Rigid NON- and NSN-ligand complexes of tetravalent and trivalent uranium: comparison of U-OAr2 and U-SAr2 bonding.

A rigid NSN-donor proligand, 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylthioxanthene (H(2)[TXA(2)], 1) was prepared by palladium-catalyzed coupling of 2,6-diisopropylaniline with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylthioxanthene. Deprotonation of 1 using (n)BuLi provided Li(2)(DME)(2)[TXA(2)] (2), and subsequent reaction with UCl(4) afforded [Li(DME)(3)][(TXA(2))UCl(3)] (4). The analogous NON-donor ligated complex [(XA(2))UCl(3)K(DME)(3)] [3; XA(2) = 4,5-bis(2,6-diisopropylanilino)-2,7-di-tert-butyl-9,9-dimethylxanthene] was prepared by the reaction of K(2)(DME)(x)[XA(2)] with UCl(4).

Acyclic boron-containing π-ligand complexes: η2- and η3-coordination modes.

Cyclic boron-containing π-ligands such as boratabenzenes and borollides are well established, in particular as supporting ligands. By contrast, the chemistry of acyclic boron-containing π-ligands has remained relatively unexplored, presumably in part due to the higher reactivity of acyclic π-ligands relative to cyclic analogues. This perspective is focused on the synthesis, structures and reactivity of isolated transition metal complexes bearing η(n)-coordinated (n = 2 or 3) acyclic boron-containing ligands.