CYCLOPENT.~DII:NYL~I.~NG,~~ESE TRIC.~RUOKYL COMPOUNDS
June 20, 1'339
2996
ORGANIC AND BIOLOGICAL CHEMISTRY [COs~TRIBUTIONF R O M THE
DETROITRESEARCH L A B O R A T ~ ROIFEETHYL S CORPORATION]
The Chemistry of Cyclopentadienylmanganese Tricarbonyl Compounds. I. Acylation and Alkylation1 BY JOIIN KOZIKOWSKI, RAYMOND E. ~ L I G I NAND N MARCELLA SIZENKLOVE RECEIVED SEPTEMBER 8, 1958 Cyclopetitadieiiyltii3~ig~~iese tricarbonyl 113s becn acetylated and benzoylatcd and the cyclohcsyl and t-butyl derivatives prepared. By a series o f competitive reactions it has been shown that a s regards reactivity toward acylation, a series can be established in order of decreasing activity-anisole > rrlethylcyclopentadienylmanganese tricarbonyl > cyclopentadicnylmanganese tricarboriyl > benzene. Benzoylation of methylcyclopentadienylmanganese tricarbonyl gives rise t o two isomeric compounds in the ratio 3 to 2.
Ferrocene, which has a type of penetrationcomplex bonding, shows many of the reactions typical of aromatic compound^.^-^ However, other similarly bonded compounds such as dibenzenechromitlm do not show aromatic character,sand even biscyclopentadienyltitaniutn dichloride jails t o undergo acylation under Friedel-Crafts conditions. The present investigation relates to cyclopentadienylmanganese tricarbonyl, which is a penetration complex, differing in that dissimilar ligands are bonded to the central metal atom. The parent compound I has been reported to be stable t o air, iodine in carbon tetrachloride, hydro-
--
v $
I
W
I1
gen chloride in ethanol and to treatment with maleic anhydride in boiling benzene. Further, the infrared spectrum of I is markedly similar t o that of ferrocene in regions where the cyclopentadienyl portion absorbs, and is cited as evidence for the same type of metal-to-ring bonding." The structure proposed13 for this compound might be compared to a piano stool with the ring serving as the seat and the CO groups symmetrically arranged as the legs. Our work tends to substantiate this structure insofar as we have never detected the presence of more than one molecular species in a monosubstituted cyclopentadienylmanganese tricarbonyl compound. ( 1 ) Presented in p a r t a t t h e 134th Meeting of t h e American Chemical Society in Chicago, Ill., September 10, 1958. ( 2 ) R . B. Woodward, >I, Rosenblum a n d M. C . Whiting, THISJ O U R N A L , 74, 3158 (1952). ( 3 ) A. N. Nesmeyanov, E. G. Perevalova, R . V. Golovnya and 0. A. Nesmeyanova, Pvoc. A c a d . Sci. U S S R , 97,459 (1954). ( 4 ) R . Riemschneider a n d D. H e l m , Be?., 89, 155 (1956). ( 5 ) A. N. Nesmeyanov a n d N . S. Kochetkova, Proc. A c a d . Sci., C S S R , 109, 543 (1956). (6) P. L. Pauson, Quarl. Reus., 9, 301 (1955). (7) A. N. Nesmeyanov, Proc. R o y a l SOC.( L o n d o n ) , 246, 495 (1958). ( 8 ) H. P. F r i t z a n d E. 0. Fischer, 2. Katurforsch., l2B, 67 (1957). (9) G. Wilkinson a n d J. M . Birmingham, THISJ O U R N A L , 76, 4281 (1954).
(10) E. 0. Fischer, Z . S a l w f o r s c h . , SB, 618 (1954). (11) T . S. Piper, F . A. Cotton a n d G. Wilkinson, J . I n o v g . and V i ~ c i c a rC h e v z . , 1, 105 (1955). ( 1 2 ) J. E . Brown, H . Shagiro and E. G . D e W i t t , U. S. P a t e n t 2,818,417, Dec. 31, 1957. T h i s p a t e n t describes t h e preparation and properties of methylcyclopentadienylmanganese tricarbonyl. (13) 1 2 , A. C o t t o n , A. D . Liehr a n d G. Wilkinson, J . I n o r n . a n d AYucieay C i i c i , ~, 1, 175 ( l Y 5 5 ) ,
Cyclopentadienylmanganese tricarbonyl was alkylated and acylated using aluminum chloride as a catalyst. The alkylation reactions required only catalytic quantities of aluminum chloride. For acylation, where one mole of aluminum chloride coordinates strongly with the oxygen of the resulting ketone, only slightly more than one mole of catalyst was required. Acylation of these materials was the method of choice for studying the relative reactivity since (1) only monosubstitution takes place and (2) acylation differs from alkylation in being virtually irreversible. l 4 The method whereby two compounds are permitted to conipete for a limited amount of a third substituent has been so widely used in the past as to obviate the necessity for further comment here. Suffice i t to say that in order for valid conclusions to be drawn from the products of such a reaction, AC must be incapable -4 B
+ C + AC or BC
of breakdown under the conditions of the reaction to give BC, and nice versa. The literatureI5 refers to a somewhat similar study in the chemistry of ferrocene. The acylation of I gives rise to only one isomer, but similar substitution of I1 can give rise to two positional isomers, i.e., the 2- or a-position and the 3- or /?-position.L6 Thus when I1 was benzoylated, two isomers were isolated which differed by 64" in their melting points, gave differing infrared spectra and yielded 2,4dinitrophenylhydrazones possessing different melting points. The ratio of isomers was established by infrared analysis as 64:37 with the lower melting form predominating. The authors wish to refrain from assigning structure to these materials, but if the analogy to ferrocene holds true i t would be expected that the low melting form, since i t predominates, would be the p-isomer.16 The results of the competitive acylations are summarized in Table I. It has been reportedL6previously that when one mole of ferrocene and ten moles of anisole in chloroform solution were allowed to compete for a limited (14) R. C. Fuson, "Advanced Organic Chemistry," John Wiley and Sons, I n c . , Xew York, N . Y . , 1950 p. 338. (15) G. D . Broadhead, J . hf. Ogersby and P . L. Pauson, J . Ciient. Soc., 650 (1958). (16) K. L. R i n e h a r t , J r . , 1;.I,. Motz and Sung Rloon, THISJ O U R S A L , 79, 274Y (1957).
2090 TABLE I COMPETITIVE .4CYLATIONS C i m p e t i n g reactants (moles)
I(0.25) Benzene ( 1 . 2 5 )
Substituent (mole)
CHiC ( 0 . 2 5 )
I!
I'roducts, Yl
a
1"
51.4 9.3
0 I(O.3) I1 (0.3) I1 ( 0 . 3 ) Xnisolcc ( 0 . 6 )
CsH:,C ( 0 . 3 )
I1
31 zk 2 ti8 i i h
'I
90. y'1
0 C&C ( 0 . 3 )
..
0 Yield based on tlie nuiiiber of moles o f substituent, Tutal yield of two isomers; ruughly in the saiiie r:ttiu its obtai~ied when I1 was acylated aloiie. c Xuisole wab chosen because it is reported t o acylate only in tlie p-posit i o ~ i . ' ~ p-Methoxybenzophcnone.
aniount of acetyl chloride-aluminum chloride complex, only acetylferrocene was formed. Thus the series, in order of decreasing reactivity, becomes ferrocene > anisole > I1 > I > benzene. Alkylation of I and I1 proceeds more sluggishly than does acylation and determination of products is complicated by polysubstitution. Thus, dialkylation can give cy- and @-isomersand trialkylation can yield the 1,2,3- and 1,2,4-isomers. In
the niaterials which arc designated as di- and tributylated derivatives of I, the possibility exists that these may contain CsHI? groups arising as a consequence of the dimerization of isobutylene prior to reaction with I. IVe believe this to be a remote possibility and indeed we were unable to find any report in the literature which would parallel such a course of reaction. The authors do not wish to imply t h a t the structure of these materials is known unequivocally, but that the designation as butyl derivatives seenis most probable. I t has been suggestedI8 t h a t o-di-t-butylbenzencs would be very difficult to prepare. However, when dealing with cyclopentadienyl compounds the steric factors are somewhat reduced because of the increased bond angles.
Experimental' 0 Benzoylcyclopentadienylmanganese tricarbonylzo was prepared by treatment of t h e cyclopentadienyl compound I with benzoyl chloride and aluminum chloride in t h e usual Friedel-Crafts manncr. Addition of aluminum chl(iridc (8.7 g., 0.065 miile) i u small portions t o a stirred mixture of 10.2 g. (0.05 mole) of I, 7.05 g. (0.05 mole) of bcrizoyl chloride and 100 i d . of a r b o n disulfide resulted in a small rise in temperature atitl evolution of hydrogen chloride. \i'heii addition was coinplete ( c a . 30 min.) the mixture was heated to reflux for 4 hr., cooled, hydrolyzcd with cold dilute hydmchloric acid and the organic layer separated. T h e solution was cvaporatcd t o dryness, and the solid residues dissolved i n hexane and dried over calcium sulfate. Coticentration of the solution yielded 14 g. (0.0454 mole), OlyO, m.p. 69.5-i3.5'. Recrystallization from benzenepetroleum ether raised tlie m.p. t o 73.5-i4.5". (17) C. A. T h o m a s , "Anhydrous Aluminum Chloride in Organic Chemistry," Reinhold Publishing Corp., S c w York, N. Y., 1941, p. 302. (18) €1. C. Brown a n d .1 ; I,. Nelson, THISJOUKNAI., 75, 24 (1953). (I!)) Boiling points a n d melting points are uncorrected. ( 2 0 ) During preparation of this manuscript, t h e a u t h o r s learned o f I'rof. E. 0.Iiischer's report of t h e benzoylatim o f cyclvpentddienyl manganese tricarbvnyl tinder Friedel-Crafts cunditions: Meeting of t h c American Chemical Society, San Vranciscu, Calif., April, 1958.
Anal. Calctl. for ClJ-18hln04: C, 58.5; 11, 2.92; 1111, 17.8. Found: C, 58.9; H , 3.11; MI], 17.4. T h e 2,4-dinitrophenylhydra~one2~meltetl a t 22$)-230°. 2.1rzal. Calcd. for C2iH13MnX'407: hIn, 11.3. 1:ountl: M11,11.5. Competitive Acetylation of I and Benzene.-To :I stirred mkturC ( J f 51 g. (0.25 IIltJle) (If I, 97.5 g. (1.25 tllCJleS) Of benzene mid 19.7 g. (0.25 I I X J ~ of ~ ) acetyl cliliiride iii 200 nil. of carbotl disulfide wcre added 40 g. (0.31 mole) of alumiiium tricliloridc in small ~iortions. In the course of the hour required for the addition, the temperature rose t o 45". Stirring WLS continued for an hour, then the mixture was chillctl in an ice-bath atid hydrcilyzed by t h e drupwisc addition t j f a large excess of cold dilute Iiydr~iehl~iric acid. The organic lxyt'r was separated, dried by shaking with anhydrrius sotliuni carboriate and finally t h e scilvents were removed by distillation at atmosplicric prcssure. I he residues were tlistilletl a t reclucetl pressure tlirough a sinall spinning band fractionatirig colunin to give two fractions: fraction A (16.5 g.) boiling a t tcrnperaturcs u p to 1IO" at 23 mm. and fraction B (33.4 ) boiling at 104' at ca. 2 m m . The latter fraction, ac leyclopentadicii~ltnatiganese tricarbonyl, could be crystallized by dissolution in x minimum of ethcr and iso6ctaiic and then judiciously cooliug, XII.I>. 41.5-42.5 O . Anal. Calcd. for CloI-17Mii04: C, 43.8; H , 2.85; 1111, 22.4. Found: C, 49.2; 11, 2.S9; Mn, 21.9. The red 2,4-dinitrophenylhydrazone melted at 223-22.1'. . I m l . Calcd. for C1GIillhltiS407: hlii, 12.9. Found: h l n , 13.5. Examination uf the iiifrared spectrum of fraction A showed the material to contain CQ. lice (2.8 g., 0.023 mole, 9.376 of theory based on acetyl chloride) of acetophenone together with a larger percentage of unreactetl I and a small amount of t h e acetyl derivative. Benzoylation of II.-J\'hen I1 was treated with benzii3-l cliloride and aluminum chloride under conditions siniilar t o those described for the prcparation of benzoylcyclopentadienylmanganese tricarbonyl a total yield of i3.470 of benzoylatcd product was obt.ainctl. T h e product vas separated into two fractions depending on solubility in petroleum ether. T h a t which was most soluble w:ts recrystallized froin c:trbon disulfide t o a constant m.p. 53-54'. Ami. Cnlcd. for CI8HllhliiO.,: C , 50.6; 11, 3.42; M n , 17.1. Found: C, 5 9 . i ; € 1 , 3.41; A h , 16.S. T h e 2,4-dinitrophenylhydrazone fornicd most rapidly from this isomer, m.p. 198-200". i l n a l . Calcd. for CJ~lsMiiS107: hlii, 11.(I. Found : l f n , 11.3. T h e fraction least soluble in petroleum ether \vas recrystallized from i t , m.p. 11i-118°. A d . Calcd. for C I ~ H I I M n O IC, : 59.6; 13, 3.42; h,ln, 17.1. Found: C, 69.9; € 3 , 3.66; M n , 1'7.1. T h e 2,4-dinitrophenylhydrazoneof this isomer formed slowly, m.p. 210-211". Anal. Calcd. for C2?H1~hliiK407:hln, 11.0. Found: M n , 11.3. Examination of the iiifrared spectrum of the original tienzoylated products, prior t o separation, indicates the ratio of tlic two isomers t o be about 6 4 : 3 i with the lower melting isomer predoininatiiig. Competitive Benzoylation of I and 11.-To a solution coiltaiiiing 61.2 g. (0.3 mole) nf I , (i5.4 g. (0.3 mole) of I1 aud 42.3 g. (0.3 mole) of benzoyl cliloride i n 400 ml. o f carbon disulfide was added 52.2 g. (0.39 mole) of aluminum trichloride in sinall portions. Addition required one hour, and stirring was continued for a n additional 2 hours. Standard procedures were uscd for the work-up of the products. The residues remaining after removal of solvents were fractionally distilled through a Nester spinning band column. The forecut boiling in the range 74-86' a t 3-4 mm. amounted t o 51 g. and analysis, using vapor-phase chromatography, showed tliis material t o be iG70(38.8 8 . ) I and 24% (12.2 g.) 11. The main fraction, b.p. 174-176' at 2-3 i t l n ~ . , weighed
,.
(21) All 2 , 1 - d i n i t r o l , l i e n , l l i ~ ~ r ~ i z , , iwere i ~ s prepared h y t h e method ricscribed by I
