Homo and co-oligomerization of C2-C5 olefins in the presence of cluster ruthenium complexes

,.~oumal lllelal lC

Chemistry ELSEVIER

Journal of Organomelallic Chemist~, 526 (1996) 33-41

Homo and co-oligomerization of C2-C 5 olefins in the presence of cluster ruthenium complexes Mado Bianchi a, Gloria Menchi ~, Ugo Matteoli

b, Franco Piacenti

~'*

a Deparmwnt of Organic Chemistry, University oJ'Florence, Via G. Cappmti 9. 50121 Firenze, Italy b Delmrtnwnt of Chemistt3,. University of Venice, Calle Larga S. Maria 2137. 30123 Vem'zia. Italy Received 8 February 1996; revised 9 May 1996

Abstract Propene can be oligomerized using Ru3{CO)~2 as catalytic precursor in solution of a hydrogen donor solvent or in the presence of ethylene. Ethylene-propene mixtures undergo oligomerization in the presence of Ru3(CO)~2 at 120°C with conversions even higher than 80%. Higher olefins do not react in the presence of this calalytic system. Rutbenium hydrides and alkyls are suggested intermediates in this catalytic cycle. Keyword.w Oligomerization; Co-oligomerization; Ruthenium complexes; Catalysis; Olefins

i. Introduction The oligomerization of propene in the presence of Ziegler~ Naua [ 1~9] or m|nsition metal catalysts [7.10= 12], mainly Ni [6,7,13~15] based catalysts, has been reported by different authors. Even higher olefins, frorn C4 to C 8. have been subjected to this reaction to give products containing up to 30 carbon atoms [6.7,13,16~ 22]. The co-oligomerization of the above olefins in the presence of the same catalysts has also been reported [23-251. Propene and butene oligomerization and cooligomerization has in fact reached industrial relevance under the name "Dimersol Process" [26,271. We have previously studied the oligomerization of ethylene and found that Rub(CO)t2 displays a fitir cat-

" Corresponding author.

alytic activity for this reaction [28]. We have now extended our investigation on the catalytic activity of ruthenium clusters to higher olefins. C ~, C ~t. C~..'rod 1o their coooligomerization with ethylene.

2. Results The oligomerization of propene in the presence of Ru~(CO)~2, tested in different solvents (Table I). requires a minimum temperature which is higher than the one necess:a'y when using ethylene [28]. The activity of the catalytic system appears to be higher in a hydrogen donor solvent such as propan-2-ol and, surprisingly. also in cyclohexane. Dehydrogenation of a paraffin. n-heptane, in the presence of a ruthenium carbonyl carboxylate catalytic system has been observed previously [29]. The reaction rate is approximately the same in both solvents, while the regioselectivity is very different. In cyclohexane 83% of the reaction products consist of branched chain olefins (2.methyl-pentenes).

0022-3/8X/96/$15.00 Copyright © 1996 Elsevier Science S.A. All rights reserved. Pil S0022-328X(96)06464-9

34

M. BiaPIt'hiet al./ Journal of Organometallic Chemi.~try526 (1996) 33-41

Table I Oligomerization of propene in various sotvents in the presence of Ru 3(CO)tz. Catalyst precursor 0.94mmol Ru; solvent 25 ml; benzene as internal standard C ~H ~, Solvent T Reaction Cony. Reaction products (wt.%) (g) (°C} time (h) (%) C6 C9 C iz

linear 20,0

Toluene

150

20

0. I

45.1 9.0

Chlorobenzene

180

70

42.0

Cyclohexane

180

20

22.6

Propan-2-ol

150

22

6.1

Propan-2-ol

180

22

19.5

30.4

--

82.7

16.6

I O0

95.2

while in propan°2 ol they are mainly linear (95%) (Ta+ ble I). Dimers are exclusively formed in this last sol+ vent, Trimers and tetramers are formed in good yield (4~%) in ehlorobenzene when using prolonged reaction times, In order to obtain info=~ation on the ntmwe of the catalytically active spedes, we have compared the activ+ ity displayed in this reaction alternatively with

13.2

I00

83.4 10,4

31.5 75.0

69.6 17.3

13.2

54.9

55.3 25.0

7.0

2-methyipentenes

I()(3

4,8

Ru+~(CO)I2. H4Ru4(CO)I: and the residue recovered from an oligomerization experiment of ethylene per+ formed in the presence of Ru~(CO),, (Table 2). All experiments we~v.carried out in toluene. Wilt1 propene, as had been experienced with ethylene [28], hydride species seem to favour, although not to a great extent, the oligomerizatioa reaction. In both cases h o w e v e r the c o n v e r s i o n is rather low. T h e catalyst

Table 2 Ollgomeriza|ion of propene in ti~epre~nce of various catalyst precursors, Catalyst precursor 0 94mmol Ru: toluene 25m1: T 150+C; benzene as internal standard C~ H o (g)

20,0

Catalyst precursor

Ru ~(CO},,

Reaction time (hi

17

Couv, (+:+,)

0,1

Reaction products (wt.%) C~

C+~

linear 100

2-methylpentenes

45, I

54+9

IS,9

81,1

16,4

Prefol~ate "

~0

~9,0

96.9

14,0

lh~formate '~

100

33,9

94,8

I I,.~ 12.7

3.1 88,5 5.1 87.3

The catalyst was recovered in nitrogen atmosphere at 60°C and evaporated under vacuum (from 20 to 0.2 mmHg) from the ~action crude of a i~tevh~usethylene oligcm~erizaticmin the i~esence of Rn,~(CO)tz in toluene at 150°C,

M. Bianchi e~ al,/ Journal of Orgam,metallic Chemi,~try526 (1996) 33-41

recovered from a previous oligomerization experiment of ethylene, in contrast, shows a much higher activity, providing 29% conversion to be compared with 2% with H4Ru4(CO~z in the same time (around 20h). The reaction however .~eems not to p~'o.eed much further even with this catalytic system since only 34% conversion is achieved in 100h. Attempts to oligomerize but-l-ene and pent-l-erie in the presence of Rua(CO), 2 or H4Ru4(CO)Ia in chlorobenzene and toluene were also made. No oligomers were detected in the reaction medium even after prolonged heating at 180°C. When using as catalyst the residue recovered from a previous oligomerization experiment on ethylene, x~'e could however detect, working in chlorobenzene, the formation of Cs and C~z oligomers from but-l-ene with approximately 9% conversion. The above results seem to indicate that ethylene helps to transform the ruthenium carbonyl precursor into the catalytically active species for the higher olefins tested also. We have then investigated the co-oligomerization of ethylene and propene. Both the nature of the products obtained and olefin conversions would in fact provide indications of the role played by ethylene in this reaction. A first series of co-oligomerization tests on almost equimolecular mixtures of the two olefins was performed at 150°C in various solvents in the presence of Ru~(CO)~ (Table 3). The ratio of C,/C~ olefins converted increases from 1.3 to 1.8 and to 2.2 wl~en using cyclohexane, chlorobenzene or toluene respectively as

35

G

z

9;

w t:

s.

C

s:

z ,.m

[,,,,

,6

¢-4

2~

E t:

.o_

uT~_

G

li li h¢

eq e-

g

o

IiI!

e..,

~g

GI= I

I C

U

li li ¢.q

6

,o

~g

solvents.

Ethylene conversion is at least 90%, while that of pro~ae is generally lower ~50%), The reaction products are mixtures of C,,-C~0 olefins, They are due to the oligomerization of ethylene (batches and 3-methylpentenes), of propene (2omethylpcntenes) and to the co-oligomerization of the two olefins (C.s and C,~ olefins). It may be noted that in cyclohexane both ethylene and propylene conversiens are high (Table 3). The composition of the reaction products changes as the olefin conversion proceeds (Table 4). Initially, in fact, C4 are mainly tbrmed and the Cz/C.~ conversion ratio is rather high. This ratio decreases as the reaction proceeds, and significantly increasing amounts of Cs and C? olefins are formed, indicative of ethylene-propene co-oligomerization. The influence of the reaction temperature has also been investigated (Tables 4-6). The reaction starts already at 100°C in cyclobexane, while a temperature of 150°C is necessary in toluene. In aromatic solvents like benzene and toluene the conversion of ethylene reaches 90% and that of propene up to 60%. In cyclohexane, on the contrary, the conversion of propene may also exceed 80% (Table 5). In chlorobenzene higher temperatures

G ._.9.

~o

m

r~

O

M. Blare'hi et al./ Jr~urnal of Or,~anomerallic Chemistry 526 (1996) 33-,11

o

no

o~

..1 ,.0

r-"

G

w~

Ii li li I: li

8

R

i

m

I~ m

q

G~ =1

O0 m

M, Biunchi ct aL / Journal ~f Orgmu~memili¢" Chemi~u'y 526 (1996) 33-41

37

c~ .=_

Z IZ

,-3

=

~I~

L; .=_ ,=_

i. f-.

= =

li li Ii

-~

C

I=

lil!li

E

if~ ,. =

,~, ~I~.,

e-

.l=

E

0 0

E

~r

o ~ ~1~,

w

I=

~

~

<

li li li

-1

li li

E, ~s .o

E

r~

I=

m

J

~ .~ ~ ~,~

Ol=l=

~"~ i~. ~. I = 1 = I=

•~-

"il;

Iff

dd

°1

@

I=

o. I.-

N

~

N

M. Bianchi el a l . / Journal ~f Or~anometallic Chemistry 526 (199~) 33-41

~8

m

I

I

I

I

-.7="

I

I

I

I

~"

o

G

0 -~,

a.t

,-1

e.,

G w'~

,,O

o

I w~

e~

¢',4

m

Oq

li li li i

M

m

e~ ,0

o.

~g

.g: p,.. fN

¢.q

~ ~21 ~ Sl ,,Tll

~N

I!I! i

G

e,~

[

~2

e4

e~

ff

e

z G

1

G

z

~

N m

M. Bianchi el a l . / Journal o fOrganometallic Cht,miswy 526 (1996) 33-41

) o

•

t,-:

¢,..

E q~

t.,., ¢'4

¢.q g=

G e~

,,q-

39

increase the formation of higher molecular weight products (Table 6). The influence of the C2/C.~ olefin ratio on the reaction course has also been tested by changing this parameter (Table 7). Ethylene being much more reactive than propene, it is possible to convert equimolecular amounts of the two olefins only by using a very low C 2 / C 3 ratio. The obvious consequence is also a very low olefin conversion. When the C 2 / C 3 olefin ratio increases, the conversion of both olefins increases also. In fact, a reasonably higher C 2 / C 3 ratio causes an increase in the formation of the heavier products which are almost absent when the above ratio is very low. In the presence of H4Ru,,(CO)t2 (Table 8) the C2-C.a oligomerization takes place already at 100°(2 even if toluene is used as solvent. This catalytic precursor provides approximately the same results as Ru3(CO)12. The catalytic system formed by these two precursors is therefore most probably the same. The co-oligomerization of C 2 / C 5 olefins in the presence of Ru3(CO)12 may be promoted in chlorobenzene (Table 9). When the C2/C s ratio is not too high we may notice the formation of C 7, C 9 and C,0 olefins.

e.:

t5

6 " < z~

m

tS

!10

t~ f'4

°I IN

.--.

tY ,q.

k~ e~

t~

7; t~ e~

3. Discussion

q~

Triruthenium dodecacarbonyl does not promote the oligomerization of C~, C4 and C5 olefins under the conditions used for ethylene. The oligomerization of propene may be promoted using Ru~(CO))~ as catalytic precursor, working in the presence of hydrogen donors; that of butol-ene takes place only in the presence of a catalytic system recovered from a previous oligomerization of ethylene. In propan-2°ol or cyclohexane solution or in the presence of ethylene, propene may be oligomerized or co-oligomerized using Ru.~(CO)t2. An appropriate, con° tinuous source of hydrogen must be provided to this system, such as the presence of ethylene, in reagent concentration, to achieve reasonable conversions. Di° enes, C 6 and Cs, have in fact been detected when reacting ethylene in the presence of Ru~(CO)12 [28]. in the case of prol~ne too, as already suggested for ethylene [28], the intermediates involved in this reaction are very likely hydride and alkyl ruthenium carbonyls.

.9. N

e~ o

4. Experimental details ¢q

N

~D

m

GC analyses were performed on a Perkin-Elmer 8320 instrument; GC mass spectra were recorded with an liP 5970A spectrometer.

40

M. Bianchi et al. / Journal of Orgam~metallic Chemixtry 526 (1996) 33-41

4.1. Materials Ethylene, propene, but-l-ene, pent-l-ene and all reference compounds were commercial products. All solvents were purified in the usual manner [30].

4.2. Catalyst precursor Ru3(CO)I2 [31] and H4Ru4(CO)12 [32] were prepared as described in the literature.

4.3. Oligomerization experiments Propene and but-l-ene oligomerization tests were performed as described for ethylene in a previous paper [28]. In the case of pent-l-ene oligomerization, the olefin was added together with the solvent, The ethylene/propylene co-oligomerization tests were carried out in a 150ml stainless steel rocking autoclave heated in a thermostatic oil bath where the temperature could be kept at the chosen value 5:1 °C. 'Poe catalyst precursor, the solvent and benzene fintemal standard) were initially placed in the reaction ves~l under dinitrogen, and finally the required amount of propylene and then of ethylene was added. The autoclave was then heated at the chosen temperature. The reaction was stopped when required by rapidly cooling the autoclave. The residual olefins and the more volatile products were collected in a gasometer, and the liquid re,actio,a crude product in a cooled Erlenmeyer flask ( ~ $0 to ~ 80°C), Working conditions m'e reported in the table:~, Analytical procedures adopted are t'eported below.

4,4, Reouse of the ctaalyttc system

Ru~(CO),:, the solvent and ethylene were placed in the usual manner [28] in the autoclave which was then heated to 150°C for 2 h, Then the autoclave was rapidly cooled to room temperature and the liquid reaction crude recovered under dinitrogen, The liquid components were distilled gradually, lowering the pressure from 20 to 0.2 mmHg, so that the temperature should not exceed 60°C, The solid residue was recovered by addition of 25 ml solvent and transferred to the autoclave as catalyst for subsequent oligomeri~ation or co° oligomerization tests, 4,$, AnalyticM procedure The conversion of the olefins and the composition of the liquid recovered were determined as described in a [xevious p a ~ r [28], The amounts of the components were calculated using calibration curves obtained by

mixing the C4, C5, C6, C7, C8, C~, C~o, Ct~ and C~2. When necessary olefins were identified through their GC mass spectra [33]. The ratio of linear to branchedchain olefins in the C 5, C 6, C7 and Cs clusters was determined on the hydrogenated crude. All C~, C 6, C 7 and C s saturated hydrocarbons were identified by their GC mass spectra [33].

Acknowledgements We acknowledge financial support from the CNR, Progetto Finalizato Energetica and MURST.

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41

[31] G. Braca, G. Sbrana and P. Pino, C~im. ~ad. fMilc~e~:,50 (1968) 121. [32] F. Piacemi, M. Bianchi, P. Frediani and E. Benedeui, Inorg. Chem., !0 (1971) 2"/59. [33] S.R. Hellez aM G.W.:L Milne, EPA/NIH Mass Spectral Dat. Base, Vol. I, US Department of CommerLe/National Bureau of Standards, Washihgton, DC, I978.