Silica-Supported Pentamethylcyclopentadienyl Ytterbium(II) and Samarium(II) Sites: Ultrahigh Molecular Weight Polyethylene without Co-Catalyst.

Title Silica-Supported Pentamethylcyclopentadienyl Ytterbium(II) and Samarium(II) Sites: Ultrahigh Molecular Weight Polyethylene without Co-Catalyst.
Authors F. Allouche; K.Wing Chan; A. Fedorov; R.A. Andersen; C. Copéret
Journal Angew Chem Int Ed Engl
DOI 10.1002/anie.201800542
Abstract

Designing highly active supported ethylene polymerization catalysts that do not require a co-catalyst to generate electrophilic metal alkyl species is still a challenge despite its industrial relevance. Described herein is the synthesis and characterization of well-defined silica-supported cyclopentadienyl Ln sites (Ln=Yb and Sm) of general formula [(?SiO)LnCp*]. These well-defined surface species are highly activite towards ethylene polymerization in the absence of added co-catalyst. Initiation is proposed to occur by single electron transfer.

Citation F. Allouche; K.Wing Chan; A. Fedorov; R.A. Andersen; C. Copéret.Silica-Supported Pentamethylcyclopentadienyl Ytterbium(II) and Samarium(II) Sites: Ultrahigh Molecular Weight Polyethylene without Co-Catalyst.. Angew Chem Int Ed Engl. 2018;57(13):34313434. doi:10.1002/anie.201800542

Related Elements

Samarium

See more Samarium products. Samarium (atomic symbol: Sm, atomic number: 62) is a Block F, Group 3, Period 6 element with an atomic radius of 150.36. Samarium Bohr ModelThe number of electrons in each of samarium's shells is 2, 8, 18, 24, 8, 2 and its electron configuration is [Xe]4f6 6s2. The samarium atom has a radius of 180 pm and a Van der Waals radius of 229 pm. In its elemental form, samarium has a silvery-white appearance. Elemental Samarium PictureSamarium is not found as free element in nature. It is found in the minerals cerite, gadolinite, samarskite, monazite and bastnäsite. Samarium is classified as a rare earth element and is the 40th most abundant element in the Earth's crust. Samarium was discovered and first isolated by Lecoq de Boisbaudran in 1879. It is named after the mineral samarskite, the mineral from which it was isolated.

Ytterbium

See more Ytterbium products. Ytterbium (atomic symbol: Yb, atomic number: 70) is a Block F, Group 3, Period 6 element with an atomic weight of 173.054. Ytterbium Bohr ModelThe number of electrons in each of Ytterbium's shells is [2, 8, 18, 32, 8, 2] and its electron configuration is [Xe]4f14 6s2. The Ytterbium atom has a radius of 176 pm and a Van der Waals radius of 242 pm. Ytterbium was discovered by Jean Charles Galissard de Marignac in 1878 and first isolated by Georges Urbain in 1907.Elemental Ytterbium In its elemental form, ytterbium has a silvery-white color. Ytterbium is found in monazite sand as well as the ores euxenite and xenotime. Ytterbium is named after Ytterby, a village in Sweden. Ytterbium can be used as a source for gamma rays, for the doping of stainless steel, or other active metals. Its electrical resistivity rises under stress, making it very useful for stress gauges that measure the deformation of the ground in the even of an earthquake.

Silicon

See more Silicon products. Silicon (atomic symbol: Si, atomic number: 14) is a Block P, Group 14, Period 3 element with an atomic weight of 28.085. Silicon Bohr MoleculeThe number of electrons in each of Silicon's shells is 2, 8, 4 and its electron configuration is [Ne] 3s2 3p2. The silicon atom has a radius of 111 pm and a Van der Waals radius of 210 pm. Silicon was discovered and first isolated by Jöns Jacob Berzelius in 1823. Silicon makes up 25.7% of the earth's crust, by weight, and is the second most abundant element, exceeded only by oxygen. The metalloid is rarely found in pure crystal form and is usually produced from the iron-silicon alloy ferrosilicon. Elemental SiliconSilica (or silicon dioxide), as sand, is a principal ingredient of glass, one of the most inexpensive of materials with excellent mechanical, optical, thermal, and electrical properties. Ultra high purity silicon can be doped with boron, gallium, phosphorus, or arsenic to produce silicon for use in transistors, solar cells, rectifiers, and other solid-state devices which are used extensively in the electronics industry.The name Silicon originates from the Latin word silex which means flint or hard stone.

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