Aug. 5, 1960
COMMUNICATIONS TO THE EDITOR
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dipole moment measurements ( ~ I I = 6.4 0.5D andp, = 4.6 f.0.50).6 The compositions and structures of the products of the systems based upon M e A l and isoBu&J apparently are not known, but the formulations Cp2TiC12AlR2, where R = alkyl, may well apply. For R = Me, the e.s.r. spectrum is consistent with this assumption, whereas the large width of the spectrum observed in the case R = iso-Bu cannot be explained in this way, if the treatment used to explain the widths of the other spectra is correct. The hyperfine pattern given by the iso-BuAl product is consistent with the interaction of the electron spin with the A12' nuclear moment and with two equivalent protons which have equal coupling constants.' The e.s.r. results suggest that the final paramagnetic product of this reaction is not of the same structural type as given by the other aluminum alkyls which we have studied. We gratefully acknowledge the support of this work by the Office of Naval Research and the National Science Foundation.
Its ultraviolet spectrum is very similar to that of 1,1'-dimethylferrocene,2 containing a weak maximum a t 320 mp (Emax 492), a shoulder a t 250 mp ( E 4,920), and high end absorption ( E Z ~13,600). Although the ultraviolet and infrared spectra of I are characteristic of alkyl ferrocenes, the n.m.r. spectrum is The n.m.r. spectrum of the close analog, 1,l'-diisopropylferrocene contains a single peak due to the ferrocene ring protons ( T = 5.97),5 together with the expected doublet (7 = 8.86) and multiplet4 (T = 7.36) due to methyl and methine protons, respectively. Similarly the spectrum of 2,3-diferrocenyl-2,3-dimethylb~tane~ contains three singlet peaks a t 7 = 8.69 (methyl), 5-94 (unsubstituted ring) and 5.86 (substituted ring). The spectrum of I contains the expected methyl proton singlet ( T = 8.74)) but the ring protons are found in two widely separated triplets ( T = 6.11 and 5.37; J = 1.6 c.s.). The considerable chemical shift is best explained as arising from the ring protons' unequal distance from the iron nucleus in a molecule where the rings are DEPARTMENT OF CHEMISTRY AUGUSTH . MAKI tilted; this interpretation is thus in accord with HARVARD UNIVERSITY EDWARD UT.RANDALL the mono-iron molecular weight above. CAMBRIDGE 38, MASSACHUSETTS Since protons close to a transition metal nucleus RECEIVED JUNE2, 1960 have been shown to give n.m.r. peaks a t relatively higher field in similar compounds (cf. cyclopenta1,I '-(TETRAMETHYLETHYLENE)-FERROCENE. dienylcyclopentadienecobalt),7 the ring 2-protons OBLIQUITY AND N.M.R. IN BRIDGED FERROCENES are assigned to the higher field peak ( r = 6.11) Sir: and the ring 3-protons to the lower ( r = 5.37). Similar two-carbon bridged ferrocenes are formed We wish to report the preparation and properties of 1,l'-(tetramethylethy1ene)-ferrocene (I), con- from other fulvenes*; however, an alternative reactaining an unusual two-carbon bridge linking the tion path can predominate. Thus, the major product from treatment of cyclopentylidenecyclotwo cyclopentadienyl rings.
i
2.00
3.00
4.00
5.00
7.00
6.00
8.00
9.00
10.00
7
Fig. 1.
Treatment of 6,6-dimethylfulvene' with sodium pentadiene (6,6-tetramethylenef~lvene)~ with sometal dispersed in tetrahydrofuran, and then dium, then ferrous chloride, is 1,l'-di-(1-cycloferrous chloride, gave a mixture in which the major pentenyl) -ferrocene (11), m.p. 108-109 O [Anal. product (albeit in low yield) was the bridged comJ. Bellamy, "The Infra-red Spectra of Complex Molecules," pound (I); red crystals, sublimes 130' (8 mm.), 2nd(3)e dL.. , John Wiley and Sons, New York, N.Y.,1958, p. 13. m.p. 168-169' (crystal modification 129-130') (4) Additional differences between bridged and non-bridged alkyl [Anal. Found: C, 71.83; H, 7.62; Fe, 20.68; ferrocenes, to be discussed in the complete paper, are lower stability (standing, as crystals or in solution) and decreased reactivity (toward mol. wt. (cryoscopic), 2851. acylation) of the bridged compounds. Detailed disThe infrared spectrum of I is generally similar Friedel-Crafts cussion of n.m.r. spectra, in particular of splitting, is also deferred to to t h a t of 1,1'-diisopropylferrocene, with bands the full report. a t 3100, 917 and 850 cm.-I (alkylferrocene),2 (5) G.V. D.Tiers, J . Phys Chem., 69, 1151 (1958). 1451, 1377 and 1367 crn.-l (gem-dimeth~l).~ (6) K . L. Rinehart, Jr., P. A. Kittle and A. F . Ellis, THISJOURNAL, sa,
(1)
G.Crane, C. E. Boord and A . L. Henne, THISJOURNAL, 61, 1237
(1945). (2) K . L. Rinehart, Jr., K . L. Motz and S. Moon, i b i d . , 1 9 , 2749 (1957).
2082 (1960). (7) Cf., c.g., G.Wilkinson and F. A. Cotton, Progr. in Inorg. Chem., 1, 1 (1959), and Ref. 1.3 therein. ( 8 ) R . L. Pruett and J. E. McMahon, unpublished results. (9) E.P. Kohler and J. Kable, THISJOURNAL, I T , 917 (1935).
COMMUNICATIONS TO THE EDITOR
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Vol. 82
partial support of this research. Financial assistance also was provided in part by the hiaterials Laboratory, Wright Air Development Division, Wright-Patterson Air Force Base, Ohio. (14) Undergraduate Research Participant, supported by a grant N S F G-8521) f r o m t h e National Science Foundation.
DEPARTMENT O F CHEMISTRY KENNETH L. RINEHART, JR. CHEMICAL ENGINEERING ALMUTK. FRERICHS UNIVERSITY OF ILLINOIS PAULA. K1TTLEl4 URBANA, ILLINOIS LARSF. VESTM MAN DAVIDH. GUSTAFSON UNIONCARBIDECHEMICALS COMPANY ROYL. PRUETT SOUTH CHARLESTON, WESTVIRGINIA THELINDECOMPANY JOHN E. MCMAHON NEWYORE TOXAWANDA, RECEIVED JUNE 13, 1960 AND
L-.--.,. -~ L ~ -.~ L .~ .~~ ,
L
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8.00
~
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6.00
7.00
-
_,--..A2
9.00
10.00
7
Fig. 2.
Found: C , 75.50; H, 7.16; Fe, 17.541. In this reaction sodium presumably functions as a base to give the alkenyl cyclopentadienyl anion from the fulvene much as does sodium amide in an alternative preparation of alkenyl ferrocenes.lolll The structure I1 may be assigned on the basis of its infrared spectrum (conjugated C==C stretching band at 1630 cm.-l) and ultraviolet absorption (Amax 273 mp, Emax 13,700).' Conclusive evidence is derived from the n.m.r. spectrum, which contains an olefinic proton (triplet) a t ( T = 4.33) , 4 While the rings are sufficiently canted when spanned by a two-carbon bridge to cause chemical shift of the ring protons, this is apparently not the case with simple saturated three-atom bridges. Thus, the ring protons appear as a singlet in both 1,l'-(trimethylene)-ferrocene (111)12 (T = 6.05) and 1,l'-(dimethy1eneoxy)-ferrocene (IV) l 3 (T = 5.88), m.p. 148" (sinters 100') [Anal. Found: C, 63.34; H, 5.44; mol. wt. (isothermal distillation j , 233 1.
Acknowledgment.-Acknowledgment is made to the donors of The Petroleum Research Fund, administered by the American Chemical Society, for (10) P. L. Pauson. G. R . Knox, J. D. Munro and J. M. Osgerby. X V I I t h International Congress of Pure and Applied Chemistry, Munich, August-September, 1959, cf. Angezo. Chem., 72, 37 (19GO). (11) A cyclopentenylferrocene has been prepared previously hy reaction of ferrocene with hot hydrogen fluoride under pressure [V. Weinmayr, THISJOURNAL, 77, 3009 (1955)l. While this reference does not assign t h e position of t h e double bond, its ultraviolet spectrum, (A,,, 275 m r , emaa 10,400) allows the double bond t o be located in conjugation with t h e ferrocene ring, as in the di-substituted 11. (12) A . Liittringhaus and W. Kullick, Angew. Chem., 7 0 , 438 (1958). (13) Compound IV was prepared by treatment of 1,l-di-(hydroxymethyl)-ferrocene (V) with p-toluenesulfonyl chloride in refluxing benzene. Compound V, m.p. 107-108° [Anal. Found: C, 58.85; H,5.771, in t u r n , was prepared by lithium aluminum hydride reduction of dimethyl 1.1-ferrocenedicarboxylate, a method employed previously [ A . N . Xesmeyanov, E . G . Perevalova and Z. A . Beinoravichute, D o k i a d y A k n d 2 V n ~ i kS . S . .S. R.,112, 430 (1957)] the earlier authors reported m p S i - 8 0 ° .
ACYL- FROM ALKYL-FERROCENES BY MANGANESE DIOXIDE OXIDATION. FERROCOBENZOQUINONE
Sir: -4lkyl ferrocenes frequently may be prcparcd directly from alkyl cyclopentadienesl and could provide useful starting materials for the preparation of functionally substituted ferrocenes if the alkyl groups could be oxidized selectively without concomitant or preferential oxidation oi the icrrc,cerir nucleus to ierricinium ion. In the prcsent, initial studies toward this end innngancse dioxide (which usually selectively oxidizes dlylic or benzylic alcohols to the corresponding conjugated carbonyls,? and which has been used for conversion o i hydroxyrrictliylferrocene to icrrocenecarboxaldehyde/j" \vas selected LIS a mild, heterogeneous oxidant and shou-n to oxidize readily alkyl ierrocencs to the corresponding acyl conipollllds. 31ethylferrocene3 was heated fur two days with :I large excess of activated manganese dioxide jcmnmcrcial, Beacon Labs.; in refluxing methylcyclohexane.: Chromstography oi the p r d u c t gave 53C; of recovered methylierroceiic and :I 5 2 7 yield (based on unrecovered methylfrrroccnr, i . ~ .:I , 237, conversion) of ierrocenecarboxaltl~liy(l~, ( 1 ' ( a ) 1'. I . Pauson T H I S J o I . R v . % I . , 76, 21s; :l95-1)' !I)' K . I.. Ilinehait, J r . . K. 1.. I I o t z and S !.Ihon, ibii , 79, ? 3 9 'lit,;':;; ' c ! K E. Benson and R . l' T.indsey, i h i d . , 79, 5471 (1957;; ~ d K ' I.. I i i d . L o n l m ) . !I.X (!!I-R i n e h a r t , Jr.. and I;. 1.. I l o t z . CI!eni c ) R . C. Koestler and 1". F. Little, i b i f . , 1389 '1938); (i: G R . Kncjx mid P. L. Pa:ison, P r o r . Chenz S x , 289 (1938), ( g ) 1, 1'. K e y n d d s a n d G. \\'ilkinson J. I n o g an! .Y:,(/. C'l:p?n, 9, 80 ( l % i < , \ : .hJ P. 1.. Pauson, G. R . Knox, J. D. l l u n r o and J. 11, Osyerby, .4i:&'rv. C / I P I I,I 73, 3': '1900). ( 2 ) For recent reviews ~f manganese diuxide oxidations, cf. R I f . lirans, U u a f R P : ~(IA9?zdcn), . 13. G 1 (l559), and C 1) Kobswn, or.: Chem. Ball., 32, S o 2 ' 1 9 6 0 ) . Other oxidations I J mrnqnncse ~ rlit>.;ide, though less cnmfuun have becn reported. l o r crampls, tfiJl!une and o-nitrotolucne gave the ccrrespondinq venzaldehyks an1l:i~r bPnzGiC acids with manganese dioxide in sxlfuric acld [ F Kaschig, ('heniikcr Ztg., 24, 41G (1500):. while the allylic ring methylene g r m p of vitamin A! and of reinene was oxidized t o the corresponding nlly!ic alcohol or t o t h e o,B unsaturated ketone. or unsrtarked. depwding o n the manganese dioxide employed [H. D. IIenhest. E . R. I i . J a e s and I' C O w n , J Chem. S . c -1900 10.57, I. '8) A . S . Sesmeyanov, E G. Perevaluva. L. S Shilootceva and Z . A . Heinoravichute. D . i k / o j y : l k i ? \ i i d ' S 3 S R , 121, I I: \I i.78). ! I \ T h e conditions descrihed are not CI niidered optimum. experiincnt:iI re>iLlts in this directisjn w i l l bc trcttcd in the f u l l paper.
