KENDELL P. LONG
5312
total amount of gas was liberated. The solid was collected under nitrogen, washed with methanol and ether, and dried. Anal. Calcd. for "i(CH2=CHCN)2: Ni, 3j.62; acrylonitrile, 64.38. Acrylonitrile was determined by careful thermal decomposition of the nickel complex in a high vacuum apparatus. The volatile fraction was weighed and identified by infrared malysis as pure acrylonitrile. Found: Ni, 35.3, 35.6; acrylonitrile, 63.3, 60.2. Preparation of the Complex of PdCl2 with Acrylonitrile.Palladium dichloride (1 9.) was dissolved in hot acrylonitrile, and the solution was filtered. Diethyl ether was added, and the solution was cooled to about -40", whereby yellow crystals appeared. The complex is not very stable and loses acrylonitrile slowly a t room temperature. Anal. Calcd. for PdC12(iYC-CH=CH2)2: P d , 37.5; C1,26.0. Found: Pd, 37.5; Q26.3. Preparation of Bis-acrylonitrile Nickel Triphenylphosphine.-Freshly prepared bis-acrylonitrile nickel (2.5 g.) was suspended under nitrogen in a solution of 4 g. of triphenylphosphine in 40 ml. of ether and was refluxed for 3 hours, The red starting material was slowly converted into a yellow powder. This was filtered, washed with ether, dnd dried under exclusion of oxygen. When heated in a sealed tube, it decomposed into acrylonitrile, triphenylphosphine and nickel a t 185'. Anal. Calcd. for Si(CH2=CHCH)2P(C6H5)3: S i , 13.75; P, 7.3; S , 6.3. Found: Ni, 13.8, 13.9; P, 7.3; N (Kjeldahl), 6.1. Preparation of Heptatrienenitrile with Bisacrylonitrile Nickel a s Catalyst.-The conditions were essentially the same as described by Cairns, et CLZ.,~ except that the bis-
[CONTRIHUTIOS FROM
THE
Vol. 81
acrylonitrile nickel was employed as catalyst. The reaction mas carried out a t 75" and 13.5 atm. and required no induction period. The resulting heptatrienenitrile boiled a t 53' (2-3 mm.). Its infrared and ultraviolet spectra were identical with those reported for heptatrienenitrile.a Anal. Calcd. for C,H,N: C, 79.97; H , 6.71; N, 13.33. Found: C, 79.92; H, 6.72; N, 13.19. Cycloactatetraene from Acetylene and Bisacrylonitrile Nickel.-Freshly prepared bisacrylonitrile nickel (1 9.) was suspended in 50 ml. of dry tetrahydrofuran and was allowed to react under the usual precaution^,^ in a stainless steel rocker bomb (500 ml.) a t 80-85' and 20.4 atm. acetylene pressure for 18 hours. The lowest boiling fractions (after filtration from a polymeric resin-like material (polyacetylene) and removal of the solvent) consisted mainly of cyclooctatetraene as evidenced by comparison of the infrared spectra with an authentic sample and vapor-phase chromatography. X small amount of a higher-boiling fraction was found to consist of a complicated mixture (vapor-phase chromatography) and was not examined further. Infrared analysis was performed on a Beckrnari IR 4 Instrument. --C-h-, Compound Acrylonitrile Ni(CHz=CHCN)? Pii:CHz=CHCN)*P(CBHs)3 PdCIz(NCCH=CHs)z
State Liquid Solid (in S u j o l ) Solid (in Nujol) Solid (in h-ujol)
em.-! 2245 2220 2180 2290
Vinyl absorption (900-
1000
cm.-I) Present Absent Absent Present
( 7 ) W. Reppe, "Neue Entwicklungen auf d e m Gebiet der Chemie des Acetylens und Kohlenoxyds." Springer, 1919, pp. 137-138.
DAYTOS'7, OHIO
RESEARCH CESTER,HERCULES POWDER Co.]
Complexes of Aluminum Chloride and Methylaluminum Dichloride with Bis(cyclopentadieny1)-titanium Dichloride as Catalysts for the Polymerization of Ethylene BY WENDELL P. LONG RECEIVED XAY4,1959 The interactions of bis-(cyc1opentadieny.l)-titaniumdichloride, ( C5H6)1TiC1z, with aluminum chloride and with rrietliylaluminum dichloride have been followed spectrophotometrically, In each case two complexes are formed, the first at a ratio of one A41per T i and the second a t a higher ratio. Only acid-catalyzed polymerization was observed with ( C5Hj)2TiC12 and aluminum chloride, whereas linear polyethylene was obtained with methylaluminum dichloride. The initial rate of polymerization paralleled the spectroscopic concentration of the first complex. The active catalyst is discussed.
X few years ago Ziegle? gave great impetus to the field of low-pressure, ordinary temperature polymerization of 1-olefins. Since his release of information there has been a heavy concentration of effort to commercialize such polymerizations ; considerable effort also has been made to explain the mechanism of this type of reaction. As ordinarily used, the Ziegler process involves activated catalyst particles dispersed in an inert medium. Activity is subject to many factors: the metals used, their valence states and ligands; the catalyst history; the temperature and pressure; and the monomer. For mechanism studies, the most difficult variable is the solid surface of the catalyst. For the present study, this problem has been avoided by the choice of a completely soluble catalyst based on bis-(cyclopentadieny1)-titanium dichloride (I), (C6HJaTiC12.
'The catalyst based on I was first reported by B r e ~ l o w . ~Xatta4 and his co-workers have used the compound and some of its derivatives in their mechanism studies. In the presence of triethylaluminum or diethylaluminum chloride, I is reduced rapidly to complexes of trivalent titanium. The high degree of catalytic activity for ethylene polymerization associated with the compound is dependent on the presence of a transitory complex of tetravalent titanium3a; the trivalent state is very much less active. Complexes of I with methylaluminum compounds are much more stable than the corresponding ethyl derivatives. For this reason, the methyl derivatives have been used for the study reported here. Information has been obtained which correlates catalyst structure with catalytic activity.
(1) Presented in p a r t before the Delaware Science Symposium, Newark, Del., F e b r u a r y 1 4 , 1959, and a t t h e Symposium on Stereospecific Polymerization a t t h e 135th National Meeting of t h e American Chemical Society, Boston, Mass., April 5-10, 1959. ( 2 ) K . Ziegler, E. Holzkamp, H. Brei1 a n d H. h f a r t i n , Aiigew. C h e w . 67, 541 (1955).
(3) (a) D. S . Breslow, Belgian P a t e n t 551,283 (19571, U. S. P a t e n t 2 , 8 2 i , 4 1 0 (1958); (b) U . S. Brcslow and X, R. Newburg. TrIIs JOURN A L , 79, 5072 (1957); 81, 81 (1959). (4) G. S a t t a , P. Pino, G. X a z z a n t i , U. Giannini, I?. Mantica and >I. Peraldo, Chiiii. e i : f d (.\fila??),39, 19 ( 1 9 5 7 ) , J . P o l y m c i Sci.. 2 6 , 120 (1957).
Oct. 20, 1959
CATALYSTS F O R POLYMERIZATION OF
5313
ETHYLENE
Experimental Materials.-Bis-(cyclopentadieny1)-titanium dichloride was prepared by the method of m'ilkinson and Birmingham.' Baker and Adamson anhydrous sublimed aluminum chloride was ball-milled in n-heptane in steel mills and used as the dispersion. Methylaluminum dichloride was prepared in n-heptane solution by addition of aluminum chloride t o trimethylaluminum obtained from Rocky Mountain Research; the analysis of four solutions, normalized to Al, was 1.00 Al, 2.01 3~ 0.08 C1, 0.99 f 0.03 CHI. Toluene was treated as described by ChienG; it was transferred by hypodermic syringe. Phillips research grade ethylene dnalyzed to be 99.96+ yG pure was used throughout. Linde Seaford grade nitrogen was used directly. Bis-( cyclopentadieny1)-methyltitaniumChloride (VI).'-Into a nitrogen-filled, 200-ml. capped Pyrex centrifuge bottle containing 5.00 g. (20 mmoles) of I was injected 10 ml. (20 mmoles) of a 2.0 [I. solution of methylmagnesium chloride in ether. The bottle was shaken overnight. After centrifugation, the liquor was removed and taken to dryness t o give 4.33 g. of crude product. The product was recrystallized from heptane and then from methylcyclohexane. The compound is stable in air a t room temperature for several weeks. Anal. Calcd. for (CaHa)2CH3TiC1: C, 57.7; H, 5.73; C1, 15.51; Ti, 20.95. Found: C , 5 7 . 3 ; H , 5.64; C1, 15.47; Ti, 20.2. Spectra.-All spectra mere taken witli Cary M14 spectrophotometer. The cells were fitted Kith a T-tube opening so that solutions could be introduced through rubber stopples with hypodermic syringes. .I steady purge of nitrogen was ~ during use. maintained through the u p p tube Interaction of Aluminum Chloride with I.-Compound I has a spectrum w t h absorptlon maxlma a t 388 and a t 515 mp, Fig. 1 (curve I ) . -4s aluminum chloride was added to
0.1
0.6
0.5
w' v 0.4
2 9
P*
0.3
0.2
0.1
0.0 41
Fig. 2.-Interaction
of 5.0 millimolar (C6H5)zTiCl~with
> 1 AlCla in toluene, 0.5-cm. cell; numbers indicate A1:Ti ratios. I n the case of aluminum chloride with I a brown flocculent precipitate slowly appeared. Spectra were taken within 3 minutes of the mixing of the components so that the precipitate would be entirely negligible. Addition of ether, even after much solid had formed, gave a clear solution with spectrum identical with I . attempts to isolate the species I1 and I11 led only to darkcolored oils. Interaction of Methylaluminum Dichloride with 1.-To 2.0 ml. of 3.0 millimolar I in a 0.5-cm. cell were added 0.030ml. portions of methylaluminum dichloride solutions in toluene. The change from the E15 mp band of I to the new peak a t 575 mp is shown in Fig. 3 (curve IV). As more methylaluminum dichloride was added, the spectrum
0. i
0.i
i z 20.2
8
9 0. i
0.1
0.5
0. (
0.4
4
mP.
Fig. 1.-Interaction
of 5.0 millimolar (CsH5)zTiClZ with numbers indicate A1:Ti
5 1.2 AICll in toluene, 0.5-cm. cell; ratios.
the 5.0 millimolar solution in toluene, a new maximum at 580 mp was produced, Fig. 1 (curve 11). The change required approximately 1.2 AI: Ti for completion. h t lower concentrations, a simultaneous change from the peak a t 388 mp to one a t 410 mp was also observed. Larger amounts of aluminum chloride gave another species having an absorption maximum a t 475 m l (Fig. 2, curve 111). ( 5 ) G. Wilkinson and J. M. Birmingham, THISJOURNAL, 76, 4281 (1954). ( 6 ) J. C . W. Chien, rbid., 81, 86 (1959). (7) I a m indebted t o Dr. S . C. MacArthur for the preparation of
this sample b y a modification of t h e procedure described by Farbwerke Hoechst A.G.8 18) German P a t e n t DAS 1,037,440 i l R 2 8 ) .
$
0.3
2
2
!I
0.2
0.1
0.0 400
500
600
700
IO
Fig. 3.--Interaction of 3.0 millimolar (C5H6)2TiCIp with CHIAIClz in toluene, 0.5-cm. cell; numbers indicate A1:Ti ratios.
