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Upstream product

• 96506-59-1 N,N′-bis(2-hydroxy-3,5-di-tert-butylphenyl)ethylenediamine 
• 1144018-46-1 N,N′-bis(2-hydroxy-3,5-di-tert-butylphenyl)-4,5-dihydroimidazolinium chloride 
• 31406-67-4 tetra(benzyl)hafnium 

Relevant academic research and scientific papers

Neutral and cationic N-heterocyclic carbene zirconium and hafnium benzyl complexes: Highly regioselective oligomerization of 1-hexene with a preference for trimer formation

Various zirconium and hafnium amido, chloro, and benzyl complexes supported by a tridentate N-heterocyclic carbene bis-phenolate dianionic ligand ((OCO)2-) have been synthesized and structurally characterized. The alcohol elimination reaction of the protio ligand N,N′-bis(2-hydroxy-3,5- di-tert-butylphenyl)-4,5-dihydroimidazolium chloride (1) and the metal alkoxide precursors M(OiPr)4(HOiPr) (M = Zr, Hf) and a subsequent alkoxide/chloride exchange reaction (upon addition of trimethylsilyl chloride, TMSCl) afforded the corresponding Zr and Hf carbene dichloro complexes as THF adducts: (OCO)MCl2(THF) (2a-THF, M = Zr; 2b-THF, M = Hf). As determined by single-crystal X-ray crystallographic studies, the molecular structure of the Hf derivative 2b-THF confirmed the proposed formulation and the effective formation of a (OCO)Hf chelate. In the case of Zr, an amine elimination reaction between protio ligand 1 and Zr(NMe2)4 yielded the corresponding Zr amido THF adduct (OCO)Zr(NMe2)(Cl)(THF) (3a-THF) when carried in THF as a solvent, while the Zr-NHMe2 adduct (OCO)Zr(NMe2)(NHMe2)(THF) (3a-NHMe2) was isolated using CH2Cl2 as the reaction solvent. 3a-THF may be readily and quantitatively converted to the dichloro derivative 2a-THF upon addition of TMSCl. The toluene elimination reaction of protio ligand 1 and M(CH2Ph)4 (M = Zr, Hf) followed by a salt metathesis with 1 equiv of PhCH2MgCl afforded the corresponding Zr and Hf carbene dibenzyl complexes (OCO)M(CH2Ph)2 (4a, M = Zr; 4b, M = Hf), whose solid-state structures were confirmed by X-ray crystallography. 4a and 4b each feature a five-coordinate metal center with both benzyl moieties binding in a η2 fashion. The protonolysis reaction between species 4a (or 4b) and [HNMe2Ph][B(C6F5) 4] afforded the clean and quantitative formation of the corresponding Zr (or Hf) anilinium benzyl cation 5a+ (or 5b+). Remarkably, the cation 5a+ catalyzes the highly regioselective oligomerization of 1-hexene with a marked preference for trimer formation.

Unusual Benzyl Migration Reactivity in NHC-Bearing Group 4 Metal Chelates: Synthesis, Characterization, and Mechanistic Investigations

The reaction of 1 equiv of [M(CH2Ph)4] (M = Zr, Hf) and 1,3-bis(3,5-di-tert-butyl-2-hydroxyphenyl)imidazolinium chloride [tBu(OCO)H3, 1] cleanly yielded the corresponding M-NHC chloro benzyl derivatives [[tBu(OCO)]M(Cl)(CH2Ph)] (2Zr and 2Hf) along with 3 equiv of toluene. For both metal complexes, the effective formation of a (κ3-OCO) metal chelate and the coordination of a benzyl ligand onto the M(IV) metal center were established by NMR and elemental analysis. In contrast, under identical conditions, the reaction of Ti(CH2Ph)4 with the imidazolinium proligand 1 yielded the unexpected rearranged dimer product 3Ti, arising from the migration of the Ti-Bn group from the metal center to the Ccarbene atom. The molecular structure of 3Ti was established by analogy with the X-ray-determined Zr analogue 3Zr. Compound 3Zr quantitatively formed upon heating a benzene solution of 2Zr at 60 °C. In the solid state, compound 3Zr consists of two seven-coordinate mononuclear Zr fragments that are associated by two bridging μ2-chloride atoms, confirming the migration of the Zr-Bn moiety from the metal center to the Ccarbene atom. Carrying out the reaction of [M(CH2Ph)4] (M = Ti, Zr, Hf) with imidazolinium proligand 1 in THF led to the quantitative formation of the corresponding rearranged monomeric THF adduct [[tBu(OC(Bn)O)]M(Cl)(THF)] (4Ti-THF, 4Zr-THF, and 4Hf-THF), as established by X-ray crystallographic studies in the case of 4Ti-THF. Such a THF-promoted benzyl migration was also observed with the dibenzyl Zr and Hf complexes [[tBu(OCO)]M(CH2Ph)2] (5Zr and 5Hf), leading to the formation of the corresponding THF-rearranged products [[tBu(OC(Bn)O)]M(CH2Ph)(THF)] (6Zr-THF and 6Hf-THF). The addition of 1 equiv of methylmagnesium bromide (CH3MgBr) or phenylmagnesium bromide (PhMgBr) to 1 equiv of the zirconium dichloro NHC complex [[tBu(OCO)]Zr(Cl)2(THF)] (8) in THF yielded the rearranged products [[tBu(OC(Me)O)]M(Cl)(THF)] (9Me) and [[tBu(OC(Ph)O)]M(Cl)(THF)] (9Ph), respectively, as deduced from NMR data. Kinetic studies were carried out on the THF-promoted rearrangement reaction of the benzyl chloro Hf derivative 2Hf in the presence of THF to produce 4Hf-THF. These data are consistent with the reaction rate law being first order both in THF and in the THF adduct 2Hf-THF. DFT calculations on the Ti, Zr, and Hf systems support a benzyl migration reaction occurring at a transient heptacoordinated bis-THF adduct species of the type [[tBu(OCO)]M(Cl)(Bn)(THF)2], which may readily form upon THF coordination to 2Hf-THF.

N-HETEROCYCLIC CARBENE BASED ZIRCONIUM COMPLEXES FOR USE IN LACTONES RING OPENING POLYMERIZATION

This invention is reporting new N-heterocyclic carbene based zirconium (or hafnium) complexes and their uses as catalysts for the lactones ring opening polymerization. These new catalysts are robust and versatile and exert control over polymer molecular weight and/or stereochemistry and exhibit high reactivity (cf. for low temperature applications). In particular the new catalysts show both enhanced activity and at the same time a better selectivity than the catalysts employed by the prior art.