Abstract
The reactions of organolithium reagents with the tetravalent UCl2[N(SiMe3)(2)](2) and its DME solvate have been examined. Treatment of both compounds with methyl-lithium in diethyl ether resulted in one electron reduction of the metal center and gamma-deprotonation of one of the ligands. The dimeric {U[(mu-CH2-SiMe2)N(SiMe3)](2)[mu-Li(DME)])(2) (1) was isolated from the reaction mixture regardless of the amount of MeLi employed. The employment of LiCH2SiMe3 in DME led instead to multiple gamma-deprotonation events at the same carbon atom with formation of the trimetallic [U[(mu-CH2SiMe2)N(SiMe3)][N(SiMe3)(2)]}(2)]UKH3-C-SiMe2)N(SiMe3)][N(SiMe3)2]{mu-OMe[ (2) cluster centered on a fully deprotonated carbon atom. Crystallographic analysis revealed the presence of mu-OCH3 units in the cluster as generated by DME solvent cleavage. A similar reaction carried out in the absence of DME led to the isolation of a closely related trimetallic [U mu-(CH2-SiMe2)N(SiMe3)][N(SiMe3)(2)]}(2){U[mu-C-SiMe2)N(SiMe3)][(p-CH2-SiMe2)N(SiMe3)]} (3). One additional y-deprotonated fragment replacing the bridging methoxy group of 2 was present in this case. The presence of a fully deprotonated carbon atom bridging three metal centers and of one silicon atom was confirmed by both X-ray structures and NMR data. An attempt to reduce UCl2[N(SiMe3)(2)](2) with KC8 in a coordinating solvent resulted in ligand scrambling with the formation of two products. The first is a trimeric U(III) cluster formulated as [U-p-CI[N(SiMe3)(2)][DMED2[U-R-CIIN(SiMe3)(2)](2)]{mu(3)-Cl}(2) (4). The second was U[N(SiMe3)(2)](3). A similar reduction reaction carried out in noncoordinating toluene resulted instead in an attack on the ligand affording the dimeric [U-mu-CI[N(SiMe3)(2)](2)]=N(SiMe3)]}(2) (5). Alkylation of UCl2[N(SiMe3)(2)](2) with n-butyl-lithium in hexane surprisingly yielded the pentavalent U[mu-CH2-SiMe2)N(SiMe3)](2)[N(SiMe3)(2)] (6). The acquisition of one additional ligand during the reaction hinted at the presence of other products in the reaction mixture.