Synthesis and small molecule chemistry of the niobaziridine-hydride functional group

Chapter 1. Synthesis and Divergent Reactivity of the Niobaziridine-Hydride Functional Group The synthesis, characterization and reactivity of the niobaziridine-hydride complex Nb(H)([eta]²-t- ]Bu(H)C=NAr)(N[Np]Ar)₂ (la-H; Np = neopentyl, Ar = 3,5-Me₂C₆H₃) is discussed. The niobaziridine-hydride functional group in complex la-H serves as a protecting group for the reactive three-coordinate d² species, Nb(N[Np]Ar)₃ (2a), via reversible C-H activation of the 3- ]H-containing N[Np]Ar ligand. At elevated temperatures, complex la-H rapidly converts to the neopentylimido complex, Nb(NNp)(Ar)(N[Np]Ar)₃ (3a), which is the product of N[Np]Ar ligand C'-N oxidative addition by putative three-coordinate 2a. Although not observed directly, the evidence for the intermediacy of 2a in N[Np]Ar ligand C-H and C-N activation processes has been obtained through isotopic labeling (H/D) studies. To further ascertain the propensity of la- H to serve as a masked form of 2a, its reactivity with small-molecule substrates was surveyed. Treatment of la-H with nitrous oxide (N₂0) or triphenylphosphine oxide (OPPh₃), readily generated the oxo Nb(V) complex, ONb(N[Np]Ar)₃, thus establishing la-H as a source of the potent two-electron reductant 2a. Complex la-H was also found to effect the two-electron reduction of a host of other inorganic substrates. However, when treated with certain unsaturated organic molecules, insertion into the Nb-H moiety of complex la-H is observed in which the niobaziridine ring is left intact. Based on synthetic studies, a coordinatively induced, C-H bond reductive elimination mechanism is proposed for reactions between la-H and small molecules.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Figueroa, Joshua S

Advisor dc:contributor.advisor

• Christopher C. Cummins.

• Chemistry.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/32479

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/32479