CA1265151A - Organolanthanide catalysts - Google Patents

Abstract

Abstract of the Disclosure The reaction of the organolanthanide complexes [ n 5-(CH3)5C5]2MCl?Li((C2H5)2O)?, M = La, Nd, Sm, Lu, with LiCH[Si(CH3)3]2 provides a straight-forward route to ether-free and halide- free bis(pentamethylcyclopenta-dienyl) lanthanide alkyls, ( n 5(CH3)5C5)2MCH-[Si(CH3)3]2.
The ( n 5(CH3)5C5)2NdCH[Si(CH3)3]2 complexes react with H2 under mild conditions to yield the corresponding hydrides [( n 5(CH3)5C5)2MH]2. These complexes have been found to be extremely active homogeneous olefin polymeri-zation catalysts, as well as catalysts for olefin and acetylene hydrogenation.

Description

s~

ORGAN~LANTHANIDE CATALYSTS

This application relates t~ eatalyst~ and more particularly ~o a method for qynthesizing organolantha-nide catalysts~ the catalysts themselve~, and methods for u~e of such catalysts.

Background of the Inventlon Much of the recent development of early transi-tion and f-element hydroearbyl and hydride chemistry can be attributed to the beneficial characteristics of bis-(pentamethylcyclopentadienyl), [ n 5(CH3~5C5]2 (herein-after Cp~) qupporting ligation. However, in studies of isoelectronic, i~oleptic 4f~f systems, it appear~ that synthesis routes ~o lanthanide Cp~MR and (Cp~MH~2 com-plexes were circuitous for late lanthanides and unknown for early (La-Nd~ lanthanides. The latter appear of greatest interest since U(III)6 and ~d(lII~5 are isoelec-tronic, because the early organ~lanthanides have the greatest importance in catalysis, and because, a priori, the early lanthanides might, for a given ligand array, offer the greatest degree of coordinative unsaturation and possibly reaciivity. In addition, the early lantha-nides are easily available and inexpensive. In planning syntheses, the use of highly lipophilic, sterically bulky R functionalities was anticipated so tha~ undesirable coordination to the lanthanide ion of ether or halide li~ands (normally present during the preparation of Cp2MR
complexes) eould be avoided. In most d-element hydrocar-byl syntheses, the choice of R is also frequently dicta-ted by the desire to avoid destabilizing ~-hydrogen ~toms. However~ it now appears that ~-alkyl elimi-nation (e.g. eq.(1)~ may be an equally important C3 C~ H3C---C~ I 3 C

/

.

decomposition pathwav ror some or~ano-~-element comolexes and must also be considered in li~and sel~ction.
Bulky ligands such as C~l~Si(C~3~3~2~ herein after (CHTMS2), orfer both t~e attraction Or su~stantial lipophilic bulk, a lack of -hydro~en atoms, as well as a defense (heretofore largelY UnaDpreCiate~) a~ainst alkyl elimination since such an elimination process woul~
produce a relatively hi~h energv Si=C bond ~e.~., eq.~2)). In the present invention, this ligan~ is C~Si~ H3C~ Si- l~3 Si ~-C~ ~ ~ ~ M-- p~---~ M
I~
employed to straight-forwardly sYnthesize a broa~ class of stable Cp~MR comp~exes rangin~ from the li~test (~ =
La) to the heaviest (M = Lu~ lanthanide. ~ther bulkv li~ands such as the mesitylene li~and afford similar properties. '~ith bot~ liganAs, hvclro~enolysis is shown to readily yield the correspondin~ series o~ hv~ride dimers, (C~H~2 for M = La to ~u. T~e rather extra-ordinary reactivltv o~ these molecules is demonstrate~
herein by their very ~ activity in ole~in oli~omeriza-tion and 301ymerization. Also s~own is the surDrisin~lv high activity of the catalysts o~ the su~ject invention for olefin hydrogenati~n.
Mec~anistically? homo~eneous olefin hydroFena-tion catalysiq with early transition metal, lanthanide, and actinide catalysts is not well understoodg and of~ers a muoh di~ferent mechanistic situation than conventional Group VIII or late transition element catalysts. In particular, the metal center mav be in a relativelv hi~h (~3) formal oxidation state, andfor it mav not DOSSeSS
energetically accessible ~ormal oxidation states for 5~

oxidative addition/reductive elimination processes, and~or it may be engaged in relatlvely polar metal-ligand bonding with a strong pre~erence for "hard" ligands (not olefins), and may exhibit unusual M H/M-C bond disruption enthalpy relationships vis-a-vis middle and late transi-tion elements. Lanthanide ions represent the extreme cases of many of the above con~iderations, and as such can offer an opportunity to better understand hydrogena-tion catalysis in such environments.

Summary of the Invention ___ ~ _ ___ Therefore, an ob~ect of the subject inven~ion is the synthesis of lanthanide catalysts for use in poly-merization and hydrogenation reactions.
Another object of the ~ubject invention is a shelf-stable environmentally acceptable lanthanide cata-lyst and an intermediate for generating a lanthanide catalyst for use in a method for the polymerization of olefins and cycloalkenes.
-A further object of the subject invention is a shelf stable and environmentally acceptable lanthanide catalyst and an intermediate for generating such a lan-thanide catalyst for use in a method for the hydrogena-tion of olefins.
These and other objects are attained in accor-dance with the present invention wherein the reaction of ( n 5-(CH3)5C5)2MC12Li((C2H5~20)2 with LiCH~Si(CH3~3~2, yields the early lanthanide alkyl t n -(CH3~5C5)2MCH[Si(CH3)3~2, (hereinafter Cp2MCHTMS2) and the reaetion of ( n 5-(CH3)5c5)2MC12Li((C2H5)20)+2 with 2-lithium-mesitylene to yield the early lanthanide aryl 2-[( n 5(CH3)5C5)2M]_mesitylene; where M - a Lantha-nide Series element, i.e., La, Ce7 Pr, Nd, Pm, Sm, Ea, Gd, Tb, Dy, Ho, Er, Tm, Yb a~d Lu. Such lanthanide alkvl eomplexes may simplistically be drawn as:

~Cp Cp' Cp' M M
(CH3)3Si I H CH3` ~ ~CH3 (CH3)3 CH3 These ether~ and halide-free bis~pentamethylcyclopenta-dienyl~ lanthanide alkyls and aryls are relatively stable intermediates which may then be stirred under a hydrogen atmOsphere~ ~o form ~( n 5(C~3~scs~2MH]2 (hereinaft (Cp2MH)2, (where M = a Lanthanide Series element as set forth above) which has been found to be an efficient and highly active catalyst for use in olefin and cycloalkene polymerization~ and vlefin and acetylene hydrogenation.
These lanthanide alkyls have the beneficial properties of having low toxicity and being otherwise envir~nmentally unobJectionable.

Detailed Description of the Invention Maierials and Methods. All operations were __ __ ~
performed with rigorous exclusion of oxygen and moisture in flamed Schlenk-type glassware in a dual manifold Schlenk line or interfaced to a high vacuum (10-5 torr) system~ or in a nitrogen filled glovebox with a high capacity atmosphere recirculator. Argon, ethylene, pro-pylene~ dihydrogen, and deuterium gas were purified by passage through a supported MnO oxygen removal column and a molecular sieve column. Aliphatic hydrocarbon solvents were pretreated with conc. H2S04, KMnO4 solution, MgS04, and ~a + 4A molecular sieves. All reaction solvents were distilled from Na/K/benzophenone under nitrogen and were condensed and s~ored in vacuo in bulbs on the vacuum line containing a small amount of [Ti( n 5-C5H5)2Cl~2ZnCl2 as indicator. Cyclohexane and heptane were additionally vacuum transferred onto Na/K and stirred for at least a day before u~e in catalytic experiments. The olefins, all hexenes, and cyclohexene were purified by siirring ~;26~

over Na/K for at lea~t 6 ~ours and ~ere freshlv vacuum transferred. Deuterated solvents were dried over ~a/K
alloy and vacuum transferred before use.
Anhydrous lanthanide halide~ were ~reDared from - the correspondin~ oxide and ammonium chloride. Pent~-methylc~vclo~entadiene was prepared bv t~e ~roce~ure set forth in Organometallics, 1984, ~, 81~-821. The com-plexe~ Cp~NdC12Li((C2H5)20)~ and Co~LuC12Li((C~)20~2 were preDared as known in the art. ~is(trimethvlsilvl?-meth~llit~ium (LiCHTM~2) and 2 lithium-mesitylene were also prepared a~ known in t~e art.

Catalyst S~yntheses In general, CP~C~T~2 and 2-(cD~mesitylene may be prepared by mixin~ ar~proximatelY equimolar amounts of Cp~MC12Li(C2Hs)20~ and LiC~T~S2 or 2-lithium-~esitvlene, as appropriate, in toluene for 8-16 hours (~referablv 12 hours) at -10C to 25C (~referably 0C). The solvent is then removed and the residue extracted with anot~er sol-vent, preferably pentane. The extract is cooled to recrystallize the Cp~cHT~s2 or 2-(cD~!mesitvlene-Exam~le 1 : CD~C1~Li 5 ~C~ 20~. A susr)ension of 2~1 (8.6 mmol) anhydrous LaC13 and 2r44 ~ (17~2 mmol) LiCr~
in 120 ml T~F was re~luxed for 12 ~ours at 0C. T~e solvent was then removed in vacuo, hein~ careful to keeD
the temperature below 10C to avoid formation o~ a less reactive complex (probabl~ (Cp~LaCl)2~ T~e w~ite resi-due was then extracted with 200 mT. diet~vl et~er, t~e mixture Piltered, reduced in volume to 30 mL, and slow~v cooled to -30C. Decantation of t~e solvent and drvin~
under high vacuum yielded 2.7 g (49 4~) Or CP~LaC12 Li((C2H~20)~ as a white, microcrvstalline sol-id. Additional product can be obtained from the mot~er liquor.

EX~pl e ?
Cp~LaCHTMS2. A su~pension of 2.6 g (4.11 mmol) Cp2LaCl2Li((C2H5~20)2 and 0.68 g ~4.1 mmol) LiCHTMS2 in 150 mL toluene was stirred for 12 hours at ODC. The solvent was then removed in vacuo and the white residue . _ extracted with 100 mL pentane. The re~ulting mixture was then filtered, the volume of the filtrate reduced to 30 mL, and the filtrate slowly cooled to -30C. Pale yellow crystal3 of Cp2LaCHTMS2 were isolated by decantation and subsequent vacuum drying. Yield: 1.4 g (60~).

.~
Cp~NdCHTMS~. The above procedure set forth in Examples 1 and 2 was repeated with 5.1 g (8.0 mmol) Cp2NdCl2 Li((C2H5)20)2 and 1.32 g (8.0 mmol) LiCHTMS2 in 50 mL toluene to yield, after work-up and recrystalliza-tion from pentane9 3.67 g (80~) of Cp~NdCHTMS2 as blue-green crystals.

Example 4 _ C~SmCHTMS ~ ~ procedure). A mixture of _ ____ _ ____ . __ 1.00 g (3.90 mmol) SmCl3 and 1.11 g (7.79 mmol~ LiCp' was refluxed in 50 ~L THF for 8 hours at 0C. The solvent was then removed in vacuo and the residue, together with 0.65 g (3.94 mmol) LiCHTMS2, was suspended in 50 mL
toluene at -78C. The mixture was allowed to gradually warm to room temperature over the next 12 hours, the solvent removed under high vacuum, and the residue extracted with 50 mL pentane~ Subsequent filtration, slow cooling of the filtrate to -780C, filtration and drying produced 0.600 g (27%) of Cp2SmCHTMS2 as red-brown crystals. An additional 0~400 g (18X) of product can be recovered from the mother liquor (total yield = 45~).

~2~S~

Example 5 Cp~LuCHTMS2. The aforementioned procedure set forth in Example 4 for Cp2LaCHTMS2 was carried out with 3.1 g (4.62 mmol) Cp~LuCl2Li((C2H5)20)2 and 0.79 g (4.7 mmol) LiCHTMS2 in 150 mL of toluene. The standard work-up and pentane recrystallization yielded 1~8 g (64~) of Cp2LuCHTMS2 as colorless crystals.

(Cp2MH)2 compounds may be prepared by stirring Cp2MCHTMS2/pentane or 2-(Cp2M)mesitylene/pentane under a hydrogen atmosphere for 0.1-1.5 hours (preferably 2 hours) at a temperature of -10C to 10C (preferably 0C). The resulting precipitate may be isolated by fil-tra~ion, washing and the like.

Exame~e 6 (C ~ . Cp2LaCHTMS2 (0.200 g, 0.35 mmol) _ was stirred under and H2 atmosphere in 50 mL of pentane for 2 hours at O~C. The resulting colorless precipitate was isolated by filtration, washed with 2x3 mL pentane, and dried in vacuo to yield 0.14 g (98~) (Cp2LaH)2 as a _____ _ colorless, microcrystalline solid.

E mple 7 (CE~N ~ . The above procedure set forth in Example 6 was carried out ~ith 1.00 g (1.74 mmol) Cp2NdCHTMS2 in 50 mL pentane. Filtration, washing, and drying yield-ed 0:.600 g (83%~ of (Cp2NdH)2 as a blue-green, microcrys-talline powder.

Example 8 _C ~ m ~ . This compound was prepared from Cp2SmCHTMS2 using the procedure above ~or (Cp2LaH)2 set for~h in Example 6 and was isolated a~ a pink-powder.

~26~

~ le3 9 _C ~ . Thi~ complex was prepared by the aforementioned procedure for tCp2LaH32 as set forth in Example 6 using H2 in pentane. The yield of (Cp2LuH)2 was 98~ colorle~s, polycrystalline solid.

Example 10 ~ Nd( n 3 C ~. A solution of Cp2NdCHTMS2 (1.00 g, 1.74 mmol) in 50 mL pentane was stirred over-night under an H2 atmosphere at 0C. The resulting pre-cipitate of (Cp2NdH)2 was filtered off and washed well with cold pentane. The hydride was then suspended in 50 mL pentane at -78~C, and with stirring, a 3-4 molar excess of propylene was intr~duced, The suspension was slowly warmed to -15C and then stirred for 3.5 hours at this temperature (dissolution of the hydride was visible by 30C). At this time, all of the hydride had reacted (as evidenced by dissolution)~ and the excess propylene and pentane were removed ln vacuo. The residue was then redissolved in 30 mL of pentane and slowly cooled over-night to -780C. The resulting large green-brown crystals were filtered off and washed with cold pentane to yield o . 49 g ( 62% ) of Cp2Nd ( n 3-C3H5).

Olefin Pol~merization a -olefing, such as ethylene, propylene~
1-hexene and butadiene, and cycloalkenes, such as cyclo-hexene, were polymerized in a 500 mL flamed round bottom reaction fla~k attached to a high vacuum line. The flask was fitled with Mor~on-type indentations, and an orerhead mechanical stirrer (high speed stirring motor, large Teflon~ paddle). The qhaft of the stirrer could be sealed to allow high vacuum pump down. Tl~e flask was also equipped with two ~traight-bore high vacuum stop-cocks. In a typical polymerization procedure, the exter-ior connecting tube of one stopcock (ca. 10 mm in length) was sealed with a new serum cap. The reaction vessel was ~6~S~

g then pumped down for ~everal hours, back-filled with inert gas, the stopcock clo~ed, the flask re-evacuated, and a measured quantity of solvent (cyclohexane or hep-tane) vacuum transferred into the reaction flask from Na/K. Next, gaseous ethylene or propylene wa~ admitted to the vessel through the gas purification column. The gas pressure was continuously maintained at approximately 1.0 atm with a mercury manometer apparatus and the tem-perature maintained at approximately -780C to +80~C.
Rapid stirring of the solutio~ was initiated, and after several minutes (to allow saturation of the solvent with olefin), the stopcock was opened and a small aliquot of approximately 5.0 mM catalyst solution of Cp'MR or (Cp'MH)2 (where M = La, Nd or Sm) in cyclohexane was injected by gas-tight syringe just abo~e the rapidly stirring solution (the syringe needle had been flattened so that the catalyst ~olution exited in a fine spray).
In the case of ethylene, voluminous quantities of poly-ethylene generally ~ormed within ~econds. After a mea-sured time interval, the polymerization was then quenched by injecting methanol through the serum cap of the second stopcock. The polymeric product was collected by filtra-tion, washed with methanol, and dried under high vac-uum. Identical resulis were obtained using ~oluene as the reaction solvent.
For 1-hexene/ethylene copolymerizations, ethy-lene gas was admitted at various pressures to a stirring Yolution of the catalyst in with another appropriate ~ -olefin, such as 1-hexene or 1-butene. Quenching of the polymerizatioQ and product isolation were as deAcribed for polyethylene.

Olefin Dimerization Example 11 _ ___ __ _ Reactions with 1 Hexene. U~ing high vacuum _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ techniques7 approximately 0.25 mmol of ~Cp2NdH)2 or ~Cp2LaH)2 was reacted with an approximately 10-fold excess of s~

_ 10 -1-hexene in 10 mL of pentane. The reactlon was begun at approximately -780C and was brought to approximately ~10C over a period of 2-3 hours. A~ter several ~ddi-tional hours at -10C, the hydride had dis~olved. The solvent and other volatiles were then removed under high vacuum and the residue dissolved in cyclohexane. The resulting solution was filtered.
The 1-hexene dimer was prepared by slowly stir-ring 50 mg of the appropriate (Cp2MH~2 complex with 3.0 mL o~ 1-hexene under 1 atm of H2 for 1 hour. After this cime, hexane was removed in vacuo at room temperature and the remaining liquid was vacuum transferred using a heat gun. GC~MS showed it to comprise about 99~ C12H26 with about 1~ higher oligomers. The total yield of oligomers was approximately 10%.

Example 12 Reaction with Butadiene Using the same proce-dure as in Example 11 for 1-hexene above, (Cp2LaH)2 was reacted with an approximately 10-fold excess of butadiene in peniane, and the product taken up in cyclohexane.

Reactions with Cy lohexene. Using the proce-dure described above in Example 11 for 1-hexene, cyclo-hexene was reacted with (Cp2NdH)2 and (Cp2LaH)2.
All of the above polymerization and dimeriza-tion chemistry was carried out under rigorously anaero-bic9 moisture free, high vacuum line conditions. At room temperature and one atmosphere ethylene pressure, the Cp~MCHTMS2 complexes (M _ La, Nd, and Sm) failed to react with ethylene over the course of several hours. Although the absence of migratory insertlon may be explained on steric grounds, it should be noted that the same complex-es undergo rapid M-CHTMS2 bond hydrogenolysis and migra-tory C0 insertion. In contrast to the Cp~MCHTMS2 com-plexes, the corresponding (Cp2MH)2 complexes undergo extremely rapid reaction with ethylene at room tempera-ture to produce voluminous quantities of polyethylene within seconds of contacting the two reagents.
Data pertaining to the polymerization experi-ment~ are set out in Table I. A number of points are noteworthy. First, it is evident that chain propagation is extremely rapid. The order of reactivity follows decreasing ionic radius: La > Nd > Lu. Furthermore, the early lanthanide sysiems display maximum activities com-parable to or in excess of those reported for the most active "homogeneous" ethylene polymerization catalysts currently known as well as those for most heterogeneous organometallic molecule/inorganic support systems.
Indeed, (Cp2MH)2 activities appear to approach those of heterogeneous "third generation" Ziegler-Natta cata-ly~ts. These organolanthanide hydride compounds also exhibit measurable activity even at -78~C. The (Cp2MH)2/ethylene turnover frequencies and catalyst effi-ciencies were estimated by quenching the polymerization reaction after measured time intervals and weighing the quantity of polyethylene produced. As such, these esti-mates are clearly lower limits to the reactivities of the most active catalysts and evidence for both reactor and microscopic mass transport effects is clear from the entries in Table I. Thus, when identical reaction proce-dures are carried out with increasing quantities of cata-lyst at identical overall concentrations, the apparent turnover frequency and catalyst efficiency falls, impli-cating inadequate monomer delivery to the reacting spe-cies (and showing that "poisoning" effects of residual air, water9 impurities, etc. may not be significant, i~e., very little of the catalyst serves a sacrificial role)~ For the less active (Cp2LuH)2 cataly~t, the turn-over frequency i5 relatively insensitive to catalyst concentration, quantity and reaction times (Table I).
~esides the obvious effect of ~tirr~ng inef~iciency, the heterogeneous nature o~ the reaction environment due to s~ -o o o o i~ c~ ~ c ~

O ~ ~ ~ ~, eo ~ X --K ~

p~ ~ X ~ ~ O

~ CO O ~ ~D a~
e ~, ~J ~
_1 e o o o ~ ~ ~ o ~ 9 0 c~ O u~
U ~5 ~t7 0 C) O ) ~ O ~ C ~ ~ ~ o o~ ~ 3 O x E ;:: O O C O O O O r~ O ~ o ~ ~ ~ t` ~ C:
X

o u~ c: o u~ V ~ ~ ~ ~ ~ U
. U

~ e N ~ r o O O ~ ~ D ~ u~ ~ O ~

~ ~ CJ
5 ~ e 3 o o ~ .. ~

~ U

653l~l the precipitation of polyethylene as the reaction pro-ceeds is no doubt a contributor to microscopic mass tran~port effects. That the most active La and Nd cata-lysts exhibit a general pattern of falling turnover fre-quency and catalyst efficiency with increasing reaction time (entries 1 and 2; 5 and 6~ suggests that diffusion of ethylene to the entrained catalytic cènters becomes increasingly difficult as solid polymer accumulates. The general pattern of decreasing e~ficiency with increasing catalyst concentration are also possibly mass transport related. Hydride dimer dissociation equilibria (which should scale as ~M]1/2) should only affect the initiation raie (rather than propagation). Although no quantitative information on the relationship of these rates is avail-able, the molecular weight distribution data and the observation that unhindered olefins react extremely rap-idly with the hydrides argue that initiation rates must be comparable to or greater than those ~or propagation.
In regard to heating effects, the dilute conditions and short reaction times do not result in significant changes in the temperature of the bulk reaction mixtures. It is, however, more difficult to rule out the importance of "local 91l heterogeneity-related effects, although ii is not readily apparent how modest local heating would diminish turnover frequencies.
For a completely homogeneous, kinetically well~
behaved (propagation as described by kp remains constant throughout the polymerization), irreversible polymeriza-tion in which termination (described by kt), chain trans-fer (described by kCt)~ and poisoning are insignificant and in which initiation is instantaneous, a Poisson mole-cular weight distribution is expected for high degrees of polymerization. That i~, the polymer (a "living poly-mer") should be virtually monodigperse, i.e., Mw/Mn =
1Ø Under similar constraints but admitting the opera-bilily of termination and chain transfer ~and assuming kp, kt, and kCt remain constant throughout the polymeri-zation? the "most probable" molecular weight distribution is expected, i.e., MW~Mn = 2.0~ We suspect that the living polymer regime is operative for the present sys-tems, modified principally by possible ma~ transport and heterogeneity effects. In regard to irreversibility, the polymerization is far from thermoneutral ( ~ H ~ -26 kcal/mol) and, with reference to termination/chain trans-fer processes, thermochemical data and experiments with 1-hexene argue that ~ -hydride elimination (eq.(3)) should be:

MCH2CH2P = MH + CH2~CHP (3 Such an elimination would be quite endothermic for a straight-chain primary alkyl. The operability of other terminacion (e~g.~ Cp'H atom abstraction), chain transfer or impurity-relaced processes is more difficult to assess.

~olym ri ions As known in the art~ the Cp2M coordination sphere is apparently too constricted to support the rapid polymerization of olefins bulkier than ethylene (few hom~geneous catalysts are known to be effective). How-ever9 we have found that ~ -olefins, such as 1-hexene~
propylene, butadiene, 1-butene and the like, can be copolymerized with ethylene by stirring solutions of (Cp2MH)2, such as (Cp2NdH)2 under an ethylene atmosphere at various pressuresO This process presumably involves ethylene at the insertion step. It was also found that Cp2Nd( n3-allyl) was effective in initiating ethylene polymerization. Such a process is likely to involve the monohapto form of the allyl (eq. (4)).

M~G~ M~-~G~ etc. (43 Olefin_Hyd~ enation _ __ Rapidly stirring any of the (Cp2MH)2 complexes with 1-hexene under 1 atm of H2 reveals that they are extremely active hydrogenallon catalysts (Nt values are as high as 120,000~hour). The mechanistic details of the catalytic hydrogenation chemistry are9 briefly stated:
(i) addiiion of metal hydride to olefin to produce a hexyl complex and (ii) hydrogenolysis o~ the metal-carbon bond to yield alkane (hexane) and to regenerate the metal hydride.
All of the following examples were performed under rigorously anhydrous and anaerobic conditions employing the procedures, methods, and precautions described previously. Solvents were purified and dis-tilled as set forth above, were stored (with stirring) over Na/K, and were vacuum transferred from Na/K immedi-ately prior to use. The olefins 1-hexene, cyclohexene, trans-2-hexene, trans-3-hexene9 and cis-2-hexene were dried by stirring over Na/K for at least 6 hours and were fre~hly vacuum transferred~ The acetylene 3-hexyne was dried by repeated vacuum transfer onto freshly activated molecular sieves followed by vacuum transfer onto Na/K, stirring for about 1 hour, vacuum transferring, and repeated freeze-thaw degassing. Purity of the final fraction was verified by GC. Hydrogen, argon, and deu-t~rium were purified by passing sequentially through regularly activated MnO, and 4A molecular sieve col-umns. Organolanthanide complexes were prepared as set forth above.

Exam ~
An oven-dried reaction vessel equipped with three burettes for the catalyst solution, the solvent, and the olefin, respectively, was attached to the vacuum line while ~till hot, pumped down for at lea~t 1 hour, clo~ed under vacuum, and taken into a glove box with a high capacity recirculating system. The burettes were then filled wi~h a solution of (Cp2MH)2 or (Cp2MR) (freshly prepared on the vacuum line using calibrated volumetric ~essels) and 1-hexene. The reaction vessel was then filled with a measured quantity of freshly dis-tilled toluene, closed, and transferred outside to the vacuum line. The reaction volume was evacuated and the solvent freeze-thaw degassed~ back-filling repeatedly with H2. Next, the thermostatted water circulating sys-tem was connected and actuated. After all parts of the system had been given appropriate time to reach thermal equilibrium and equilibrium with the reactor atmosphere, measured volumes of catalyst solution and olefin were added to the reaction vessel. High speed vortex mixing was then initiated and the H2 pressure recorded as a function of time. Appropriate corrections in data analy-sis were made for solvent and reactant~product vapor pressures. In general, conditions were adjusted such that al7 of the olefin was consumed in 0.13-1~ minutes and the overall pressure drop in the system was always less than 2% (usually less than 1%). The hydrogenation of 1-hexene in the above manner by the members of the organolanthanide catalysts of the sub~ect invention was found to be extremely rapid. In both series, the rela-tive ordering of activities was found to be approximately inver~ely proportional to metal ionic radius: Lu > Sm >
Nd > La.

Exam ~
Cyclohexene was hydrogenated using the proce-dure of Example 14 with (Cp2MH2)2 ~olution used as cata-lyst for M _ La, ~d, Sm and Lu.
In general the trends in activity observed for cyclohexene hydrogenation parallel ionic radius, i.e., La > Nd > Sm > Lu (excepting anomalous (Cp2LuH)2). This is opposite the trend for 1-hexene hydrogenation.

Exa ~
3-hexyne was hydrogenated according to the procedure of ExaMple 14, utilizing (Cp2MH)2 with M = La, ~d, Sm and Lu. As monitored manometrically and by GC/MS, the hydrogenation for all M elements proceeds slowly (relatively) until essentially all of the 3-hexyne is converted to cis-3-hexene (eq. (5)~ at which point the rate of gas uptake accelerates by a factor of about 10.

Cli3CH2C-CCH2CN3 + H2 ~ ~ C~
H

The relative raies for the first stage are Lu > Sm > Nd >
La.
The second stage of 3-hexyne reduction, conver-sion of cis-3-hexene to n-hexane, is considerably more rapid ~han the first. Although approximate rate data could be extracted from the hexyne - > hexene - >
hexane data, kine~ic orderings were more conveniently and accurately determined from independent experiments with cis-3-hexene .

Exam ro~enation of Other Hexenes _____ _ ________ ____ ___ Other hydrogenation reactions were also carried out with _ans-2-hexene, trans-3-hexene, and cis-2-hexene using (Cp2MH)2 catalysts ~ccording to the procedure of Example 14. For trans-2-hexene, the activity trend Lu >
Sm > Nd > La parallels tnat observed for 1-hexene. In these reactions, it was ob~erved that the relative activ-ities trans-3-hexene > 1-hexene > tran~-2-hexene are .
obeyed. For both Nd and Lu, the relative hydrogenation rates observed were cis-2-hexene > cis-3-hexene > cyclo-hexene.

Hydrogenation f Other Olefins Several exploratory experiments were conducted with other olefins. It was found that tetramethylethy-lene could noc be hydrogenated by any of the present catalysts at a measurable rate (259C, 1 at H2 pres-sure). In a single experiment, neat r-(+) limonene was hydrogenated largely at the terminal C=C bond in 1.5 hours. Presumably the regio- and stereoselectivity of this type of reaction could be modified by varying the reaction time or conditions (e.g., H2 pressure, addition of THF).

Heterogeneous Catalysis _______ ~ _ In addition to the homogeneous catalytic pro-cesses described above, heterogeneous catalytic processes are envisioned as being within the scope of the subject invention as well, In such a heterogeneous process, the (Cp2MH)2 would be adsorbed on the surface of a suitable inorganic substrate such as silica, silica gel, alumina, magnesium chloride, magnesium oxide or the like~ and placed in contact with ~he reaetants for polymerization or hydrogenation, as desired.

The synthetic chemistry presented here offers straightforward, general routes to a broad family of new etherfreP) halide-free bis(pentame~hylcyclopentadienyl) lanthanide alkyls and hydrides. The hydrides are of course greatly desirable synthetic targats for catalytic studies, but are equally valuable precursors for numerous ~s~

- l9 -types of ether-free~ halide-free lanthanide hydrocarbyls and other derivatives. One result of this work is thus a readily accessiblet homologous series of tractable, ther-mally stable, very electrophilic and very highly reactive lanthanide alkyl/hydride pairs which span the 4f block from the lightest (4f) to heaviest member t4f14). In chemistry involving olefins, significant reactivity dif-ferences are observed between light (La, Nd) and heavy (Lu) lanthanides. For example, the light members appear to be the mosc active homogeneous ethylene polymerization catalyscs prepared to date.
By the hydrogenation examples set forth above, it can be seen that the organolanthanide (Cp2MH)2 appears to be one of the more active homogeneous olefin hydrogen-ation catalysts yet discovered. There is no evidence that oxidative addition/reductive elimination sequences are involved in the catalysts, but rather a close coup-ling of olefin/ hydride insertion (eq. (6)) M
M-H + ~C~C~ ~ H = ~ 6".

~C~ H_C~ H~ ~
+ H2 = M.. C~ + ~ (7) S- S~ H
followed by "four-center" hydrogenolysis (eq. (7)), drawn arbitrarily in an eclipsed conformation).
While che invention has been described with reference to a preferred embodiment, it will be under-stood by those skilled in the art that various changes may be made and equivalents may be substituted for ele-ments thereof without departing from ~he scope of the invention. In addition, many modifications may be made ~.Z~5~

to adapt a particular situation or material to the teach-ings of the invention without departing ~rom the essen-~ial scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this inveniion, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims (29)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An organolanthanide of the formula [ n 5-(CH3)5C5]2MR where M is selected from the group consist-ing of the Lanthanide Series elements, and R is a group selected from mesitylene and -CH[Si(CH3)3]2.

2. The lanthanide alkyl of the formula [ n 5-(CH3)5C5]2MCH[Si(CH3)3]2 wherein M is selected from the group consisting of the Lanthanide Series elements.

3. The lanthanide alkyl of Claim 2 wherein M
is selected from the group consisting of La, Nd, Sm and Lu.

4. An organolanthanide of the formula [( n 5(CH3)5C5)2MH]2 where M is selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm.

5. A method for preparing (Cp?MH)2 comprising the steps of contacting a lanthanide compound selected from the group consisting of Cp?MCH[Si(CH)3)3]2 and 2-(Cp?M)mesitylene, with H2, wherein Cp' = n 5-(CH3)5C5 and M is selected from the group consisting of the Lan-thanide Series elements.

6. A method for the preparation of [ n 5(CH3)5C5]2MCH[Si(CH3)3]2 comprising the steps of mixing [ n 5(CH3)5C5]2MCl?Li((C2H5)2O)? with approximate-ly an equimolar amount of LiCH(Si(CH3)3)2 in a solvent, and removing said solvent, wherein M is selected from the group consisting of the lanthanide elements.

7. A method for polymerizing an .alpha. -olefin, comprising contacting said .alpha. -olefin with a catalyst under an inert atmosphere, said catalyst comprising a lanthanide catalyst of the formula (Cp?MH)2 wherein Cp' is n 5(CH3)5C5; and M is selected from the group con-sisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm.

8. The method of Claim 7 wherein said .alpha. -olefin is selected from the group consisting of ethylene, propylene, 1-hexene, butadiene and 1-butene.

9. The method of Claim 7 wherein said olefin comprises a mixture of two olefins selected from the group consisting of ethylene, propylene, 1-hexene, buta-diene and 1-butene.

10. The method of Claim 7 wherein said cata-lyst solution has a solvent selected from the group con-sisting of tetrahydrofuran, cyclohexane, and toluene.

11. The method of Claim 7 wherein said olefin is maintained in the gaseous state prior to contact with said catalyst.

12. The method of Claim 7 wherein said cata-lyst is homogeneous.

13. The method of Claim 7 wherein said cata-lyst is heterogeneous

14. The method of Claim 13 wherein said cata-lyst is adsorbed on an inorganic substrate selected from the group consisting of silica, silica gel, alumina, magnesium chloride and magnesium oxide.

15. A method for polymerizing an unsaturated monomer selected from the group consisting of .alpha. -olefins and cycloalkenes comprising the steps of dissolving said unsaturated monomer in a solvent and contacting said olefin and solvent solution with a lanthanide catalyst of the formula (Cp?MH)2 under an inert atmosphere wherein Cp' is n 5(CH3)5C5 and M is selected from the group consisting of the Lanthanide Series elements.

16. The method of Claim 15 wherein said sol-vent is selected from the group consisting of aliphatic hydrocarbons, aromatic hydrocarbons, and mixtures thereof.

17. The method of Claim 15 wherein said sol-vent is pentane.

18. The method of Claim 15 wherein M is selec-ted from the group of lanthanide elements consisting of La, Nd, and Sm.

19. The method of Claim 15 wherein said unsat-urated monomer comprises at least two monomers selected from the group consisting of .alpha. -olefins and cycloalkenes.

20. A method for polymerizing an .alpha. -olefin, comprising the steps of:
(a) evacuating a reaction vessel;
(b) adding a solvent to said reaction vessel;
(c) adding an .alpha. -olefin to said reaction vessel;
(d) maintaining pressure in said reaction vessel at approximately one atmosphere;
(e) stirring the solvent and .alpha. -olefin mix-ture rapidly for several minutes;
(f) injecting into the space above the olefin mixture a catalyst solution containing an organolantha-nide compound of the formula (Cp?MH)2 where M is a lan-thanide selected from the group consisting of: La, Ce, Pr, Nd, Pm, Sm Ea, Gd, Tb, Dy, Ho, Er and Tm;
whereby the .alpha. -olefin forms into a polymeric product which may be collected by filtration.

21. The method of Claim 20 wherein said cata-lyst solution is injected so as to form a fine spray.

22. A method for copolymerizing two .alpha. -olefins comprising the steps of dissolving said olefins in a solvent and contacting said olefin solution with a lanthanide catalyst of the formula (Cp?MH)2 wherein Cp' =
n 5(CH3)5C5 and M is selected from the group consisting of the Lanthanide Series elements.

23. The method of Claim 22 wherein said .alpha. -olefins are selected from the group consisting of ethylene, propylene, butadiene, 1-hexene, 1-butene and cyclohexene.

24. A method for hydrogenating olefins com-prising the steps of (a) filling an evacuated reaction vessel with a measured volume of solvent;
(b) preparing a substantially pure hydrogen atmosphere in said reaction vessel and over said solvent;
(c) adding measured amounts of a catalyst and an olefin, said catalyst including a lanthanide complex of the formula (Cp?MH)2, where Cp' = ( n 5(CH3)5C5) and M
is selected from the group consisting of the Lanthanide Series elements; and (d) mixing;
whereby said olefin is hydrogenated.

25. The method of Claim 24 further including the initial steps of preparing said reaction vessel to be moisture-free.

26. The method of Claim 24 wherein said sol-vent is selected from the group consisting of cyclohex-ane, toluene and tetrahydrofuran.

27. The method of Claim 24 wherein M is selec-ted from the group consisting of La, Nd, Sm and Lu.

28. A method for hydrogenating olefins com-prising the steps of:
(a) evacuating a reaction vessel;
(b) filling said evacuated reaction vessel with a measured quantity of a solvent;
(c) degassing said solvent in said reaction vessel and backfilling with hydrogen;
(d) allowing the temperature of said solvent to reach thermal equilibrium with the temperature of the hydrogen;
(e) adding a measured volume of an olefin;
(f) adding a measured volume of a catalytic solution to said reaction vessel to form a reaction mix-ture, said catalytic solution comprising a mixture of (Cp?MH)2 in a solvent, where Cp' = ( n 5(CH3)5C5) and M
is selected from the group consisting of the Lanthanide Series elements; and (g) mixing said reaction mixture, whereby said olefin is hydrogenated.

29. The method of Claim 28 wherein said sol-vent is selected from the group consisting of toluene, tetrahydrofuran and cyclohexene.