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The focus of the work presented here is the synthesis and study of complexes featuring tantalum-germanium triple bonds. Numerous transition metal complexes containing multiple bonds to germanium are known in the literature, however, while the ability of tantalum to form multiple bonds with main group elements is documented, no examples containing a tantalumgermanium double- or triple-bond are known. At the onset of this work, the earliest transition metals reported in tetrylidyne complexes involving the heavier elements (Si-Pb) were the Group-VI metals chromium, molybdenum, and tungsten. This provided further motivation for targeting tantalum-germylidyne complexes so as to move known germylidyne complexes to include earlier transition metals. The results presented in Chapters 2 and 3 of this work highlight, in particular, the ability of tantalum to form multiple bonds with germanium, and in two instances with tin, in both the tantalum(I) and (−I) oxidation states. This is quite fortuitous as to date no metal-tetrylidyne complexes have been reported in which the metal has a d4-electron configuration as in the tantalum(I) complexes. Furthermore, a new convenient pathway for the synthesis of this type of complex has been discovered and is described. As a final note, since the initiation of this work heavy tetrylidyne complexes of niobium and titanium have been reported. The remainder of the Introduction is organized into five sections. Section 1.1 summarizes what is known regarding tantalum-tetrel triple bonds, while Section 1.2 describes germaniumgermanium multiple bonding in the context of isolated molecules. The structures of the heavy alkenes and alkynes analogues, digermenes and digermynes, respectively, are contrasted with those of alkene and alkynes. For both the doubly-bonded and triply-bonded complexes the most prominent bonding models are provided along with literature insights gained from quantum chemical calculations. Section 1.3 presents the most common routes used to synthesize germylenes1, which were the germanium precursors used in this work for obtaining tantalum-germylidyne complexes. In Section 1.4 an overview of the two most commonly employed methods for synthesizing germylidyne complexes is provided in which the merits and drawbacks of each are summarized. Section 1.5 provides a brief introduction to the bonding model often invoked when describing the triple-bond between a metal and a heavytetrel atom. Finally, Section 1.6 will provide background information regarding the tantalum precursors used to achieve tantalum-germanium multiple-bonding.
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Synthesis and characterization of complexes featuring tantalum-germanium multiple bonds, Luis Arizpe
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- 2019
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