Doctoral Dissertations
Date of Award
5-1999
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Chemistry
Major Professor
Ziling Xue
Committee Members
Clifton Woods, James Q. Chambers, David C. Joy
Abstract
This dissertation describes research conducted on the chemistry of tantalum silyl complexes, reactions of alkylidene complexes with phenylsilanes, kinetic and mechanistic studies of the reaction of a tantalum alkylidene complex with phenylsilanes, and related organometallic chemistry. An overview and summary of the Ph.D. research project is given in Chapter 1. Chapter 2 describes the synthesis and characterization of the thermally unstable tantalum silyl alkylidene complexes (Me3ECH2)2Ta[=CHEMe3]SiPh2But (E = C, 1; Si, 2). Complexes 1 and 2 were found to decompose by elimination of HSiPh2But to unidentified products and (Me3SiCH2)4Ta2(µ-CSiMe3)2, respectively. Reaction of 1 or 2 with PMe3 leads to elimination of HSiPh2But and the formation of bis(phosphine)bis(alkylidene) complexes (Me3ECH2)Ta(PMe3)2[=CHEMe3]2 (E = C, 3; Si, 4). Chapter 3 presents the reactions of the tantalum alkylidene complexes (Me3SiCH2)3 Ta(PMe3)=CHSiMe3 (7), 4, and (Me3SiCH2)Ta(PMe3)2[=CHCMe3]2 (8) with phenylsilanes PhRSiH2 (R = Ph, Me) and (PhSiH2)2CH2 to yield novel bis(silyl)-substituted alkylidene complexes as well as the first reported 1, 1'metalla-3-silacyclobutadiene and 1, 1 '-metalla-3,5-disilacyclohexadiene complexes through the preferential reaction of the silanes with the alkylidene ligands of 4, 7, and 8. Chapter 4 describes the mechanistic investigation of the formation of the bis(silyl)-substituted alkylidene complex (Me3SiCH2)3Ta=C(SiMe3)SiPhMeH (9a) from the reaction of 7 with PhMeSiH2. Kinetic studies were found to be consistent with a dissociative mechanism in which a PMe3 molecule dissociated from the tantalum center in 7, forming an open coordination site on the metal for the reaction with PhMeSiH2. Deuterium labeling studies were consistent with a mechanism involving hydride and silyl intermediates. The final chapter discusses attempted syntheses of dianionic bis(silyl)lithium and -potassium compounds as potential ligands for the synthesis of poly- or persilyl early-transition-metal complexes. Two previously unreported bis(silyl)methane and -ethane complexes [(Me3Si)3Si]2CH2 (18) and (Me3Si)3SiCH2CH2Si(SiMe3)3 (19) were synthesized as possible ligand precursors.
Recommended Citation
Diminnie, Jonathan Bruce, "Early-transition-metal alkylidene chemistry. Synthesis of tantalum silyl alklidene complexes and reactions of tantalum alkylidene complexes with silanes. " PhD diss., University of Tennessee, 1999.
https://trace.tennessee.edu/utk_graddiss/8800