Tetrakis[lithium-tert-butyl(di-tert-butylfluorosilyl)amide]-dilithium oxide, (tBu2SiF–NLitBu)4Li2O—a Li6O4+-cluster

Di-tert-butylfluorosilyl-tert-butylamine is converted into the lithium derivative (tBu2SiFLiNtBu)2 (1) by n-BuLi. Compound 1 forms a dimer via the LiN bond in non-polar solvents like n-hexane. In the reaction of 1 and Et2O the ether adduct (tBu2SiFLiNtBu)2OEt2 (2) is formed. Compound 2 crystallised as a bicyclic compound with four-coordinate lithium in a F2Li(OEt2)N unit and two-coordinate lithium in a NLiN unit. In the presence of trace quantities of water, which can account for its central oxo anion, or in the presence of atmospheric moisture the title compound tetrakis(lithium-di-tert-butylfluorosilylamide)-dilithium oxide, (tBu2SiF–NLitBu)4Li2O, (3) is formed. The heteroatom core of 3 consists of four (OLiNLi) four-membered and four (OLiFSiNLi) six-membered rings. This presents a new mode for fluorosilylamide coordination to lithium.