Metallocene Organoactinide Complexes

During the last decade, the chemistry of d0/fn actinides has flourished reaching a high level of sophistication. Compared to the early or late transition-metal complexes and lanthanides, the actinides sometimes exhibit parallel but mostly complementary activities for similar organic processes, and sometimes even challenge the activities of the transition metals. A rapid increase in the numbers of reports in the Cambridge database also reflects their current importance. In view of the above, in this particular review we have provided an overview and updated information about the preparation and properties of the major classes of actinide complexes containing different cyclopentadienyl ligands and having the oxidation states (+3 and +4)

Selective Actinide-Catalyzed Tandem Proton-Transfer Esterification of Aldehydes with Alcohols for the Production of Asymmetric Esters

Actinide-catalyzed tandem proton-transfer esterification between aldehydes and alcohols is presented herein for the first time. It represents a novel convenient and external-oxidant-free methodology in the preparation of asymmetric ester compounds. Various kinds of aldehydes and alcohols can be applied to this reaction, affording the corresponding ester product in moderate to high yields. A plausible mechanism was proposed on the basis of the kinetic, stoichiometric, and deuterium-labeling studies

Catalytic Organic Transformations Mediated by Actinide Complexes

This review article presents the development of organoactinides and actinide coordination complexes as catalysts for homogeneous organic transformations. This chapter introduces the basic principles of actinide catalysis and deals with the historic development of actinide complexes in catalytic processes. The application of organoactinides in homogeneous catalysis is exemplified in the hydroelementation reactions, such as the hydroamination, hydrosilylation, hydroalkoxylation and hydrothiolation of alkynes. Additionally, the use of actinide coordination complexes for the catalytic polymerization of α-olefins and the ring opening polymerization of cyclic esters is presented. The last part of this review article highlights novel catalytic transformations mediated by actinide compounds and gives an outlook to the further potential of this field

Bis(imidodithiodiphosphinato) Titanium and Zirconium Complexes: Synthesis, Characterization, and Their Catalytic Activity in the Polymerization of alpha-Olefins

The synthesis, characterization, and low-temperature crystal structures of a family of group 4 complexes containing different numbers of imidodithiodiphosphinate ligands and different metal oxidation states is presented. Their catalytic activity in the polymerization of ethylene and propylene was studied. For ethylene, when these complexes are activated with methylalumoxane (MAO), they are active catalysts in the polymerization producing extremely high molecular weight, high-density polyethylene with very narrow polydispersities. However, for propylene, the activity of these complexes is low, producing only atactic polypropylene. The bis(imidodithiodiphosphinate)titanium(bis(amido)) complex 6e has a singular reactivity, which upon heating forms the corresponding imido complex with the concomitant elimination of Et3N and the formation of the homoleptic complex tris(imidodithiodiphosphinate)titanium(III) (6h).</p

Mono(imidazolin-2-iminato) Hafnium Complexes: Synthesis and Application in the Ring-Opening Polymerization of <i>ε</i>-Caprolactone and <i>rac</i>-Lactide

Mono-substituted imidazolinX-2-iminato hafnium(IV) complexes (X = iPr, tBu, Mesityl, Dipp) were synthesized and fully characterized, including solid-state X-ray diffraction analysis. When the X group is small (iPr), a dimeric structure is obtained. In all the monomeric complexes, the Hf-N bond can be regarded as a double bond with similar electronic properties. The main difference among the monomeric complexes is the cone angle of the ligand, which induces varying steric hindrances around the metal center. When the monomeric complex of mono(bis(diisopropylphenyl)imidazolin-2-iminato) hafnium tribenzyl was reacted with three equivalents (equiv) of iPrOH, the benzyl groups were easily replaced, forming the corresponding tri-isopropoxide complex. However, when BnOH was used, dimeric complexes were obtained. When five equivalents of the corresponding alcohols (BnOH, iPrOH) were reacted with the monomeric complex, different dimeric complexes were obtained. Regardless of the high oxophilicity of the hafnium complexes, all complexes were active catalysts for the ring-opening polymerization (ROP) of ε-caprolactone. Dimeric complexes 5 and 6 were found to be the most active catalysts, enabling polymerization to occur in a living, immortal fashion, as well as the copolymerization of ε-caprolactone with rac-lactide, producing block copolymer PCL-b-LAC. The introduction of imidazolin-2-iminato ligands enables the tailoring of the oxophilicity of the complexes, allowing them to be active in catalytic processes with oxygen-containing substrates