Nucleophilic Reactivity of a Nitride-Bridged Diuranium(IV) Complex: CO2 and CS2 Functionalization

Abstract

Thermolysis of the nitride-bridged diuranium(IV) complex Cs{(μ-N)[U(OSi(O(t) Bu)3)3]2} (1) showed that the bridging nitride behaves as a strong nucleophile, promoting N-C bond formation by siloxide ligand fragmentation to yield an imido-bridged siloxide/silanediolate diuranium(IV) complex, Cs{(μ-N(t) Bu)(μ-O2 Si(O(t) Bu)2)U2 (OSi(O(t) Bu)3)5}. Complex 1 displayed reactivity towards CS2 and CO2 at room temperature that is unprecedented in f-element chemistry, affording diverse N-functionalized products depending on the reaction stoichiometry. The reaction of 1 with two equivalents of CS2 yielded the thiocyanate/thiocarbonate complex Cs{(μ-NCS)(μ-CS3 )[U(OSi(O(t)Bu)3)3]2} via a putative NCS(-)/S(2-) intermediate. The reaction of 1 with one equivalent of CO2 resulted in deoxygenation and N-C bond formation, yielding the cyanate/oxo complex Cs{(μ-NCO)(μ-O)[U(OSi(O(t) Bu)3 )3]2}. Addition of excess CO2 to 1 led to the unprecedented dicarbamate product Cs{(μ-NC2O4)[U(OSi(O(t) Bu)3)3]2}.

Keywords: carbon dioxide; carbon disulfide; cyanates; nitrides; uranium.