Synthesis, Structure, and Reactivity of Organometallic .pi.-Complexes of the Rare Earths in the Oxidation State Ln3+ with Aromatic Ligands

Schumann, Herbert; Meese-Marktscheffel, Juliane A.; Esser, Lothar

doi:10.1021/cr00036a004

Cited by 755 publications

(532 citation statements)

References 55 publications

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“…This has been attributed to the more electron donating ability of the BH 4 than that of the chloride [10]. In contrast, halide analogues often display an anionic, "ate" molecular structure [34], as exemplified by the wellknown Cp* 2 NdCl 2 Li(OEt 2 ) 2 [35]. A few examples of anionic bisborohydride metallocene-like complexes were described for the early series but they bear poor electron donating ligands [24,25].…”

Section: ((Equation 2))mentioning

confidence: 99%

Synthesis and X-ray structure of a borohydrido metallocene of neodymium and its use as pre-catalyst in Nd/Mg dual-component ethylene and isoprene polymerisations

Visseaux

Chenal

Roussel

et al. 2006

Journal of Organometallic Chemistry

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Cp* 2 Nd(BH 4 )(THF) (1) (Cp* = C 5 Me 5 ) has been readily obtained in one step from Nd(BH 4 ) 3 (THF) 3 and fully characterized by 1 H NMR, IR spectroscopy, and elemental analysis. Its X-Ray structure displays a neutral monomeric complex, bearing one slightly distorted terminal BH 4group. Associated to nBuEtMg, 1 affords a highly active catalyst for ethylene polymerisation, the first one prepared from a borohydrido organolanthanide pre-catalyst. In the same experimental conditions, the catalytic behaviour of 1 is similar to that of previously described Cp* 2 NdCl 2 Li(Et 2 O) 2 (2). The 1/nBuEtMg system is not deactivated even in the presence of large excesses of THF. In contrast to its chloro homologue 2, the addition of 1 equivalent of nBuEtMg to 1 affords a catalyst for a trans-selective polymerisation of isoprene.2

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Section: ((Equation 2))mentioning

confidence: 99%

Synthesis and X-ray structure of a borohydrido metallocene of neodymium and its use as pre-catalyst in Nd/Mg dual-component ethylene and isoprene polymerisations

Visseaux

Chenal

Roussel

et al. 2006

Journal of Organometallic Chemistry

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“…At the same time a number of direct' contacts with X = H (370 of 1824) were observed, which can conform to agostic interactions LnÁ Á ÁHÐC. Such interactions are due to the unsaturated valent capabilities of Ln atoms (Schumann et al, 1995) which have often been described in the literature. Ordinarily, an agostic interaction is determined by the geometrical analysis of crystal structure through the presence of suf®ciently short LnÁ Á ÁH distances taking into account the lengthening RÐC bonds in the groups RÐCÐHÁ Á ÁLn.…”

Section: Agostic Contactsmentioning

confidence: 98%

“…Hereafter, the CN of a Ln atom is considered as the total number of atoms of a ligand (L) taking part in valent interactions LnÐL, unlike ef®cient CN (Schumann et al, 1995). The authors (Xi-Geng et al, 1997;Hitchcock et al, 1992) have described the complex NIJFOB as a tetramer and the complex YAMNIJ as a polymeric chain, and in both structures the Ln atoms are connected with bridging cyclopentadienyl rings.…”

Section: Computer Identification Of Atomic Bondsmentioning

confidence: 99%

Study of rare-earth π-complexes by means of Voronoi–Dirichlet polyhedra

Blatova

Блатов

Сережкин

2001

Acta Crystallogr Sect B

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An investigation of 135 %-complexes of rare-earth atoms (Ln) was carried out with Voronoi±Dirichlet polyhedra. A novel method for the evaluation of the sizes of polyatomic ligands and steric effects in the structure of organometallic compounds was developed. The dependence of the domain size for Ln atoms on their nature, coordinating number and oxidation state was studied. The reasons for the occurrence of agostic LnÐH contacts were considered with a geometrical± topological analysis.

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“…This complex produced very linear PE with higher melting points in the range of 134-139°C which indicate high-density polyethylene (HDPE). Hf-catalyst 67 was less active (40 kg mol cat -1 h -1 bar -1 ) for the ethylene polymerization but produced very high molecular weight polyethylene (UHMWPE) with M n = 4,700,000 g mol -1 and molecular weight distribution = 1.3 [75][76][77][78][79][80][81]. Presumably, the greater ionic radius and less electrophilicity of electron-deficient Hf-centre in 67 is helpful for getting very high molecular weight polymer.…”

Section: Group-4 Silylamido Complexesmentioning

confidence: 99%

Aminopyridine stabilized group-IV metal complexes and their applications

Hafeez

Muhammad

2016

Appl Petrochem Res

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During the last two decades, group-IV metalsbased aminopyridinato complexes have attracted a tremendous research interest because of immense industrial needs for the catalyst which would be of higher activity and selectivity with lower toxicity and lower cost. Chemistry of titanium (Ti) and zirconium (Zr) complexes was more extensively explored as compared to hafnium (Hf) complexes. Direct synthesis, salt metathesis, amine elimination, alkane elimination, silyl chloride elimination, hydrogen chloride elimination and toluene elimination protocols have been used for the synthesis of group-IV metal complexes. Changes in ligand and complex design were made to optimize these catalysts for olefin polymerization. Most of these complexes have shown good catalytic activities when activated with dry methyl aluminoxane. Ligand transfer to aluminum was found in these complexes, particularly with less bulky ligands, and this ligand transfer problem was overcome by tridentate ligands but the activities of these complexes were not competitive to complexes with bidentate aminopyridinato ligands. Majority of these complexes produce high-molecularweight polymers with broader molecular weight distributions, and Hf-complexes produce longer chain polymers than their comparative Ti and Zr aminopyridinato complexes. It could be deduced that group-IV metals inherit the potential for optimal polymerizing catalysts probably, because of their almost vacant d-orbitals, these act as hard acids which on combination with soft bases carry the opportunity to design and develop polymerization catalysts which could overcome the problems associated with existing systems.

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Synthesis, Structure, and Reactivity of Organometallic .pi.-Complexes of the Rare Earths in the Oxidation State Ln3+ with Aromatic Ligands

Cited by 755 publications

References 55 publications

Synthesis and X-ray structure of a borohydrido metallocene of neodymium and its use as pre-catalyst in Nd/Mg dual-component ethylene and isoprene polymerisations

Synthesis and X-ray structure of a borohydrido metallocene of neodymium and its use as pre-catalyst in Nd/Mg dual-component ethylene and isoprene polymerisations

Study of rare-earth π-complexes by means of Voronoi–Dirichlet polyhedra

Aminopyridine stabilized group-IV metal complexes and their applications

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