Jerzy Klosin

Development of Group IV Molecular Catalysts for High Temperature Ethylene-α-Olefin Copolymerization Reactions

This Account describes our research related to the development of molecular catalysts for solution phase olefin polymerization. Specifically, a series of constrained geometry and nonmetallocene (imino-amido-type) complexes were developed for high temperature olefin polymerization reactions. We have discovered many highly active catalysts that are capable of operating at temperatures above 120 °C and producing copolymers with a useful range of molecular weights (from medium to ultrahigh depending on precatalyst identity and polymerization conditions) and α-olefin incorporation capability. Constrained geometry catalysts (CGCs) exhibit very high activities and are capable of producing a variety of copolymers including ethylene-propylene and ethylene-1-octene copolymers at high reactor temperatures. Importantly, CGCs have much higher reactivity toward α-olefins than classical Ziegler-Natta catalysts, thus allowing for the production of copolymers with any desired level of comonomer. In search of catalysts with improved performance, we discovered 3-amino-substituted indenyl-based CGCs that exhibit the highest activity and produce copolymers with the highest molecular weight within this family of catalysts. Phenanthrenyl-based CGCs were found to be outstanding catalysts for the effective production of high styrene content ethylene-styrene copolymers under industrially relevant conditions. In contrast to CGC ligands, imino-amido-type ligands are bidentate and monoionic, leading to the use of trialkyl group IV precatalysts. The thermal instability of imino-amido complexes was addressed by the development of imino-enamido and amidoquinoline complexes, which are not only thermally very robust, but also produce copolymers with higher molecular weights, and exhibit improved α-olefin incorporation. Imido-amido and imino-enamido catalysts undergo facile chain transfer reactions with metal alkyls, as evidenced by a sharp decrease in polymer molecular weight when the polymerization reactions were conducted in the presence of diethylzinc, an essential requirement for use in the production of olefin block copolymers via chain shuttling polymerization. Overall, the excellent characteristics of imino-amido-type catalysts, including high catalytic activities and ultrahigh molecular weight capabilities, make them good candidates for high temperature syntheses of block and random ethylene-α-olefin copolymers. Additionally, trialkyl imino-enamido complexes react quickly with various protic and unsaturated organic fragments, leading to a library of dialkyl precatalysts that, in several instances, resulted in superior catalysts. In conjunction with the development of transition metal catalysts, we also synthesized and evaluated activators for olefin polymerization. We found, for example, that, when conducted in coordinating solvents, the reaction between aluminum alkyls and tris(pentafluorophenyl)borane leads to the exclusive formation of alumenium borates, which are excellent activators for CGC complexes. Additionally, we developed a series of highly effective new activators featuring a very weakly coordinating anion composed of two Lewis acids coordinated to an imidazole fragment.

Facing Unexpected Reactivity Paths with ZrIV–Pyridylamido Polymerization Catalysts

This work provides original insights to the better understanding of the complex structure-activity relationship of Zr(IV)-pyridylamido-based olefin polymerization catalysts and highlights the importance of the metal-precursor choice (Zr(NMe(2))(4) vs. Zr(Bn)(4)) to prepare precatalysts of unambiguous identity. A temperature-controlled and reversible σ-bond metathesis/protonolysis reaction is found to take place on the Zr(IV)-amido complexes in the 298-383 K temperature range, changing the metal coordination sphere dramatically (from a five-coordinated tris-amido species stabilized by bidentate monoanionic {N,N(-)} ligands to a six-coordinated bis-amido-mono-amino complexes featured by tridentate dianionic {N(-),N,C(-)} ligands). Well-defined neutral Zr(IV)-pyridylamido complexes have been prepared from Zr(Bn)(4) as metal source. Their cationic derivatives [Zr(IV) N(-),N,C(-)}Bn](+)[B(C(6)F(5))(4)](-) have been successfully applied to the room-temperature polymerization of 1-hexene with productivities up to one order of magnitude higher than those reported for the related Hf(IV) state-of-the-art systems. Most importantly, a linear increase of the poly(1-hexene) M(n) values (30-250 kg mol(-1)) has been observed upon catalyst aging. According to that, the major active species (responsible for the increased M(n) polymer values) in the aged catalyst solution, has been identified.

13C NMR of polyolefins with a new high temperature 10 mm cryoprobe

Recently, a high temperature 10 mm cryoprobe was developed. This probe provides a significant sensitivity enhancement for (13)C NMR of polyolefins at a sample temperature of 120-135 degrees C, as compared to conventional probes. This greatly increases the speed of NMR studies of comonomer content, sequence distribution, stereo- and regioerrors, saturated chain end, unsaturation, and diffusion of polymers. In this contribution, we first compare the (13)C NMR sensitivity of this probe with conventional probes. Then, we demonstrate one of the advantages of this probe in its ability to perform 2D Incredible Natural Abundance Double Quantum Transfer Experiment (2D INADEQUATE) in a relatively short period of time. The 2D INADEQUATE has been rarely used for polymer studies because of its inherently very low sensitivity. It becomes even more challenging for studying infrequent polyolefin microstructures, as low probability microstructures represent a small fraction of carbons in the sample. Here, the 2D INADEQUATE experiment was used to assign the (13)C NMR peaks of 2,1-insertion regioerrors in a poly(propylene-co-1-octene) copolymer.

Synthesis of new compounds related to the commercial fungicide tricyclazole.

BACKGROUND Tricyclazole is a commercial fungicide used to control rice blast. As part of re-registration activities, samples of metabolites and process impurities are required. In addition, isotopically labeled tricyclazole samples are also required. RESULTS Four new compounds related to tricyclazole are reported. An isotopically labeled sample of tricyclazole was prepared that contained two (15)N atoms and one (13)C atom. Radiolabeled tricyclazole with (14)C at the triazole C3 position was also synthesized. A new process impurity in technical tricyclazole was identified and synthesized. A new metabolite of tricyclazole was identified, independently synthesized and characterized by X-ray crystallography. CONCLUSION A previously unreported metabolite of tricyclazole has been identified and structurally characterized. In addition, a new process impurity has been identified by independent synthesis. Identification of these new compounds has facilitated the continued registration of this important fungicide.

X-ray and computational studies of some 5-(perfluoroalkenyl) uracils

Abstract X-ray structures of 1,3-dimethyl-5-trifluorovinyl-, 5- E - and Z -pentafluoroalkenyl uracils (compounds 1 , 2 , 3 ) were determined. In all cases planar ring of uracil was slightly distorted around C2, C4, N3 and C6 atoms. The exocyclic alkenyl group is not coplanar with uracil ring and exocyclic CC bond was shortened when compared with typical alkenes. Using semiempirical (MNDO, AM1, PM3) and ab initio (RHF 4-31 G) methods the structures of stable conformers were determined and obtained geometries were compared with those found experimentally.

Two Forms of Bromo(cycloheptatrienylidene)bis(triphenylphosphine)platinum(II)

The title complex crystallizes in two different crystal systems : one form in the monoclinic system, as [PtBr(C 7 H 6 )(C 18 H 15 P) 2 ]BF 4 .CD 2 Cl 2 .C 4 D 8 O, and the other in the orthorhombic crystal system, as [PtBr-(C 7 H 6 )(C 18 H 15 P) 2 ]BF 4 .C 4 H 8 O. The crystal structure determination of the complex bromo(cycloheptatrienylidene)bis(triphenylphosphine)platinum(II), [PtBr(C 7 H 6 )(C 18 H 15 P) 2 ], revealed that the Pt II cation is coordinated to a Br atom, two triphenylphosphine donors and cycloheptatrienylidene. The complex has square-planar geometry around Pt with the triphenylphosphine ligands being trans to each another. The plane of the cycloheptatrienylidene ligand is almost perpendicular to the coordination plane.

Synthesis and molecular structure of two zirconocene complexes of cyclooctatrienyne

Abstract Two zirconocene complexes of cyclooctatrienyne have been prepared by β-hydrogen elimination from zirconocene biscyclooctatetraenyl. Both complexes are fluxional by a ring inversion process with activation barriers in the range typical of cyclooctatetraenes. An X-ray crystal structure of 3a reveals a boat conformation of cyclooctatrienyne ring with no significant flattening when compared with cyclooctatetraene.

CCDC 857362: Experimental Crystal Structure Determination

Related Article: K.A.Frazier, R.D.Froese, Yiyong He, J.Klosin, C.N.Theriault, P.C.Vosejpka, Zhe Zhou, K.A.Abboud|2011|Organometallics|30|3318|doi:10.1021/om200167h