Imidazolin-2-iminato ligands are regarded as 2σ, 4π electron donors, leading to strong metal nitrogen bonds, with a higher M-N bond order, presenting a highly attractive ligand class for actinides. When an acid-base reaction is carried out between the homoleptic uranium (IV) amido complex [U(NMeEt)4] and the neutral imidazolin-2-imine ImRNH, the product [(ImRN)nU(NMeEt)4-n] (I) depends on the steric demand of the imidazolin-2-iminato ligand regardless of the reaction conditions, indicating a thermodynamic control of the reaction. In order to selectively obtain mono(imidazolin-2-iminato) actinide (IV) complexes (II), a protonolysis of the actinide metallacycles [{(Me3Si)N}2An{k2C,N-CH2SiMe2N(SiMe3)}] with imidazolin-2-imines ImRNH was performed. Moreover, mixed cyclopentadienyl imidazolin-2-iminato actinide complexes (III) could be obtained by a protonolysis reaction of [Cp*2AnMe2] with imidazolin-2-imines. The imidazolin-2-iminato actinide complexes prepared displayed short An-N bond lengths and large, close to linear An-N-C bond angles, indicating a substantial π-character to the An-N bond. Normally, it is well expected that due to their oxophilicity, actinide complexes will be very prompt to form oxygen-metal bonds precluding actinide complexes to be active catalysts with oxygen containing substrates. A possible way to overcome this challenge is by coordination of highly nucleophilic imidazolin-2-iminato ligands, which are expected to slightly increase the electron density of the electrophilic metal center, decreasing the oxophilicity of the respective actinide complex and making it an active catalyst towards oxygen containing substrates. The reactivity of the thorium (IV) complex [(ImDippN)Th{N(SiMe3)2}3] towards aldehydes was studied in the catalytic Tishchenko reaction, displaying a high activity, even at room temperature. Moreover, the asymmetrically substituted esters could be obtained selectively in the crossed Tishchenko reaction between aromatic and cyclic or branched aliphatic aldehydes.

Increasing the reactivity of actinide coordination compounds: Imidazolin-2-iminato actinide complexe

249th National Meeting (2015)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.