COMMUNICATIONS TO THE EDITOR
Sept. 5 , 1961
3727
tion of I occurs by disproportionation, half being time of standing, but in a typical run (96% H?SO( dehydrohalogenated to butadiene irontricarbonyl for 2 min.) the products are pentaphenylcycloby the other half, which in turn decomposes to pentadiene (111), 23%, 1,2,3-triphenyl-lH-cycloferrous chloride, carbon monoxide, and but-2-enes. penta [ 1]phenanthrene (IV), 48%, 2,2,3,4,5-pentaSuch a mechanism is in accord with the stability of phenyl-3-cyclopentene-1-one (V), 5%, and an amorphous oxygen-containing material which has I in the melt or in solution. It is interesting to note that the spectral data not yet been identified, 21y0. This latter does not indicate that I is not a mixture of isomers, as was form pentaphenylcyclopentadienyl chloride with chloride in acetic acid under conditions found to be the case with the cobalt c o m p l e ~ . ~hydrogen ,~ IVhile such evidence is not definitely conclusive, it in which I is quantitatively converted to the seems reasonable, from the mode of formation of I, chlorideI2and it gives a brown solution in sulfuric that the geometry of the C4 moiety in butadiene acid. Compound IV, m.p. 220-22lo, has mass 444,5 irontricarbonyl might be maintained on conversion to the a-allyl complex. On this basis, it is sug- C35H?4(C, 94.26; H, 5.52). In the n.m.r. it has a gested that I isolated as described above is the anti one-proton singlet a t 4.73 T , a two-proton multiplet a t 1.48 r which is characteristic of the 4,s hydroisomer (Iva). An X-ray study of the structure of I is currently gens of a phenanthrene,6 and a twenty-proton under way.6 Alternate synthetic routes for the multiplet a t 2.85 r . ,411 together these data established the structure IV (or, less likely, IV’); preparation of I also are being investigated. We are indebted to Dr. T. H. Coffield for sugges- the structure was confirmed by synthesis. Phentions leading to the carrying out of the initial reac- cyclone with phenyllithium yielded VI, m.p. 222223O,’ (C, 90.28; H, 3.31), which with thionyl tion. chloride and pyridine yielded VII, m.p. 253-254’, (6) X - R d y studies are being carried o u t b y Professor L. L. Dah1 of (C, 87.47; H , 5.01). Treatment of VI1 with zinc the University of Wisconsin. in acetic acid afforded IV, identical with the preETHYLCORPORATIOS F. J . IYPSSTATO DETROIT,MICHIGAX K. G. IHRMANviously obtained material. Structure IV’. and an analogous one for the chloride VII, are ruled out RECEIVED JULY 17, 1961 by the ultraviolet spectra; AXma, ( E ) : VI, 251 (34,000), 281 (30,000), 415 (3,600); VI1 230 THE REARRANGEMENT OF THE (37,000), 352 (4,000); IV, 233 (40,000), 315 PENTAPHENYLCYCLOPENTADIENYL CATION’ (12,000) mp.s The structure of the ketone (V), Sir: m.p. 194-195’, (C, 90.67; H, 5,69), is indicated by Some time ago Ziegler2reported that the solution the fact that its formation is reversible, since on of pentaphenylcyclopentadienol (I) in concentrated standing in sulfuric acid it affords TI1 and IV, and sulfuric acid contains a purple species which he by spectroscopic data indicating an unconjugated considered to be the pentaphenylcyclopentadienyl cycl~pentenone~ : infrared, 5.76 p , ultraviolet, 261 cation (11). He reported that this solution, mp (13,000); in the n.m.r. it has one proton a t 5.25 poured into water, afforded a material which was ‘T and twenty-five protons in a multiplet a t 2.83 r . “evidently the dimeric ether” of I. On the basis Compound I11 was identified by comparison with of spectroscopic studies Bloom and Krapcho3 con- an authentic sample.? cluded that the colored species was indeed 11, but The spectrum previously assigned to I1 is simply they did not further investigate the supposed the composite spectrum of I11 and I V in sulfuric dimeric ether. Because I1 is a derivative of the acid. Thus I11 in sulfuric acid forms a bright cyclopentadienyl cation in which the five-fold orange solution, AXmax 302 (32,400) and 443 mp symmetry ( D b h ) is retained it is of particular in- (18,700) from which I11 is recovered quantitatively terest, since it is also predicted to have a (possible) on dilution. The solution of IV in sulfuric acid triplet ground state. The stability and nature of has AX,, 520 (26,500) and 376 mp (13,000). The such species is still an open q ~ e s t i o n . ~ Accord- spectrum of I in sulfuric acid,, , ,A 516 mp (20,500), ingly we have examined the sulfuric acid solution can be reproduced quantitatively by an approof I in some detail, and find that after a few seconds priate mixture of 111 and IV. The spectra are none of the cation I1 is present. ascribable to one or the other of two possible processes:1° (a) protonation of 111 and IV to carC&L
c6H5qc6H5 ( 5 ) T h e mass spectrum was obtained through t h e courtesy of D r .
c6H535$c6H5
CsHj Cs& C6H5 x I,X=OH 111, X = H
csH5 C6Hj 3 I1
When the solution is poured into water a mixture of products is obtained whose exact composition varies with the strength of the acid and the (1) This work was supported by a grant from t h e National Science Foundation, which is gratefully acknowledged. (2) K. Ziegler a n d B. Schnell, A n n . , 441, 266 (1925). (3) S.M.Bloom a n d A. P. Krapcho, Chem. and Ind.,882 (1959). (4) For evidence on t h e possibility t h a t tetraphenylcyclobutadiene has a triplet ground state, cf. H.H. Freedman, J. A m . Chem. SOL, 83,2196 (1961).
B. Dudenbostel of Esso Research Laboratories. (6) J. A. Pople, W. G. Schneider, and H. J. Bernstein, “Highresolution Nuclear Magnetic Resonance,” hIcCraw-Hill Book Company, Inc., S e w York, N. Y., 1959. p . 248 ff. (7) T h e compound of m.p. 255-257O. prepared by \‘. Abramov and P. Malskii, J . G r n . Chem. U . S . S . R . , 9, 1533 (19:iO) by the reaction of phencyclone with phenylmagneiium bromide, is a ketone resulting from conjugate addition, and dues not have the structure ( V I ) which they assigned. (8) This slight change when the chloride is converted t o a hydrocarbon is mirrored in the pentaphenylcyclopentadiene series; t h r ultraviolet spectrum of pentaphenylcyclopentadienol resembles t h a t of the corresponding chloride and hydrocarbon. (9) C j . C.F. Allen, J. A. VanAllen and J. F.Tinker, J . Org. C h e w . , ao, 1387 (1955). (10) S. I. Weissman, E. deBoer and J. Conradi, J . Chem. P h y s . , 26, 963 (1957); W. Aalbersberg, G. Hoijtink, E. Mackor and W .
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T.’ol. s3
COMh1UNIC“iTIONS TO TIIE EDITOR
bonium ions, or (b) reversible electron abstraction from I11 and IV to form cation radicals. These radicals have been detected by strong e.s.r. signals11 froin the sulfuric acid solutions of I, 111, and IV 20 gauss, g -2.00) and considerable line (width I m d e n i n g in the n.m.r. ; the paramagnetic species, as expected, are not oxidized by bromine.
reported the preparation of niobium dihydride. We wish to report the synthesis of the corresponding but non-stoichiometric dihydride of vanadiuin. For our study of metal-hydrogen systems in tlic. high pressure regions we employed a modified 300ml., stainless steel, commercial hydrogenation apparatusa In place of the solenoid-actuated dasher, a 1.25-cm. diameter ball of tungsten carbide brazed to the actuating-rod was used. A stainless steel, mortar-shaped insert reduced the volume to 100 ml. Hydrogen was purified by passing it over a hot uranium bed and the pressure was measured with a 0-5000 p.s.i. Heise gauge. The bomb was charged with 6 g. of VH0.40,evacuated and filled IV’, X = H IV, X = H with hydrogen to a pressure of 70 atm. The VI, x = O H VII, x = c1 sample was crushed in two &hour periods with the greatest hydrogen uptake during the first period (AP = 12.5 atm.) and a smaller amount during the second (AP = 2.0 atm.). The calculated composition from the drop in pressure was VHIR. 0 uri Analysis by thermal decomposition and rneasurement of the hydrogen evolved gave VH1.45 + o 05. v VI11 After hydriding, the sample was removed from It seems likely that I11 and I V are formed via the bomb in a protective argon atmosphere and 11, and indeed a transitory color is seen when I dis- packed into 0.5 mm. thin-walled glass capillaries. solves in sulfuric acid, but I1 apparently is quite Examination by powder X-ray diffraction tech~ n s t a b l e . ’ ~By contrast, we find that both tri- niques, using a G.E. XRD-4 unit and copper radiaphenylindenol (VIII) and 9-phenylfluorenol give tion, showed the presence of a f.c.c. phase along unrearranged carbonium ions in sulfuric acid (df with the b.c. tetragonal monohydride. diter cor~ K R- 12.6 and - 10.8, respectively) ; these recting for film shrinkage, the lattice parameter derivatives of the cyclopentadienyl cation, unlike of the f.c.c. phase was determined from a plot of 11, are not calculated to have degenerate ground a versus the h’elson-Riley f ~ n c t i o nand , ~ was found states. Although it is particularly easy t o for- to be 4.270 f 0.002 if. We believe the hydrogen mulate the rearrangement of I1 to IV in terms of a atoms occupy tetrahedral sites in the f .c.c. vanadiradical, it cannot necessarily be concluded that a dium lattice giving the new compound a fluorite, triplet is involved. Accordingly, the nature of C1 type structure a t VH2. A calculation of the exthe ground state in such species remains an open pected internuclear distance ( d m 3 ) for this strucquestion. ture using Q.59 A. for the radius of the vanadium Vfeijland, J Chem. Soc., 3049 (1959); J. Rooney and R. Pink, Proc. ion,10 1.40 A. for the radius of the hydride ion,” Cizem. Soc., 142 (1961). and applying the proper coordination number cor(11) The e.s.r. spectra were obtained by XIr. Philip Rieger of these rectionsI1 gave d b r H = 1.89 k . The observed dislaboratories. tance is 1.85 A. (12) Studies of t h e rate of color development from I and from VI11 in solutions of varying FIR show t h a t t h e ~ K Kof I1 is - 10 or less. Several attempts were made to increase the hydrogen content. These included increasing the DEPARTMENT OF CHEMISTRY COLUMBIA u N I V E R S I T 1 ’ RONALD BRESLOW pressure in the bomb, lowering the temperature of S l S W YORK, x E \ V I‘ORK HAI Wox CHANG the bomb by immersion in a thermostatic bath and RECEIVEDMAY19, 1901 using up t o eleven hours of crushing time. I n one of these runs, we succeeded in preparing a material which analyzed as VH1.83,but the analysis may not A NOVEL HYDRIDE OF VANADIUM’ have been carried out on a representative sample. Siv: 006 (bomb In another run, we obtained VH164 The group VB metals (V, Nb, Ta) react with pressure 136 atm., temperature -2’, crushing time hydrogen a t moderate temperatures and atmos- eleven hours). A n X-ray diffraction powder pheric pressure to form hydrides approaching photograph of this hydride showed a large propL)rMH.2-5 The non-stoichiometric monohydrides of tion of the f.c.c. phase (ao = 4.271 0.002A.) tantalum and niobium have a face-centered ortho- along with the b.c. tetragonal phase. rhombic structure,6 while VH0.47-0.81 is bodyAccording to Brauer and niobium dicentered tetragonal. Brauer and Muller’ recently hydride can be prepared by electrolysis and also (1) T h i s research was supported by t h e U. S. Atomic Energy by treating finely divided niobium monohydride Comrnissiot~. (or Nb powder) with 10% HF. We have adopted (2) L. Kirschfeld and A . Sieverts, 2.Elektuochetn., 86, 123 (1930). this latter procedure to prepare vanadium dihy(8) P . Kofstad and TIV. E. Wallace, J . A m . Chem. Soc., 81, 5019
-
+
+
*
(1959). (4) W . h l . Albrecht, 11. 1%‘. Mallett and UT. D. Goode, J . Eleclrochem. Soc., 106, 219 (1958). ( 5 ) A. Sievertsand H. Moritz, J . nnorg. allgem. Chem..247,124 (1941). (6) G. Brauer and R. Hermann, 2.a t i o y g . Chem., 274, 11 (1953). (7) G. Brauer and H. Mflller, Aizgew. C h e m . , 70, 53 (1958); J . I n o r g . Nucl. Chem., 17, 102 (1961).
( 8 ) Made by .4utoclave Engineers, Erie, Pa. (9) J. B. Kelsou and D. P. Riley, Pvoc. P h y s . S o c . , ( L o i z d u t r ) , 67, 160 (1945). (10) Landolt-Bbrnstein “Tabellen,” Vol. I. “Kristalle,” Pt. 4 , A. Eucken, Ed., Springer-Verlag, Berlin, 6th Ed., 19.50, p. 523. (11) T. R. P. c i b h , Jr.: a n d D. P. Schomacher, J . P h y s . C h x . , 64, 1407 ( 1 D G O j .
