Synthesis and structure of organosamarium metallocenes including the carbon-hydrogen and carbon-carbon bond cleavage reactivity of unsolvated tris(pentamethylcyclopentadienyl) samarium complexes

This dissertation describes advances in several areas of lanthanide metallocene chemistry including the reactivity of the sterically crowded tris(pentamethylcyclopentadienyl) samarium complex (C5Me5)3Sm, C-H and C-C bond activation reactivity of unsolvated metallocene alkyl complexes [(C 5Me5)2LnR]x, and the reactivity of metallocene hydrides [(C5Me5)2LnH]x with trialkyl boranes related to their potential use as catalysts in the conversion of borates to boranes in hydrogen fuel recycling schemes.; The first chapter of this dissertation investigates (C5Me 5)3Sm reactivity with radical clocks and free radical reagents including 2,2,6,6-tetramethylpiperidinyl-1-oxy (TMPO) to evaluate a new type of metallocene reduction process called Sterically Induced Reduction.; In the second chapter, a cyclopentadienyl ligand containing a tethered olefin is used to examine weak lanthanide metal-olefin interactions in metallocene coordination environments. The X-ray crystal structures of divalent samarium and ytterbium [(C5Me4)SiMe2(CH2CH = CH2)]2Ln were shown to be isomorphous and similar to Eu in olefin orientation toward the metal center.; The third chapter of this dissertation describes the synthesis, structure, and C-H activation reactivity of unsolvated lanthanocene alkyl complexes, [(C5Me5)2LnR]x. The loosely ligated [BPh4]1- ion in [(C5Me5) 2Ln][(mu-Ph)2BPh2] can be readily displaced by alkyl lithium or potassium reagents to provide access to the corresponding unsolvated alkyl lanthanide metallocenes.; Chapter four describes the formation of a bridging planar trimethylenemethane dianion complex, [(C5Me5)2Sm]2[mu-eta 3: eta3-C(CH2)3] from a reaction of neopentyllithium and [(C5Me5)2Ln] [(mu-Ph) 2BPh2]. Formation of the [C4H6] 2- trimethylenemethane ligand from the [C5H 11]1- neopentyl precursor can be explained by a combination of a beta-methyl elimination reaction to form isobutene and [(C5Me5)2SmMe]3, with subsequent C-H activation reactions.; Chapter five of this dissertation evaluates the efficacy of a stable silylene (R2Si:) to function as a 2 electron donor ligand to the divalent lanthanide metal center in decamethylsamarocene (C5Me 5)2Sm.; The sixth chapter is concerned with the potential use of NaBH4 as a viable medium for hydrogen storage and delivery in the hydrogen fuel cell economy. Reactivity of the hydrides [(C5Me5) 2LnH]2 (Ln = La, Sm, Y), with BEt3 is discussed including the unusual solid state structures of (C5Me5) 2La{lcub}(mu-H)[(mu-H)CHMe]2BEt{rcub}, and its THF solvate, (C 5Me5)2La(THF){lcub}(mu-H)[(mu-H)2CMe]BEt 2{rcub} which involve La ligation by the hydrogen atoms of the ethyl groups. (Abstract shortened by UMI.)...