Expanding the limits of lanthanide metallocenes to advance catalysis, inert bond activation, redox, and heterocyclic chemistry

The pentamethylcyclopentadienyl ligand, (C5Me5) 1-, has played an important role in exploring highly reactive f-element organometallic chemistry. In particular, lanthanides ligated with two of these ligands to form (C5Me5)2Ln metallocene moieties have been exceptional at stabilizing unusual and unexpected complexes. This dissertation expands the breadth of lanthanide C5Me5 chemistry in several areas including (a) modeling the generation of isoprene polymerization catalysts with the carboxylate complex, [(C5Me 5)2Sm(mu-O2CPh)]2, (b) C-H and C-C bond activation with unsolvated lanthanide alkyls, [(C5Me 5)2LnR]x, and hydrides, [(C5Me 5)2LnH]x, (c) C-H bond activation, sterically induced reduction chemistry, and eta1-alkyl-like reactivity with (C5Me5)3Ln complexes, (d) synthesis and versatile reactivity with divalent (C5Me5)Ln(mu-eta 6:eta1-Ph)2BPh2 complexes, and (e) Me3SiCHN2 chemistry with lanthanide metallocene complexes ultimately leading to heterocyclic ring compounds.;The first three chapters of this dissertation describes the reaction chemistry of a model carboxylate complex, [(C5Me5) 2Sm(mu-O2-CPh)]2, and alkylaluminum reagents related to lanthanide-based isoprene polymerization. (C5Me 5)2Sm(THF)(mu-eta2:eta1-EtAlEt 3), a complex that displays an unusual (mu-eta2-:eta 1-Et) coordinated ligand in its solid state X-ray crystal structure, is among the unexpected products discussed in the first chapter. In the second chapter, a samarocene ethyl-aluminum oxide (EAO) complex, [(C5Me 5)2Sm]2[(mu-Et)4Al4Et 6O2], derived from [(C5Me5)2Sm(mu-O 2CPh)]2 and AlEt3 is discussed. In contrast, a mixed-bridged bimetallic complex, [(C5Me5)2Sm(mu-O 2CPh)(mu-iBu)Al(iBu)2], is isolated from [(C5Me5)2Sm(mu-O2CPh)] 2 with AliBu3 that has two different isomers in a single crystal and is described in the third chapter.;The fourth chapter describes the synthesis, structure, and reactivity of the bridging planar trimethylenemethane (TMM) complexes, [(C5Me 5)2Ln]2[mu-eta3:eta 3-C(CH2)3], (Ln = La, Pr, Nd, and Y). Both X-ray crystallographic data and DFT calculations on these complexes are consistent with a planar [C(CH2)3]2- moiety with little to no covalent bonding component. [(C5Me5) 2Sm]2[mu-eta3:eta3-C(CH 2)3] reacts with two equiv of Ph2CO expanding the TMM unit to a bis-alkoxide ligand, [(OCPh2CH2) 2C=CH2]2-.;In the fifth chapter, the chemistry of sterically crowded tris(pentamethylcyclopentadienyl) complexes, (C5Me5)3M, is expanded to M = Ce, Pr, Gd, and Y. These complexes have the longest M-C(C5Me 5) bond distances ever reported for these metals. A comparative study between the larger and smaller metals of the (C5Me5) 3M complexes shows that the (C5Me5)1- ligand participates in eta1-alkyl-like reactivity, sterically induced reduction, and C-H bond activation of arenes.;The sixth chapter is an attempt to synthesize the most sterically crowded (C5Me5)3Ln complex of the smallest lanthanide: lutetium. A rare lanthanide vinyl complex, (C5Me5) 2Lu(CH=C5Me4), was isolated as a result of C-H bond activation of tetramethylfulvene (TMF). The second product, a "tuck-over" complex, (C5Me5)2Lu(mu-H(mu-eta 1:eta5-CH2C5Me4)Lu(C 5Me5), has also been characterized. The possibility of a "(C5Me5)3Lu" intermediate is presented.;The seventh chapter introduces a new class of divalent mono(pentamethylcyclopentadienyl) lanthanide tetraphenylborate complexes, (C5Me5)Ln(mu-eta 6:eta1-Ph)2BPh2. The unsolvated precursors, (C5Me5)2Ln, were obtained in high yield from the solvated complexes, (C5Me5) 2Ln(THF)2, without sublimation. The THF solvation of (C 5Me5)Ln(mu-eta6:eta1-Ph) 2BPh2 complexes revealed variable (BPh4) 1- coordination in the complexes, [(C5Me 5)Ln(THF)x][BPh4] and (C5Me5)Sm(mu-eta 6:eta1-Ph)(mu-eta1:eta 1-Ph)BPh2(THF).;In the eighth chapter, the reduction, ligand redistribution, and ionic metathesis reaction chemistry of the (C5Me5)Ln(mu-eta 6:eta1-Ph)2BPh2 complexes is described. Reduction of 1,3,5,7-cyclooctatetraene, C8H8, and phenazine, C12H8N2, resulted in ligand redistributed products while the reaction with PhN=NPh provided the azobenzenc radical anion complex, (C5Me5)(BPh4)Sm(N 2Ph2). Ionic metathesis with KN(SiMe3)2 formed the divalent heteroleptic complex, {(C5Me5)Yb[(mu-N(SiMe 3)2]}2.;The ninth chapter presents a number of structurally characterized mono(pentamethylcyclopentadienyl) lanthanide complexes that add to the paucity of data in this field and illustrate the complexity of mono(C5Me5) lanthanide chemistry.;In the tenth chapter, the reactivity of the diazoalkane, Me3SiCHN 2, with various samarocene complexes is described. The reactions form an isocyano-trimethylsilyl bimetallic complex. {(C5Me5) 2Sm[mu-N(SiMe3)NC]}2, that reacts with MeCN to form the 1,3,4-triazole anion complex, {(C5Me5) 2Sm[mu-eta1:eta2- NCNN&parl0;SiMe3&parr0;C (Me)]}2. This represents a new method for lanthanide-based heterocyclic ring synthesis.