For the first time, new catalysts for olefin polymerization have been discovered through the application of fully integrated high-throughput primary and secondary screening techniques supported by rapid polymer characterization methods. Microscale 1-octene primary screening polymerization experiments combining arrays of ligands with reactive metal complexes M(CH(2)Ph)(4) (M = Zr, Hf) and multiple activation conditions represent a new high-throughput technique for discovering novel group (IV) polymerization catalysts. The primary screening methods described here have been validated using a commercially relevant polyolefin catalyst, and implemented rapidly to discover the new amide-ether based hafnium catalyst [eta(2)-(N,O)[bond](2-MeO[bond]C(6)H(4))(2,4,6-Me(3)C(6)H(2))N]Hf(CH(2)Ph)(3) (1), which is capable of polymerizing 1-octene to high conversion. The molecular structure of 1 has been determined by X-ray diffraction. Larger scale secondary screening experiments performed on a focused 96-member amine-ether library demonstrated the versatile high temperature ethylene-1-octene copolymerization capabilities of this catalyst class, and led to significant performance improvements over the initial primary screening discovery. Conventional one gallon batch reactor copolymerizations performed using selected amide-ether hafnium compounds confirmed the performance features of this new catalyst class, serving to fully validate the experimental results from the high-throughput approaches described herein.

The influence of tertiary phosphines on the stability of FeS3P coordination units and the formation of iron−sulfur clusters has been investigated. Reaction of [Fe4S4Cl4]2- with a small excess of PR3 in acetonitrile/THF affords the cubane-type clusters [Fe4S4(PR3)4]1+ (R = Cy, But, Pri), one-electron reduced over the initial cluster and possessing an S = 1/2 ground state. These clusters may be electrochemically oxidized to [Fe4S4(PR3)4]2+ and reduced to [Fe4S4(PR3)4], which can also be generated in solution by chemical reduction. The neutral clusters upon standing in solution lose phosphine and aggregate to form dicubane ([Fe8S8(PCy3)6]) or tetracubane ([Fe16S16(PR3)8]; R = But, Pri) clusters. The [Fe8S8]0 dicubane core has two intercubane Fe−S bonds, defining an Fe2S2 rhomb and affording a structure of overall idealized C 2h symmetry. The tetracubane clusters consist of a cyclic array of four cubanes joined in four Fe2S2 rhombs in a structure of overall D 4 symmetry, and present a new structural motif in Fe−S cluster chemistry. Tertiary phosphines impose two significant features on this cluster chemistry. These ligands significantly stabilize the [Fe4S4]1+/0 core oxidation levels compared to the case of conventional [Fe4S4L4]3-,4- clusters (L = monoanion). Ligands with cone angles exceeding that of PEt3 (132°) favor tetrahedral FeS3P coordination sites. This has the effect of directing reactions away from the formation of Fe6S6 (four trigonal pyramidal) and Fe6S8 (six square pyramidal) clusters having the indicated sites which are disfavored by large cone angles. Structural principles governing polycubane clusters together with a brief enumeration of stereochemically feasible polycubanes are presented and discussed.

The discovery of new olefin polymerization catalysts is currently a time-intensive trial-and-error process with no guarantee of success. A fully integrated high-throughput screening workflow for the discovery of new catalysts for polyolefin production has been implemented at Symyx Technologies. The workflow includes the design of the metal-ligand libraries using custom-made computer software, automated delivery of metal precursors and ligands into the reactors using a liquid-handling robot, and a rapid primary screen that serves to assess the potential of each metalligand-activator combination as an olefin polymerization catalyst. "Hits" from the primary screen are subjected to secondary screens using a 48-cell parallel polymerization reactor. Individual polymerization reactions are monitored in real time under conditions that provide meaningful information about the performance capabilities of each catalyst. Rapid polymer characterization techniques support the primary and secondary screens. We have discovered many new and interesting catalyst classes using this technology.

Ein Lehrbuchbeispiel für die Entdeckung, Optimierung und kommerzielle Nutzung eines Katalysators bietet die Entdeckung einer Klasse Hf‐basierter Nichtmetallocen‐Olefinpolymerisationskatalysatoren (siehe Bild; Hf orangefarbene Kugel, N blau, C(Me) grün), ihr aufwändiges Hochdurchsatz‐Screening und ihr industrieller Einsatz in einem Hochtemperaturlösungsprozess zur Herstellung von Materialien auf der Grundlage von hoch isotaktischem Polypropylen.

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