CaltechTHESIS
  A Caltech Library Service

Oxo, imido, and borollide complexes of tantalum and zirconium

Citation

Quan, Roger Weihong (1994) Oxo, imido, and borollide complexes of tantalum and zirconium. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechTHESIS:07052012-161238837

Abstract

The preparation of reactive oxo, imido, and borollide complexes on tantalum and zirconium will be described. Metathesis of Cp*2Ta(=O)Cl with AgPF6 afforded [Cp*2TaF2HPF6], which presumably formed from P-F activation of PF6-. When AgS03CF3 was used, [Cp*2Ta(=O)][S03CF3] was isolated; however, it was unreactive toward styrene, methane, or benzene. Exposure to water resulted in the 1,2-addition product, [Cp*2Ta(OH)2][S03CF3]. Finally, treating Cp*2Ta(=O)H with [Ph3C][B(C6F5)4] afforded [Cp*2Ta(=O)][B(C6F5)4]. Even with this non-coordinating counterion, the complex was found to be surprisingly unreactive. To prepare an imido complex, treating Cp*TaCl4 with four equivalents of lithium anilide affords Cp*Ta(=NPh)(NHPh)2. This complex reacts readily with substituted anilines to generate Cp*Ta(=NPh')(NHPh')2 and with alcohols such as pinacol to afford Cp*Ta(OCMe2CMe2O)2, products whereby both the imido and amido groups are exchanged. Exposing Cp*Ta(=NPh)(NHPh)2 to C02 resulted in the isolation of Cp*Ta(OCONPh)(η4-OCONHPh)2 with both the formal [2+2] addition of C02 across the imido group and insertion of C02 into the amido group. Finally, bis-imido complexes were prepared by treating Cp*Ta(=NPh)(NHPh)2 to one equivalent of HCl to yield Cp*Ta(=NPh)2 or by treating Cp*TaCl4 with four equivalents of lithium 2,6-diisopropylanilide to yield Cp*Ta(=NPh")2. The borollide ligand, (C4H4BNiPr2)2-, ligand is introduced by treating Cp*ZrCl3 with one equivalent of Li2(C4H4BNiPr2)•THF to generate Cp*(C4H4BNiPr2)ZrCl•LiCl. This complex contains a η5- coordinated borollide ligand, as shown by an X-ray crystal structure analysis. Alkylation and arylation with trimethylsilylmethyllithium, benzylpotassium or phenyllithium yielded Cp*(C4H4BNiPr2)ZrR complexes. These catalysts polymerizes ethylene, but only oligomerizes α-olefins. In addition, Cp*(C4H4BNiPr2)ZrCl•LiCl has been found to exhibit the formal heterolytic cleavage of HCl and CH3I, affording Cp*(C4H4BNHiPr2)ZrCl2 and Cp*(C4H4BNiPr2)ZrCl(I), respectively. Finally, treatment of Cp*(C4H4BNiPr2)ZrCl•LiCl with LiNHtBu generated the zwitterionic complex, Cp*(C4H4BNHiPr2)Zr=NtBu.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Chemistry
Degree Grantor:California Institute of Technology
Division:Chemistry and Chemical Engineering
Major Option:Chemistry
Thesis Availability:Restricted to Caltech community only
Research Advisor(s):
  • Bercaw, John E.
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 November 1993
Record Number:CaltechTHESIS:07052012-161238837
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:07052012-161238837
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:7169
Collection:CaltechTHESIS
Deposited By: John Wade
Deposited On:05 Jul 2012 23:26
Last Modified:14 Jan 2013 22:45

Thesis Files

[img] PDF - Final Version
Restricted to Caltech community only
See Usage Policy.

20Mb

Repository Staff Only: item control page