5771 Scheme I. Formation of Radical Cations in the Oxidative Solvolysis of Ni(SG(CH3)2)2and Related Reactions
not observable
\
known;'I2 our picture of this reaction is thus limited by the lack of information regarding the existence and nature of dihydro intermediates. An attempt to obtain such information was made by Lemal and Shim;3 having observed no intermediate in the reaction 1 + 2, they proceeded to demonstrate the stability of the (independently prepared) dihydro derivatives 3 and 4 to the conditions of the reaction and could therefore exclude them as intermediates. The formation of 2 was then tentatively interpreted as involving simultaneous hydrogenolysis of two bonds.
g = 2.014
= 2.06
G
Here we wish to report that from the hydrogenolysis of our steroidal bicyclobutane derivative 5-itself of considerable interest4-a unique dihydro product, 6, can be obtained in high (>80 %) ~ i e l d . ~ ? ~
n
tronic structure of the anion Ni(S2C2H2)2-,as well as the 33S and 'Ni esr hyperfine interaction measurements for Ni(MNT)2- of Schmitt and Maki.g The groundstate electronic configuration of these anions is 2B2g; for R = H the calculated C, S , and Ni(3d,,) spin densities are 0.0256, 0.0969, and 0.5 10, respectively. The low spin density on carbon is responsible for the absence of resolved hf splitting in the esr spectra of Ni(S2C2H2),- and the CH3-substituted derivative. The esr signals of the radical cations 2 exhibit pronounced threefold anisotropy if examined in H,S04-CH,N02 glass at 100"K, which thus is partly responsible for the threefold anisotropy of the signals of the ions M(S2CzR&-. The oxidative solvolysis of various metal trisdithienes produces esr signals of type I1 in 40-80 wt% HzSO4 in CH3N02. The decomposition of W(S2C2(CH3)2)3and of (CH&C&Ni.Lig (Lig = (C~HS)~P-(CH,),-P(C,H~)~ in 5 1 0 % H2S04-CH3N02 yields a new symmetrical seven-line esr signal at ( g ) = 2.009 with ( a H )= 6.1 G, which we consider to be due to the dimethylthiirene radical cation. Work to characterize this species is in progress. Acknowledgment. This work was supported by Grant No. 3486/A 3 of the Petroleum Research Fund, administered by the American Chemical Society, and from Institutional Grant No. G P 5208 of the National Science Foundation. (9) R. Schmitt and A . H. Maki, J . Amer. Chem. Soc., 90,2288 (1968). * Address correspondence to this author,
G . N. Schrauzer,* H. N. Rabinowitz Department of Chemistry, Reuelle College University of California, Sun Diego, La Jolla, California 92037 Received M a y 8, 1970
A Steroidal Bicyclobutane and Its Hydrogenolysis
Sir : From previous studies of the hydrogenolysis of bicyclobutane systems, only tetrahydro products are
5, mp 161-162'
[alD
+ 51.8'
n
6, mp 101.5-103° , b l D
- 31.6'
On stirring the solution of 5 in acid-free ethyl acetate under Hz(760 mm) with a prehydrogenated Pd-C 10 catalyst, the initially rapid gas uptake slows abruptly after 1 equiv has been absorbed (3-4 min). Work-up at this point allows 6 to be obtained. With deuterium gas, the reaction proceeds analogously and both D atoms appear in the 8a-methyl group of 6 (nmr).? This, we think, is the first recognized case of what may be called geminal hydrogenolysis with the concomitant formation of a C=C double bond and we propose the following rationalization. The catalyst, approaching 5 from the a side, would first add one H to the most protruding (and, incidentally, most acidic-see below) site C7 under the cleavage of bond C&7 and the development of a delocalized C6 radical, 8. A second H would then be delivered to the same site, accompanied by the fission of C7-C7aand the formation of the C&7 (1) For a review, see I
