Scandium complexes applications

Additional catalytic investigation of p-diketiminate scandium complexes by Piers and coworkers showed that well-characterized complexes 121 and 122 with the bulky ligand L27 were highly active catalysts for intramolecular hydroamination to form nitrogen heterocycles. The catalytic reaction was monitored by determining starting material and product with NMR. Both the neutral complex 121 and the CIP complex 122 are effective catalysts (10 mol%) for the intramolecular hydroamination of 5-phenyl-4-pentyl-l-amine (R = H, R = Ph, n = 1 in Scheme 42). However, they are not active catalysts for the potential application to the intermolecular hydroamination of 1-hexyne with alkylamines [82],... 

The scandium complex 30 disclosed by Shapiro and co-workers (97), which represents the first application of the bridging amido-Cp ligand in metallocene chemistry, is imusual in its moderate ability to polymerize larger olefins such as 1-pentene. A yttrium analogue initiates polymerization of -butyl acrylate and acrylonitrile at room temperature and below (98). In the bis-Cp systems, a bridging group seems to improve reactivity toward a-olefins (99). The yttrocene dimer 31 produces highly isotactic polypropylene (Pmmmm = 97%) (100). 

Chiral scandium-bis(oxazolinyl)pyridine (Sc-pybox) complexes catalyze various catal5dic asymmettic addition reactions with carbonyl compounds. The first report of this complex was addition and annulation reactions of allenylsi-lanes with etiiyl glyoxylate using the scandium complex. The application of these complexes was expanded to various catalytic asymmetric transformations such as aldol reactions, allylation, and ene reactions. ... 

Simple bis(oxazoline) ligands, especially azabis(oxazolines), can catalyse the addition of indoles to benzylidene malonates in up to 99% ee, provided that excess of the chiral ligand is avoided.166 The paradigm followed in many asymmetric catalytic reactions that an excess of the chiral ligand with respect to the metal should improve enantioselectivity because the background reaction catalysed by a free metal is suppressed, was shown not to be applicable here,166 which might call for revisiting some of the many copper(II)-bis(oxazoline)-catalysed processes known. Enantioselective additions of pyrroles and indoles to ,/9-unsaturated 2-acylimidazoles catalysed by the bis(oxazolinyl)pyridine-scandium(III) triflate complex have been accomplished.167... 

It is a commonplace to say that there has been explosive growth in the use of lanthanides in organic chemistry. For many years, the use of cerium(iv) compounds as oxidants was widespread, but more recently a whole range of other compounds have made their appearance. Thus samarium(ii) compounds are now routinely used as one-electron reducing agents and the use of trifluoromethanesulfonate ( triflate ) salts of scandium and the lanthanides as water-soluble Lewis acid catalysts is widespread. Beta-diketonate complexes and alkoxides have also come into use there are even applications of mischmetal in organic synthesis. 

Non Rare Earth SATs. Several candidates that meet these criteria have been found, and some of their applications are discussed by Kruger (5). Krugers discussion also contains an excellent accoimt of the early history of this field. In a series of experiments at the Pennsylvania State University, Jester and coworkers (6,7) have used Br" and I" to mimic the movement of soluble species in natural waters. In-EDTA complexes have been used by Behrens et al. (8) to monitor groundwater movement, while Dahl (9) has shown that In(N03)2 could be used to trace water stream patterns and pollutant dispersal in and around the harbor of a Norwegian town. Indium and scandium were used as stable activable tracers for monitoring in-plant movements of water in waste water treatment plants by Craft and Eicholz (10). The entire subject of industrial uses of activable tracers has been reviewed recently by Van Dalen and Wijkstra (II). 

Additional work has described the use of copper, zinc and rare earth metals for halogenation reactions of chelating substrates. These reactions include another application of ligand 6, which in a screening revealed high enantioselectivities for zinc, scandium and copper complexes, with the former one as the best. Hence, preformed zinc complexes of 6 showed good performances in chlorination and fluorination reaction of 3-keto phosphonates [43] (Scheme 14). 

This chapter is devoted to the most significant developments of early-transition metal compounds ligated by N-heterocyclic carbene ligands (from group 3 to group 7 scandium to rhenium) [10]. When appropriate and available, the structural features of these metal complexes will be discussed. The synthetic pathways, bonding nature of the Ccarbene-M> reactivity, and applications of such derivatives (with a special emphasis on their use in catalysis) will be discussed [11]. 

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