2394
~ O M M U N f C X T I O S STO T H E
EDITOR
Val. bY
titanium dichloride (I) or its zirconium analog TABLE I (11) has been found. LVilkinson and Birmingham2 BIS-CYCLOPESIADIEX~YL TITANIUM DICHLORIDE demonstrated from infrared data that a monomeric Concn Dielectric Dmsity (wt. fract.) constant e (g./cc.) 7% (qo)? s-bonded “sandwich” structure exists for I and 11. 0.000869 2.281 ... Sloan and Barber3 reinforced these observations ,001‘329 2.300 ... by- proton magnetic resonance data on I and 11, ,002870 2 ,313 ... but no mention has been made o€ the spatial con,00169 2.290 0.8695 .. ... figuration of the rings. 000615 2 279 ,8690 ... ... “Xngular” sandwich structures have been postu.000327 2.269 ,8689 ... ... lated for bis-cyclopentadienyl tin and lead on the Solvent 2.265 ,8684 ... ... basis of dipole moments and other measurements,4 and X-ray measurements on (C5H&TiC12.illL ZIRC0.YIC.M L)ICHLOKIDE Concn. (C2H5)2 JIII).’ (wt. fract.) 730D (1ID)S 11-e wish to report that the hzgh values of the 0,002978 2.303 1 ,49439 ‘1 23337‘3 dipole moments obtained, 6.3 and 5.9 D for I and 1 .49454 2.23363 ,001951 2.291 11, respectively, indicate that there are four es.001052 2 276 1.19448 2,23347 sentially equivalent bond angles and that the 1 ,49440 2 23323 ,000472 2.273 structure is similar to the [ (CjH&TiCls ] grouping Solvent 2 . 2 6 5 1 49139 in 111, i.e., approaching the tetrahedral configuration as depicted in Fig. A . I t is of interest that temperature controlled to O.O.Jo. Densities were the structure appears to be independent of the measured in a 23 ml. pycnometer.fi oxidation state. The data were interpreted by the method of Guggenheim and Prue’ and of Halverstadt and Kumler.8 least squares analysis was applied with these results. Ti CoIrlpound I Zr Compound I1
+(Debyes)
liethod
6.26 i0,39 6 . 2 % zk 0.39 3.90 z!= 0.38
Refractive iiidcs Density
Refractive index
The uncertainty given represents the 937; confidence interval of the data. ( 0 ) Tlre dielectric constant, refractive index a n d density measurements were performed by J. R. Murray of these Laboratories. (7) E. -4.Gupgenheim and J. E . Prue, “Physicochemical Calculations,” Interscience Publishers, Inc., New York, N . Y , 1935, VI). IOfi, el seq.
(8) I . F. Halverstadt and U‘. D. Kumler, J . A r i ? . Chcii?. S O L , 64. 2Y88 (1942).
Fig. 1.
The measurements were conducted in benzene using the “dielectric constant-refractive index” method for I and 11, and the “dielectric constantdensity” method for I. Measurements made both on freshly prepared solutions and on solutions one day old were identical, suggesting that changes in solution, if any, had no effect on the dielectric constant. The results are shown in Table I. Dielectric constant measurements were made a t 30.0° using a heterodyne-beat circuit consisting of two electron coupled oscillators, one controlled with a quartz cryshl a t 5 i 6 . 3 kc. and the frequency of the other one controlled by the variable capacitance. X Balsbaugh model cell made of Pyrex and monel metal was used. The volume was 50 nil., and the interplate air capacitance was 39.4 p p f . Refractive index was measured with a Bausch and Lomb Precision ,ibbe refractometer, ( 2 ) G . Wilkinson arid J . .\I. Hirmingh;irn, J . .Ain. Chciii. S a . , 76, 4281 (195li 13) C I.. SIoan and LV.A Rarher. 9 fl) 1. D. l3.rx.e. I> I‘ I~:vansancl C ( 19 .XI). (S) G. Nxtta, F. Curradini arid I . \V, Bassi, J . 21;i~.Chciii. Sac., 8 0 ,
-i -~- . (1958). )
CHEMICAL RESEARCH A N D RESEARCH SERVICE DEPARTMENTS CENTRAL RESEARCH DIVISION S. .I.GIDDISGS R. J. BEST -&ERICAN CYANAMID COMPAXY STAMFORD, CONSECTICUT RECEIVEDMARCH 25, 1961 THE CONFORMATION OF METALADENOSINE TRIPHOSPHATE COMPLEXES IN SOLUTION
Sir: The fact that adenosine triphosphate (4TP) forms strong complexes with divalent metal ions is well known and quantitative and kinetic studies3have been caried out by several workers. The most important metal binding sites are undoubtedly the phosphate groups, but the role of the rest of the molecule in forming the metal complex has given rise to much speculation ( c f . reference 4 for a review of this subject and pertinent literature citations). Solid state infrared studies, (1) A. II LZartell and G . Schu-arzenbach, H e l w . Ch$iii A l c l a , 39, 033 (183fi).
( 2 ) R. A . Albertp a n d 11. M . Smith, J . . l i n Chc~li..S’oc., 78, 237H ( I 0 SFi). I,’() H.
Uiehler, A I I-igen and C;. C;. Iinmrnes. i!
1SB. . i R 1 (1960). (i)Yi K. Atkinson and I 6 ) the n.m r. (and apparently ultraviolet) spectra are unchanged by the presence of Mg++, the assumption of a folded conformation on the basis of the above mentioned data is not warranted.
GORDON G. HAMMES DEPARTMENT OF CHEMISTRY INSTITUTE OF TECHNOLOGY MASSACHUSETTS GARYE. MACIEL CAMBRIDGE 39, MASSACHUSETTS J. S. WAUGH RECEIVED MARCH15, 1961 DIRECT AND SENSITIZED PHOTOLYSIS OF ETHYL PYRUVATE
Sir : We have observed that irradiation of benzene solutions of ethyl pyruvate leads to photolysis or' the a-ketoester. The principal products are carbon monoxide and acetaldehyde, indicating the path C H ~ C O C O ~ C ~+ H2CH3CHO E
+ CO
associated with the adenine portion of the A T P molecule. A word of caution should be inserted here : this interpretation assumes implicitly that adding positive charge with Mg++ would produce the same general effect as adding a proton to one of the rings. Since the protonic charge is thought to distribute itself throughout the pyrimidine ring in ATP,6 Mg++ might conceivably form a loose type of complex with the amino group where no charge transfer to the pyrimidine ring occurs ;
A small amount of carbon dioxide also is produced. It was of interest to learn whether or not the fragmentation reaction involved a singlet excited state or a long-lived triplet. The latter possibility is suggested by the fact that irradiation of ethyl pyruvate in ether-pentane-alcohol glass a t 77' K. gives rise to a weak, blue phosphorescence. In order to establish the decomposition mechanism we used benzophenone as a photosensitizer for the decomposition of the ester. Hammond, et ul.,I and Backstrom and Sandros2have shown independently that excitation of benzophenone in solution is followed by quantitative intersystem crossing ; therefore, the chemically significant excited stat e
( 5 ) C D Jardetzky and 0 Jardetzky, J . A m . Chem. Soc , 82, 222 (1960). (6) R. M. Bock in "The Enzymes," (P. D. Boyer, H Lardy, K. Myrback, e d ) , 2, Academic Press, Inc., New York, N . Y., 1960, p p 3-38.
(1) G. S. Hammond and W, hl. Moore, J . A m . Chem. Soc., 81, 6334 (19.59); G.S. Hammond, W. M. Moore and R . P. Foss. i h i d . , in press. (2) H. L. J. Backstrom and K. Sandros, J . Chem. Plays., 23, 2197 (1955).
