Wenliang Huang

Scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand.

The synthesis and characterization of the first scandium arene inverted-sandwich complexes supported by a ferrocene diamide ligand (NN(fc)) are reported. Through the use of (NN(fc))ScI(THF)(2) as a precursor and potassium graphite (KC(8)) as a reducing agent, the naphthalene and anthracene complexes [(NN(fc))Sc](2)(μ-C(10)H(8)) and [(NN(fc))Sc](2)(μ-C(14)H(10)), respectively, were synthesized and isolated in moderate to high yields. Both molecular structures feature an inverted-sandwich geometry and exhibit short Fe-Sc distances. DFT calculations were employed to gain understanding of the electronic structures of these new scandium arene complexes. A variable-temperature NMR spectroscopic study of [(NN(fc))Sc](2)(μ-C(14)H(10)) indicated that two different structures are accessible in solution. Reactivity studies showed that the naphthalene complex [(NN(fc))Sc](2)(μ-C(10)H(8)) can be converted to the corresponding anthracene species [(NN(fc))Sc](2)(μ-C(14)H(10)) and that [(NN(fc))Sc](2)(μ-C(10)H(8)) can act as either a reductant or a proton acceptor. The reaction of [(NN(fc))Sc](2)(μ-C(10)H(8)) with excess pyridine led to a rare example of C-C bond formation between two pyridine rings at the para position.

Transmetalation reactions of a scandium complex supported by a ferrocene diamide ligand.

Efforts to transfer to aluminum the heterocyclic ligand of a ring-opened imidazole scandium complex, which was previously reported, are presented. A ring-opened imidazole aluminum compound was formed at 50 °C and characterized as a trialuminum complex. At high temperature (85 °C), the formation of an unusual scandium/aluminum methylidene was observed. The reaction products were characterized by standard spectroscopic techniques and X-ray crystallography. Density functional theory calculations were used to understand the electronic structure of the scandium/aluminum methylidene complex.

In situ synthesis of lanthanide complexes supported by a ferrocene diamide ligand: extension to redox-active lanthanide ions

Reliable transformation of low-cost rare-earth metal oxides to organometallic rare-earth metal complexes is a prerequisite for the advancement of non-aqueous rare-earth metal chemistry. We have recently developed an in situ method to prepare rare-earth alkyl and halide precursors supported by a diamidoferrocene NNTBS, 1,1′-fc(NSiMe2tBu)2, as an ancillary ligand. Herein, we extended the scope of this method to other lanthanide ions including those that are redox active, such as cerium, praseodymium, samarium, terbium, thulium, and ytterbium. Specifically, samarium trisbenzyl could be generated in situ and then converted to the corresponding samarium benzyl or iodide complexes in good yield. However, it was found that ytterbium trisbenzyl could not be formed cleanly and the consequent conversion to ytterbium iodide complex was low yielding. By adapting an alternative route, the desired ytterbium chloride precursor could be obtained in good yield and purity.

Rare-earth metal π-complexes of reduced arenes, alkenes, and alkynes: Bonding, electronic structure, and comparison with actinides and other electropositive metals

Rare-earth metal complexes of reduced π ligands are reviewed with an emphasis on their electronic structure and bonding interactions. This perspective discusses reduced carbocyclic and acyclic π ligands; in certain categories, when no example of a rare-earth metal complex is available, a closely related actinide analogue is discussed. In general, rare-earth metals have a lower tendency to form covalent interactions with π ligands compared to actinides, mainly uranium. Despite predominant ionic interactions in rare-earth chemistry, covalent bonds can be formed with reduced carbocyclic ligands, especially multiply reduced arenes.

CH Bond Activation of Hydrocarbons Mediated by Rare-Earth Metals and Actinides: Beyond σ-Bond Metathesis and 1,2-Addition

© 2015 Elsevier Inc. This review discusses C. H bond activation of hydrocarbons mediated by rare-earth metal complexes with an emphasis on type of mechanisms. The review is organized as follows: in the first part, C. H bond activations mediated by rare-earth metals and actinides following traditional reaction pathways, such as σ-bond metathesis and 1,2-addition, are summarized; in the second part, nontraditional C. H bond activation examples are discussed in detail in order to understand the underlying mechanisms. The scope of the review is limited to rare-earth metals and actinides, but, in some cases, closely related reactivity of group 4 metals will be included for comparison. The purpose of the review is not only to provide a brief overview of C. H bond activation by f-elements but also to bring to attention unusual C. H bond cleavage reactivity following mechanisms different than σ-bond metathesis and 1,2-addition.

CCDC 1009347: Experimental Crystal Structure Determination

Related Article: Wenliang Huang, Florian Dulong, Saeed I. Khan, Thibault Cantat, Paula L. Diaconescu|2014|J.Am.Chem.Soc.|136|17410|doi:10.1021/ja510761j