Highlights der Renaissance der Amidometallchemie
About: This article is published in Angewandte Chemie.The article was published on 2000-02-04. It has received 66 citations till now.
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TL;DR: In this paper, the coordination chemistry of electron-rich metal complexes with the simple aliphatic, anionic diphosphanylamido ligand {N(CH2CH2PR2)2} is covered and compared with other commonly used anionic PEP (E = C, N) pincer ligands.
Abstract: In this review, the coordination chemistry of electron-rich metal complexes with the simple aliphatic, anionic diphosphanylamido ligand {N(CH2CH2PR2)2}– is covered and compared with other commonly used, anionic PEP (E = C, N) pincer ligands. The strong π-basicity of this ligand enables both the stabilization of electronically and coordinatively highly unsaturated complexes and their use as cooperating ligands in bifunctional stoichiometric bond activation reactions and catalysis. Versatile ligand backbone dehydrogenation gives access to related enamido and dienamido ligands {(R2PCHCH)N(CH2CH2PR2)}– and {N(CHCHPR2)2}–, respectively. This oxidative functionalization enables fine-tuning of the ligand donor properties and thereby of the structural features, electronic structure, and reactivity of the respective complexes, which is discussed for several examples.
228 citations
TL;DR: In this article, the divalent bis(phosphinimino)methanide lanthanide complexes of composition [{(Me3SiNPPh2)2CH}Ln{(Ph2P)2N}(THF)] have been prepared by a salt metathesis reactions of K{CH(PPh2NSiMe3)2} and LnI2.
95 citations
TL;DR: The new family of Lewis base free hydrido complexes of rare-earth metals supported by guanidinate ligands was synthesized and structurally characterized and revealed that these complexes are dimeric in both solid state and in [D6]benzene.
Abstract: The new family of Lewis base free hydrido complexes of rare-earth metals supported by guanidinate ligands [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] (Ln = Y, Nd, Sm, Gd, Yb) was synthesized and structurally characterized. Single-crystal X-ray and solution NMR studies revealed that these complexes are dimeric in both solid state and in [D6]benzene. The dimeric hydrido complexes can adopt eclipsed (Nd, Sm, Gd) or staggered (Y, Yb, Lu) conformations depending on the metal-atom size. Catalytic activity of these [{Ln{(Me3Si)2NC(NiPr)2}2(mu-H)}2] complexes in the polymerization of ethylene, propylene, and styrene has been investigated. Complexes of Sm and Y have high catalytic activity in ethylene polymerization (1268 and 442 g mmol(-1) atm(-1) h(-1), respectively).
94 citations
TL;DR: A review of main group and transition metal complexes of N,N-disubstituted and mono-bridged bis(aminotroponiminate)s can be found in this article.
Abstract: This article reviews recent progress of main group and
transition metal complexes of N,N'-disubstituted
aminotroponiminates and mono-bridged bis(aminotroponiminate)s. Recent
developments have shown that aminotroponiminates can stabilise low valent
main group metals and that they can be used in early transition metal
chemistry as cyclopentadienyl alternatives. The structural properties and
the reactivity of these complexes as well as the catalytic and synthetic
applications of aminotroponiminate complexes will be outlined in this
article.
92 citations
TL;DR: This tutorial review describes the main results obtained over the past decade in order to introduce the reader to an exciting field which currently shows particularly rapid development in coordination chemistry.
Abstract: Dppf is one of the most useful and popular ligands in coordination chemistry. Its overwhelming success has overshadowed and arguably even delayed the development and use of closely related ferrocene-based ligands with two ligating N, O or S atoms. Recently, however, dynamic progress concerning such homo-donor ligands can be noted. This tutorial review describes the main results obtained over the past decade in order to introduce the reader to an exciting field which currently shows particularly rapid development. The material is organised in sections according to ligand type, followed by a section which summarises the applications reported so far.
84 citations
References
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TL;DR: In this paper, the synthesis of mesoporous inorganic solids from calcination of aluminosilicate gels in the presence of surfactants is described, in which the silicate material forms inorganic walls between ordered surfactant micelles.
Abstract: MICROPOROUS and mesoporous inorganic solids (with pore diameters of ≤20 A and ∼20–500 A respectively)1 have found great utility as catalysts and sorption media because of their large internal surface area. Typical microporous materials are the crystalline framework solids, such as zeolites2, but the largest pore dimensions found so far are ∼10–12 A for some metallophosphates3–5 and ∼14 A for the mineral cacoxenite6. Examples of mesoporous solids include silicas7 and modified layered materials8–11, but these are invariably amorphous or paracrystalline, with pores that are irregularly spaced and broadly distributed in size8,12. Pore size can be controlled by intercalation of layered silicates with a surfactant species9,13, but the final product retains, in part, the layered nature of the precursor material. Here we report the synthesis of mesoporous solids from the calcination of aluminosilicate gels in the presence of surfactants. The material14,15 possesses regular arrays of uniform channels, the dimensions of which can be tailored (in the range 16 A to 100 A or more) through the choice of surfactant, auxiliary chemicals and reaction conditions. We propose that the formation of these materials takes place by means of a liquid-crystal 'templating' mechanism, in which the silicate material forms inorganic walls between ordered surfactant micelles.
15,125 citations
TL;DR: In this paper, the synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described.
Abstract: The synthesis, characterization, and proposed mechanism of formation of a new family of silicatelaluminosilicate mesoporous molecular sieves designated as M41S is described. MCM-41, one member of this family, exhibits a hexagonal arrangement of uniform mesopores whose dimensions may be engineered in the range of - 15 A to greater than 100 A. Other members of this family, including a material exhibiting cubic symmetry, have ken synthesized. The larger pore M41S materials typically have surface areas above 700 m2/g and hydrocarbon sorption capacities of 0.7 cc/g and greater. A templating mechanism (liquid crystal templating-LCT) in which surfactant liquid crystal structures serve as organic templates is proposed for the formation of these materials. In support of this templating mechanism, it was demonstrated that the structure and pore dimensions of MCM-41 materials are intimately linked to the properties of the surfactant, including surfactant chain length and solution chemistry. The presence of variable pore size MCM-41, cubic material, and other phases indicates that M41S is an extensive family of materials.
10,349 citations
TL;DR: In contrast to heterogeneous Ziegler-Natta catalysts, homogeneous metallocene-based catalysts as discussed by the authors allow efficient control of regio-and stereoregularities, molecular weights and molecular weight distributions, and comonomer incorporation.
Abstract: Current studies on novel, metallocenebased catalysts for the polymerization of α-olefins have far-reaching implications for the development of new materials as well as for the understanding of basic reaction mechanisms responsible for the growth of a polymer chain at a catalyst center and the control of its stereoregularity. In contrast to heterogeneous Ziegler–Natta catalysts, polymerization by a homogeneous, metallocene-based catalyst occurs principally at a single type of metal center with a defined coordination environment. This makes it possible to correlate metallocene structures with polymer properties such as molecular weight, stereochemical microstructure, crystallization behavior, and mechanical properties. Homogeneous catalyst systems now afford efficient control of regio- and stereoregularities, molecular weights and molecular weight distributions, and comonomer incorporation. By providing a means for the homo- and copolymerization of cyclic olefins, the cyclopolymerization of dienes, and access even to functionalized polyolefins, these catalysts greatly expand the range and versatility of technically feasible types of polyolefin materials.
For corrigendum see DOI:10.1002/anie.199513681
2,436 citations
TL;DR: The unique structure of MCM-41 silicates has provided for extremely attractive properties such as uniform pore sizes greater than 20 A, surface areas exceeding 1000 m2 g−1, and long-range ordering of the pores.
Abstract: The unique structure of MCM-41 silicates (shown in the picture) has provided for extremely attractive properties—uniform pore sizes greater than 20 A, surface areas exceeding 1000 m2 g−1, and long-range ordering of the pores. Recent research in supramolecular-templated mesoporous materials has led to a wide range of compositions, to uses in a variety of catalytic reactions, and to a better control of bulk morphologies.
1,923 citations
TL;DR: Even late transition metal complexes function as active and selective catalysts for α-olefin polymerization, and an intense search has developed for new-generation catalysts, in both academic and industrial research laboratories.
Abstract: Even late transition metal complexes function as active and selective catalysts for α-olefin polymerization. The discovery of a highly active family of catalysts 1 based on iron, a metal that had no previous track record in this field, has highlighted the possibilities for further new catalyst discoveries. As a result, an intense search has developed for new-generation catalysts, in both academic and industrial research laboratories. R1=H, Me; R2=Me, iPr; R3=H, Me, iPr; R4=H, Me; X=halide.
1,737 citations