The reduction chemistry of the LnZ(3)/alkali metal system: Synthesis, characterization, and reactivity studies of lanthanide dinitrogen complexes

This dissertation describes the discovery of new methods of lanthanide reduction chemistry that extend beyond the traditional divalent Ln2+ approaches and offer new opportunities in developing f element chemistry. This research has resulted in the discovery of new f element reaction chemistry, the development of new synthetic strategies to synthesize dinitrogen complexes, and the first information on the reaction chemistry of [(C5Me5)2(THF)Ln]2(μ-η 2:η2-N2) compounds.;Chapter 1 describes how the LnZ3/K reduction system, Ln[N(SiMe 3)2]3/potassium graphite reacts with N2 in THF to form the dinitrogen complexes {[(Me3Si)2N] 2(THF)Ln}2(μ-η2:η2-N 2) (Ln = Y, Ho, Tm, and Lu). The Ln[N(SiMe3)2] 3/K reduction of dinitrogen provides access from readily available starting materials to the formerly rare class of M2(μ-η2:η 2-N2) complexes, {[(Me3Si)2N] 2(THF)Ln}2(μ-η2:η2-N 2), that had previously been made only from the highly reducing TmI 2, DyI2, and NdI2 in the presence of KN(SiMe 3)2. The Y and Lu complexes made via LnZ3/K are the first diamagnetic complexes of this type.;In Chapter 2, exploration of the LnZ3/K dinitrogen reduction system with the entire lanthanide series and Z = [N(SiMe3) 2] is described. This study examined the generality of this reaction and explored the correlation of the observed reactivity with accessibility of divalent oxidation states.;In Chapter 3, the extension of the LnZ3/K reduction system to organometallic compounds using Z = C5Me4H is described. This approach showed that the LnZ3/K reduction system is not limited to Z = [N(SiMe3)2], but can be extended to the (C 5Me4H)3Ln, Ln = La and Nd. In addition, it was found that heteroleptic precursors like [(C5Me5) 2La][BPh4] could also be used. The syntheses also provided another advance in that the yield of the reduced dinitrogen products was high.;In Chapter 4, synthesis of the previously inaccessible, smallest member of the (C5Me4H)3Ln series, (C5Me 4H)3Lu, from [(C5Me4H)2Lu][(μ-Ph) 2BPh2] and KC5Me4H is presented. This complex is reduced with potassium under dinitrogen to form [(C5Me4H) 2(THF)Lu]2(μ-η2:η2-N 2).;Chapter 5 shows that the [(C5Me5)2(THF)Ln] 2(μ-η2:η2-N2) complexes are strong reductants in their own right and provide another option in reductive lanthanide chemistry. Lanthanide-based reduction chemistry can be effected in a diamagnetic trivalent system using the dinitrogen reduction product, [(C5Me5)2(THF)La]2(μ-η 2:η2-N2). Using this reductive approach with CO generates a ketene carboxylate moiety, (O2C-C=C=O) 2-, via complete scission and reductive homologation of CO.