Olefin polymerization catalyst precursors

Ward, D.G. (W.R. Grace and Co.-Conn., USA) (1996) Supported olefin polymerization catalyst precursors, their preparation and use. PCT Int. Appl. 96/13531. 

A.J. Rossini, I. Hung, S.A. Johnson, C. Slebodnick, M. Mensch, P.A. Deck, R.W. Schurko, Solid-state Zr NMR spectroscopy studies of zirconocene olefin polymerization catalyst precursors, J. Am. Chem. Soc. 132 (2010) 18301—18317. 

Treatment of [(CsMe4SiMe2N-t-Bu)Sc(PMe3)(/i-H)]2 with two equivalents of propylene at low temperature yielded the structurally characterized phosphine-free di-p-propyl complex [(C5Me4SiMe2N-t-Bu)Sc(/i-nPr)]2. This dimeric organoscandium alkyl was found to be an even more active a-olefin polymerization catalyst than the hydride precursor [52],... 

Thus eleven N-amino-N-heterocycles were synfhesized. Together with the commercially available unsubstituted N-amino-pyrrole, twelve different N-amino-azoles became available as ligand precursor. Their properties - with regard of their intended use as steering groups in the ligand backbone of the olefin polymerization catalysts - differ in terms of steric bulk of the substituents, symmetry, and electronic properties, as can be seen from inspecting Chart 3.1. 

BF4-. CIO4-) salts.240 Furthermore, (CGC)Ti(III) catalyst precursors can be activated with ferrocenium tetrakis(pentafluorophenyl)borate and oxidized to cationic Ti(IV) species 75. which is a very active olefin polymerization catalyst (eq 46). Another disclosure... 

S. Nagy, B.P, Etherton, R. Krishnamurti, and J. Tyrell, U.S. Pat. No. 6,232,260 (2001). These researchers reacted p-tolylhydrazine with 1-indanone to form a precursor, which was converted in subsequent reactions to an olefin polymerization catalyst. Draw the product from the first reaction. 

The most famous mechanism, namely Cossets mechanism, in which the alkene inserts itself directly into the metal-carbon bond (Eq. 5), has been proposed, based on the kinetic study [134-136], This mechanism involves the intermediacy of ethylene coordinated to a metal-alkyl center and the following insertion of ethylene into the metal-carbon bond via a four-centered transition state. The olefin coordination to such a catalytically active metal center in this intermediate must be weak so that the olefin can readily insert itself into the M-C bond without forming any meta-stable intermediate. Similar alkyl-olefin complexes such as Cp2NbR( /2-ethylene) have been easily isolated and found not to be the active catalyst precursor of polymerization [31-33, 137]. In support of this, theoretical calculations recently showed the presence of a weakly ethylene-coordinated intermediate (vide infra) [12,13]. The stereochemistry of ethylene insertion was definitely shown to be cis by the evidence that the polymerization of cis- and trans-dideutero-ethylene afforded stereoselectively deuterated polyethylenes [138]. 

When a chiral ansa-type zirconocene/MAO system was used as the catalyst precursor for polymerization of 1,5-hexadiene, an main-chain optically active polymer (68% trans rings) was obtained84-86. The enantioselectivity for this cyclopolymerization can be explained by the fact that the same prochiral face of the olefins was selected by the chiral zirconium center (Eq. 12) [209-211]. Asymmetric hydrogenation, as well as C-C bond formation catalyzed by chiral ansa-metallocene 144, has recently been developed to achieve high enantioselectivity88-90. This parallels to the high stereoselectivity in the polymerization. 

The patent literature contains several references to the use of sulfoxide complexes, usually generated in situ, as catalyst precursors in oligomerization and polymerization reactions. Thus, a system based upon bis(acrylonitrile)nickel(0> with added Me2SO or EtgSO is an effective cyclotrimerization catalyst for the conversion of butadiene to cyclo-1,5,-9-dodecatriene (44). A similar system based on titanium has also been reported (407). Nickel(II) sulfoxide complexes, again generated in situ, have been patented as catalyst precursors for the dimerization of pro-pene (151) and the higher olefins (152) in the presence of added alkyl aluminum compounds. 

An example is provided by the structures of Group IV metallacycles, LL MCl2, where ligands L and L are cyclopentadienyl based and M is Ti or Zr. As a class, these compounds act as catalyst precursors in homogenous (Ziegler-Natta) polymerization of olefins, e.g. 

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