Patent Application: US-51961806-A

Abstract:
a zwitterionic group viii transition metal complex containing the simple and relatively small 3 -- but - 1 - en - 2 - olato ligand that catalyzes the formation of polypropylene and high molecular weight polyethylene . a novel feature of this catalyst is that the active species is stabilized by a chelated olefin adduct . the present invention also provides methods of polymerizing olefin monomers using zwitterionic catalysts , particularly polypropylene and high molecular weight polyethylene .

Description:
the initiator / catalyst of the present invention is a zwitterionic ni complex containing a 3 -( arylimino )- but - 1 - en - 2 - olato ligand stabilized by a chelated olefin adduct . in particular , the present invention provides a catalyst of the following formula 1 : wherein m is a group viii transition metal such as ni , pd , pt ; r ′ is a one electron hydrocarbyl , such as methyl , ethyl , substituted or unsubstituted r ′ is → benzyl ( which is a combination of a sigma bond and a pi - bond from the bound aromatic unit ), and the like ; l ′ is a two electron ligand , such as a phosphine , amine , olefin , ether , and the like , or is a link to r ′ when r ′ is r ′ is → benzyl ; x ′ is a two electron donor , such as imine , phosphine , carbonyl , and the like ; each r , r ″, r ″′, r iv is independently hydrogen , an alkyl or a substituted or unsubstituted aryl group ; ( l ) n is a tether group , such as a series of methylene carbons , oxygen , amine , and the like , wherein n is 0 or 1 ; x ″ is a component having two electron donor functionality , such as oxygen , amine , phosphine , and the like ; la is a lewis acid , such as a trisubstituted boron , trisubstituted aluminum or a proton ; and a particularly preferred catalyst is compound 2 shown in the scheme 1 below , having the structure : preparation of the zwitterionic ni complex catalysts of this invention is exemplified by the specific reactions shown in scheme 1 : as shown in scheme 1 , synthetic access begins with 3 -( 2 , 6 - diisopropylphenylimino )- butan - 2 - one [ 24 ], which is obtained by condensation of 2 , 6 - diisopropylaniline with 2 , 3 - butanedione . deprotonation with nah in thf provides the sodium salt in 80 % yield . subsequent reaction of the salt with ni ( pme 3 ) 2 ( η 1 — ch 2 c 6 h 6 ) cl [ 25 ] provides a new compound , which contains the ligand fragment ( 1 h nmr in c 6 d 6 : 4 . 91 , 4 . 63 ppm ), an η 1 - benzyl group ( 1 h nmr : 7 . 56 ppm ) and pme 3 . single crystals of the product were obtained from a solution of pentane and the results are shown in fig1 . the product is thus ( 3 -( 2 , 6 - diisopropylphenylimino )- but - 1 - en - 2 - olato )( η 1 - benzyl )-( trimethylphosphine )- nickel ( compound 1 as shown in scheme 1 ). structural characterization of compound 1 reveals a distorted square - planar geometry with a cis relationship between the benzyl ligand and the imine nitrogen . the 3 -( 2 , 6 - diisopropylphenylimino )- but - 1 - en - 2 - olato ligand coordinates to the nickel via the nitrogen and oxygen atoms with ni — o and ni — n bond lengths of 1 . 9031 ( 16 ) and 1 . 9555 ( 18 ) å , respectively . the c1 - c2 ( 1 . 344 ( 3 ) å ) and c3 - n ( 1 . 294 ( 3 ) å ) distances are consistent with double bond character , whereas the c2 - c3 ( 1 . 486 ( 3 ) å ), c3 - c4 ( 1 . 497 ( 3 ) å ) and c2 - o ( 1 . 315 ( 3 ) å ) distances reveal single bond character . these data indicate localized bonding in the chelating ring . the addition of 2 equivalents b ( c 6 f 5 ) 3 to compound 1 in toluene results in the formation of me 3 p — b ( c 6 f 5 ) 3 , which precipitates out of solution , and a new organometallic product . 1 h nmr spectra of the product show the formation of two isomers in a 9 : 1 ratio . the upfield shift of the aromatic signals from — ch 2 c 6 h 5 from 6 . 9 to 7 . 6 to 5 . 9 to 6 . 6 ppm indicates □ 3 - coordination . the vinyl protons are observed as a pair of doublets in the range of 3 . 25 to 5 . 02 ppm . the 11 b nmr spectrum shows a signal at − 2 . 6 ppm , consistent with boron - oxygen coordination . 1 h - noe spectroscopy between the vinyl group and the benzyl group indicates that the sets of isomers arise from pseudorotamers of the benzyl ligand [ 23 ] and that the major isomer contains a cis relationship between the vinyl group and the benzyl group , as shown in scheme 1 . single crystals of compound 2 formed from a toluene solution and the structure is shown in fig2 . isomer 2 ( a ) was obtained preferentially . the oxygen binds to the lewis acidic boron and by doing so , forces coordination of the olefin to the nickel center . the distances from ni to c1 and c2 , are 2 . 109 ( 6 ) å and 2 . 455 ( 6 ) å , respectively . the rotation of the c2 - c3 bond and the c1 - c2 - c3 - n torsional angle ) ( 41 . 6 ( 8 )° optimize overlap between the π - orbital of the — c ═ ch 2 group and ni . the c2 - o distance ( 1 . 319 ( 6 ) å ) is characteristic of a single bond , while the c1 - c2 ( 1 . 371 ( 7 ) å ) distance is more indicative of a double bond . these observations are consistent with the charge distribution as shown for structures of compound 2 ( a ) and 2 ( b ) in scheme 1 . the c3 - n distance ( 1 . 300 ( 6 ) å ) is close to that observed in compound 1 ( 1 . 294 ( 3 ) å ). the n — ni bond length ( 1 . 900 ( 4 ) å ) is 0 . 055 å is shorter than that of compound 1 ( 1 . 9555 ( 18 ) å ), revealing a more electron deficient metal center in the zwitterionic compound . the zwitterionic initiators / catalysts enable the polymerization of olefins . in particular , the olefin , preferably a monomer , is selected from the group consisting essentially of : ( 1 ) olefins having formula r v ch ═ ch 2 , wherein r v is hydrogen , a substituted or unsubstituted hydrocarbyl group , or a substituted or unsubstituted hydrocarbyl bearing functional group ; ( 2 ) a substituted or unsubstituted cyclopentene , ( 3 ) a substituted or unsubstituted styrene , ( 4 ) a substituted or unsubstituted norbornene derivative bearing functional group , and ( 5 ) a polar olefin . preferred olefins are polypropylene and ethylene for the formation of polypropylene and high density polyethylene . the zwitterionic catalysts of this invention catalyze the formation of polypropylene and high molecular weight polyethylene , e . g ., having a molecular weight from 50 k to over a million daltons ethylene polymerization reactions with compound for 2 were studied , and the results of these studies are listed in table 1 . addition of 100 psi ethylene to a solution of compound 2 in toluene at 30 ° c . results in the quick consumption of the monomer and polymer formation ( example 1 ). use of an additional 6 equivalents of b ( c 6 f 5 ) 3 increases the activity of the catalyst and decreases the polydispersity index ( pdi ) of the polymer ( example 2 ). the pdi is a measure of the distribution of molecular weights in a given polymer sample and is the weight average molecular weight divided by the number average molecular weight . it indicates the distribution of individual molecular weight number average molecular weights in a batch of polymers . the pdi has a value always greater than 1 , but as the polymer chains approach uniform chain length , the pdi approaches unity . thermal analysis indicates the polymer has high melting point , consistent with the highly linear polymer structure ( 7 branches / 1000 carbons ) revealed by 1 h nmr spectroscopy . the activity increases with temperature and at 75 ° c . ( entries 3 and 4 ) it is comparable to those of cationic diimine nickel initiators [ 3 ]. the polymers formed at high temperature have broad pdi , more branching in the backbone ( 23 branches / 1000 carbons ) and lower melting points . no reaction occurs by using compound 1 ( example 5 ). compound 2 also initiates propylene polymerization to produce high molecular weight pp ( table 1 , entries 6 - 8 ). the product is purified by precipitation from toluene using acetone . 13 c nmr spectroscopy indicates the pp is isotactic rich with an mmmm pentad fraction of 0 . 6 . in contrast , diimine nickel initiators provide atactic or syndiotactic structures [ 3 , 26 ]. chain - end control by using compound 2 is suggested by the observation of mmrm sequence and absence of mmrr and mrrm sequences [ 27 ]. signals at 36 . 7 , and 30 . 2 ppm in the 13 c nmr spectra reveal the presence of polyethylene segments , which were observed previously in the pp formed with cationic ni ( diimine ) initiators . it has been previously proposed that 2 , 1 monomer insertion and subsequent chain walking to give 1 , ω - enchainments results in these linear segments [ 1 ]. the pp obtained has a broad tm at 70 ° c . and a tg at − 23 ° c . example 4 can be repeated with a catalyst of formula 1 in which m is pd , l ′ is phosphine , r ′ is methyl , x ′ is carbonyl , r is methyl , r ″ is ethyl , r ″′ is phenyl , r iv is hydrogen , n is 1 and l is oxygen , x ″ is amine , and la is al ( c 6 f 5 ) 3 . example 4 can be repeated with a catalyst of formula 1 in which m is pt , l ′ is amine , r ′ is ethyl , x ′ is imine , r is ethyl , r ″ is propyl , r ″′ is hydrogen , r iv is hydrogen , n is 0 , x ″ is phosphine , and la is a proton . example 4 can be repeated with a catalyst of formula 1 in which m is pd , l ′ is ether , r ′ is propyl , x ′ is phosphine , r is ethyl , r ″ is propyl , r ″′ is n - methyl phenyl , r iv is methyl , n is 1 and l is amine , x ″ is oxygen , and la is bf 3 . example 4 can be repeated using an olefin having formula r v ch ═ ch 2 , wherein r v is a hydrocarbyl group . example 4 can be repeated using an olefin having formula r v ch ═ ch 2 , wherein r v is styrene as the olefin . example 4 can be repeated using a norbornene bearing functional group as the olefin . in summary , we have demonstrated that a zwitterionic nickel complex supported by the 3 -( 2 , 6 - diisopropylphenylimino )- but - 1 - en - 2 - olato ligand can be used to prepare high molecular weight pe and pp . the most noteworthy feature of the active site is that it is supported by an olefinic fragment , which lacks substantial steric hindrance . such a structure departs from previous structure / reactivity relationships and theoretical predictions for cationic ni ( diimine ) complexes , which require sterically demanding substituents to produce high molecular weight pe . bonding from an olefin is considerably different from that of a nitrogen donor in that on - back bonding is a possibility . whether this electronic feature is responsible for the increasing the ratio of the rate of chain propagation , relative to chain transfer or termination rates is unknown at this stage and requires theoretical analysis for elucidation . although the present invention has been described in connection with the preferred embodiments , it is to be understood that modifications and variations may be utilized without departing from the principles and scope of the invention , as those skilled in the art will readily understand . accordingly , such modifications may be practiced within the scope of the following claims . 1 . ittel , s . d . ; 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