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Hafnium complexes stabilized by a macrocyclic ligand

University of British Columbia

The goal of this thesis is to investigate the chemistry of hafnium complexes of the macrocyclic ligand, PhP(CH2SiMe2NSiMe2CH2)2PPh ([P2N2]). The hafnium dichloride, [P2N2]HfCl2 (1) is used as a starting material for all other compounds synthesized. 1 is isostructural with its zirconium analogue, [P2N2]ZrCl2 , but does not exhibit identical chemistry. While reaction of [P2N2]ZrCl2 with 2 equivalents of C8K under N2 resulted in formation of a zirconium dinitrogen compound, the same is not true for the hafnium analogue. Instead, the major product of the reaction of 1 with 2 equivalents of C8K is a hafnium dimer, {[P2N2]Hf}2 (2). [P2N2]HfI2 (3) is synthesized via the reaction of 1 with excess trimethylsilyliodide. Evidence will be presented that ([P2N2]Hf)2(μ-η2:η2-N2) (4) is the major product of the reaction between 3 and 2 equivalents of C8K under dinitrogen, while {[P2N2]Hf}2 (2) and [P2N2]Hf(C7H8) (5) appear to be minor products. Reaction of 1 with 2 equivalents of MeMgCl results in the formation of [P2N2]HfMe2 (6). The zirconium analogue of 6 reacts with toluene under an atmosphere of H2 to give [P2N2]Zr(C7H8), but this is not true for 6. Instead, reaction of 6 under H2 results in the formation of a hafnium tetrahydride, {[P2N2]Hf}2(μ-H)4 (7). A metathesis reaction of one equivalent of 1 with one equivalent of Mg(C4H6)(THF)2 results in formation of [P2N2]Hf(C4H6) (8). Unlike most mononuclear [P2N2] compounds, this compound exhibits 2 inequivalent phosphorus atoms evidenced by an AB doublet pattern in the 31P{1H} NMR spectrum. [Scientific formulae used in this abstract could not be reproduced.]

Thesis/Dissertation

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2009-07-07

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http://hdl.handle.net/2429/10374

Chemistry

University of British Columbia

UBCV

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