Chemistry and Chemical Biology ETDs

Publication Date

2-9-2010

Abstract

A novel set of lanthanide (Ln) alkoxycarbonates, [Ln(μ-CO2-DBP)(DBP)2]2 where Ln = lanthanide; and DBP = OC6H3-2,6-C(CH3)3, were isolated from a systematic study of the insertion of CO2(g) (referred to as CO2) into the Ln-O bonds of a series of new lanthanide alkoxides, Ln(OR)3. This study was undertaken to determine if the deleterious metal carbonate [M(CO3)y] formation that promotes higher thermal budgets during processing could be avoided. While processing controls can reduce the formation of the M(CO3)y phases, this is not always effective, and preventing the formation of these phases is of interest. Since CO2 insertion into transition metal alkoxides has been extensively studied and many structures reported, this research focused on CO2 insertion into the less-studied Ln-O bonds of Ln(OR)3. Initially a series of lanthanide amides [Ln(NR2)3 where R = SiMe3 and Ln = Ce (1), Sm (2), Dy (3), Yb (4), and Lu (5)] were synthesized following established routes.4-6 Subsequent conversion of the Ln(NR2)3 species into a series of Ln(OR)3 was achieved by an amide/alcohol exchange route resulting in Ln(DBP)3 (Ln = Ce (6), Sm (7), Dy (8), Yb (9), and Lu (10); DBP = 2,6-di-tert-butylphenoxide).7, 8 Once isolated, CO2 at low pressure (<5 psig) and ambient temperature was introduced to the Ln(OR)3 species to form a novel family of lanthanide alkoxycarbonate compounds identified as [Ln(\xb5- O2C-DBP)(DBP)2]2 (Ln = Ce (11), Sm (12), Dy (13), Yb (14), and Lu (15)). Surprisingly, CO2 did not insert into all of the Ln-O bonds, indicating that this process might be more controllable than initially expected. Higher-pressure CO2 experiments yielded the same carbonate compounds. Further manipulation of the ligand set, as a means to control CO2 insertion, was explored by using a mixed amide/alkoxide precursor generated in situ. This resulted in the formation of an unusual complex, Sm4(μ-CO3)2μ-O)2(DBP)4(THF)2(μ-DBP) (16). From this fundamental study, it has been shown that the ligand may be able to impact the degree of CO2 insertion into Ln-O bonds. The synthesis and characterization of 1 - 16, as well as future implications of this work, will be discussed in detail.

Language

English

Keywords

metal alkoxides, metal carbonates

Document Type

Thesis

Degree Name

Chemistry and Chemical Biology

Level of Degree

Masters

Department Name

Department of Chemistry and Chemical Biology

First Committee Member (Chair)

Kirk, Martin

Second Committee Member

Grey, John

Third Committee Member

Boyle, Timothy

Fourth Committee Member

Kemp, Richard

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