412344-08-2Relevant articles and documents
Cationic scandium methyl complexes supported by a β-diketiminato ( Nacnac ) ligand framework
Hayes, Paul G.,Piers, Warren E.,McDonald, Robert
, p. 2132 - 2133 (2002)
The base-free dimethyl scandium complex supported by the bulky β-diketiminato ligand ArNC(tBu)CHC(tBu)NAr (Ar = 2,6-iPr2C6H3, 1) reacts with various equivalencies of the strong organometallic Lewis acid B(C6F5)3 to give scandium alkyl cations. With 0.5 equiv, a monocationic μ-methyl dimer (2) was observed spectroscopically. Reaction with a further 0.5 equiv of borane gives the monomeric methyl cation 3, which was fully characterized, including via X-ray crystallography. This compound is fluxional on the NMR time scale via a ligand flip mechanism. Reaction with another equivalent of borane gives the unique dication 4, which exhibits a static structure on the NMR time scale. Dimethyl compound 1 is a highly active catalyst precursor for ethylene polymerization under borane or MAO-type activation. Activities for this group 3 metal based catalyst approach those observed for group 4 based metallocene systems. Copyright
Reactivity of scandium β-diketiminate alkyl complexes with carbon dioxide
Leblanc, Francis A.,Berkefeld, Andreas,Piers, Warren E.,Parvez, Masood
, p. 810 - 818 (2012/04/17)
The reactions of two highly air- and moisture-sensitive scandium bis(alkyls) supported by a bulky β-diketiminato (nacnac) ligand with carbon dioxide are described. [κ2-ArNC(tBu)CHC( tBu)NAr]ScR2 (Ar = 2,6-iPr2C 6H3; R = CH3, 1a; R = CH2SiMe 3, 1b) react rapidly with CO2 to give mixtures of mono- and bis(carboxylato) insertion products 2a/2b and 3a/3b depending on the stoichiometry and conditions of the reaction. Compound 2a (R = CH3) is a dimeric complex with bridging acetato groups, as determined by X-ray crystallography. These compounds were characterized by NMR spectroscopy, and 3a could be isolated in pure form. Treatment of these compounds with excess CO 2 resulted in addition to the central carbon of the Sc(nacnac) six-membered ring and displacement of the nitrogen donors to yield dimeric scandium carboxylates 4a/4b; compound 4b was characterized by X-ray crystallography. Reactions of the nacnac scandium cations formed upon abstraction of one or two methides from 1a using B(C6F 5)3 with CO2 were also explored. Although the products were qualitatively more thermally robust, eventually ligand displacement occurred in these cationic acetato complexes as well. Nevertheless, insertion products were characterizable in solution using NMR spectroscopy. Overall, this study shows the facility with which CO2 is taken up by scandium alkyls but that the nacnac ligand framework is too reactive to support chemistry aimed at catalytic conversion of CO2 into other products.
