The coordination chemistry of the amidine ligand
TL;DR: In this article, a review of metal-metal bridging with the presence of the amidino group is presented, with a focus on bridging modes for the group and a reference to other aza-allyl systems.
About: This article is published in Coordination Chemistry Reviews.The article was published on 1994-07-01. It has received 631 citations till now. The article focuses on the topics: Coordination complex & Amidine.
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661 citations
TL;DR: Guanidines have attracted increasing attention as electronically and sterically flexible ligands as mentioned in this paper, exhibiting a variety of coordination modes and a range of donor properties leading to compatibility with a remarkably wide range of metal ions from all parts of the periodic table.
476 citations
TL;DR: Two plausible mechanistic pathways involving ketenimine or triazole intermediate are tentatively presented for the copper-catalyzed three-component coupling reactions.
Abstract: A highly efficient, mild, practical, and catalytic multicomponent reaction for the synthesis of N-sulfonylamidines has been developed. This reaction has an extremely wide scope with regard to all three coupling components of alkyne, sulfonyl azide, and amine. Two plausible mechanistic pathways involving ketenimine or triazole intermediate are tentatively presented for the copper-catalyzed three-component coupling reactions.
384 citations
TL;DR: This tutorial review covers the success story of lanthanide amidinates and guanidinates and their transition from mere laboratory curiosities to efficient homogeneous catalysts as well as ALD and MOCVD precursors.
Abstract: For decades, the organometallic chemistry of the rare earth elements was largely dominated by the cyclopentadienyl ligand and its ring-substituted derivatives. A hot topic in current organolanthanide chemistry is the search for alternative ligand sets which are able to satisfy the coordination requirements of the large lanthanide cations. Among the most successful approaches in this field is the use of amidinate ligands of the general type [RC(NR')(2)](-) (R = H, alkyl, aryl; R' = alkyl, cycloalkyl, aryl, SiMe(3)) which can be regarded as steric cyclopentadienyl equivalents. Closely related are the guanidinate anions of the general type [R(2)NC(NR')(2)](-) (R = alkyl, SiMe(3); R' = alkyl, cycloalkyl, aryl, SiMe(3)). Two amidinate or guanidinate ligands can coordinate to a lanthanide ion to form a metallocene-like coordination environment which allows the isolation and characterization of stable though very reactive amide, alkyl, and hydride species. Mono- and trisubstituted lanthanide amidinate and guanidinate complexes are also readily available. Various rare earth amidinates and guanidinates have turned out to be very efficient homogeneous catalysts e.g. for ring-opening polymerization reactions. Moreover, certain alkyl-substituted lanthanide tris(amidinates) and tris(guanidinates) were found to be highly volatile and could thus be promising precursors for ALD (= Atomic Layer Deposition) and MOCVD (= Metal-Organic Chemical Vapor Deposition) processes in materials science and nanotechnology. This tutorial review covers the success story of lanthanide amidinates and guanidinates and their transition from mere laboratory curiosities to efficient homogeneous catalysts as well as ALD and MOCVD precursors.
381 citations
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TL;DR: The body of this paper is devoted to further discussion, a more detailed consideration of the covalent radii, and a rather extensive but quite incomplete comparison of observed bond distances with the values given by the additivity rule and by Equation 1.
Abstract: The body of this paper is devoted to further discussion, a more detailed consideration of the covalent radii, and a rather extensive but quite incomplete comparison of observed bond distances with the values given by the additivity rule and by Equation 1.
490 citations
356 citations
TL;DR: In this paper, the mechanistic pathways in the catalytic carbonylation of methanol by rodium and iridium complexes were studied, and it was shown that the reaction rate is strongly dependent on water and carbon monoxide pressure.
Abstract: Publisher Summary The chapter focuses on the mechanistic pathways in the catalytic carbonylation of methanol by rodium and iridium complexes. Kinetic studies of the rhodium-catalyzed methanol carbonylation reaction show a remarkably simple behavior. The iodide promoter can be charged to the reaction in several different forms without marked differences in the reaction rate being noted. Many different types of rhodium compounds can be charged to the reaction, and at typical reaction temperatures of 1500–2000C, they function as effective catalysts. The generation of the initial metal–carbon bond in the catalytic cycle by reaction of methyl iodide with a metal carbonyl, containing species has been proposed as a key step in both the cobalt and rhodium catalyzed systems. Iridium is also an excellent homogeneous catalyst for the carbonylation of methanol under relatively mild reaction conditions. There are apparently complex interactions among solvent, water, iodide form, and carbon monoxide pressure, and this complicates interpretation. Some general kinetic observation can be studied as (1) the reaction rate is strongly dependent on water concentration, with a decrease in rate being observed at higher water levels; (2) in reaction media containing appreciable concentrations of iodide ion, the reaction rate increases with increasing carbon monoxide pressure; (3) the reaction rate is not first order with respect to methyl iodide concentration as in the rhodium system, but shows an optimum level; and (4) at low iodide levels using methyl acetate as the substrate with low levels of water present, the reaction rate is inversely dependent on carbon monoxide pressure.
198 citations
185 citations