrared spectrum and dienylcobalt(II1) halides. The formation of these the chemical reactivity. This would eliminate the new compounds may involve a rearrangement from necessity for ir to u and u to n rearrangements. n bonded cyclopentadienyl rings to u bonded rings. Further work is a t present being carried out to We wish t o report some preliminary work on the establish the structure and bonding in this comreaction of bis-cyclopentadienylcobalt(I1) with pound and in the products of similar reactions with carbon tetrachloride. other organic halides. A detailed account of this On the addition of bis-cyclopentadienylcobalt(11) work will be published in the near future. to carbon tetrachloride in an inert atmosphere, bis(2) T. S. Piper and G. Wilkinson, i b i d . , 3, 104 (1956). cyclopentadienylcobalt(II1) chloride precipitates (3) T.S. Piper. F. A. Cotton and G. Wilkinson, ibid., 1, 165 (1955). (4) W. Herwig and H. H. Zeiss, THISJOURNAL, 1 9 , 0501 (1957). leaving a cyclopentadienylcobalt compound in No. 672 FROM THE INSTITUTEFOR ATOMIC solution. Removal of the carbon tetrachloride by CONTRIBUTION AND DEPARTMENT OF CHEMISTRY vacuum distillation leaves a residue which after RESEARCH LABORATORY SEYMOUR KATZ sublimation and fractional crystallization from AMES IOWASTATECOLLEGE JAMESF. WEIHER hexane has the composition (C5H&CoCCls. Calcd. AYES, IOWA ADOLFF. VOIGT RECEIVED SEPTEMBER 26, 1958 for (C5H6)2CoCC13:C, 42.96; H, 3.28; Co, 19.17; C1, 34.59. Found: C, 42.94; H, 3.46; Co, 19.34; C1, 33.04. Molecular weight calcd. : 307.5. Found: S-BIS-( 2-CHLOROETHYL)-AMINOURACIL, 315. The yields of the trichloromethyl compound A NEW ANTITUMOR AGENT and the bis-cyclopentadienylcobalt(II1) chloride Sir: are 90% and loo%, respectively, based on the Since the discovery of the pharmacological equation properties of methyl-bis-(2-chlaroethyl)-aminel 2( CrHr)iCo CClr +(C‘Hr)zCoCClr (CrHs)iCoCl HN2l and its therapeutic use in human maligThe trichloromethyl compound, m.p. 79-80’, nancies,l a number of analogs and related alkylatis orange to red depending on crystal size, de- ing agents have been developed which have clinical composes over a period of hours above 40°, and is va1ue.l Nevertheless, the need for compounds soluble in organic solvents and insoluble in water. (1) A. Gilman and F. S. Philipr, Science, 108,408 (1046). (2) L. S. Goodman, M. M. Wintrobe, W. Domeahek, M. J. GoodIn ethanol-water solutions i t reacts slowly t o form the bis-cyclopentadienylcobalt (111) cation in man, A. Gilman and M. J. McLennon. J . Am. Mird. AJSOC..lSS, 126 (1940). greater than 70% yield.
tyrl.lglul.lhiso.Bphel.oargo.oglyl.oe-tosy1sl.o. Met, val and pro present but not determined. The final product and a number of intermediates were assayed for melanocyte expanding ability, l S . l 4 with the following results which are expressed in MSH units per gram : his.phe.arg.try.gly 1.5 X 1O4; his.phe. arg.try .gly.- e- tos1ys.pro.va1. amide 0.5 x lo6; cbzoser.tyr.ser.met.gluta .his.phe .arg.try. gly .-E- tosly s.pro .Val. amide 0.8 x 108. From these results i t is apparent that our blocked tridecapeptideamide possesses essentially the same MSH activity as the corticotropins, and that it is one per cent. as active as a-MSH.
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(1) G. Wilkinson, F. A. Cotton and J. M. Birmingham, J . Iaorp. and Nuclear Chrm., II, 95 (1955).
(3) S. Farber, R. Toch, E. M. Sears and D. Pinkel. in “Advsncu In Cancer Research.” J. P. Greenstein and A. Haddoa, editorr, Academie Press, Inc.. New York, N. Y., Vol. IV,1956, pp. 20-33.
