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New ligands for early metal activation of molecular nitrogen

University of British Columbia

The synthesis of two new proligands for early metal activation of dinitrogen is reported. The new diamidophosphine [NPN]SH ₂([NPN]SH₂ = {N-(2,4,6-Me₃C₆H₂)(3- NH-SC₄H₂)}₂PPh)proligand features a bridging thiophene ring between the phosphine and amide donors and was synthesized as a variation to other recent aryl bridged NPN ligands. The potentially dianionic linear-linked aryloxide proligand [000]H ₂([000]H₂ = 2,6-bis(3 -adamantyl-5 -t-butyl-2-hydroxybenzyl)-4-t-butylanisole) was also synthesized as a variation to other similar known compounds. The precursor to the proligand [NPN] SH₂was successfully synthesized by a high yielding N-aryl amination reaction. The second step in the synthesis produces the [NPN] SH₂ compound; however, the product has an unexpected regiochemistry. Detailed mechanistic investigations suggest a possible mechanism involving competitive lithiumhalogen and deprotonation reactions. Zr and Ti complexes of the [000] ligand could not be synthesized; however, a new “half-on” [000(H)JTaC1₄ complex was synthesized and features a pendant phenol with the ligand locked in an S-conformation. Attempts to “close” this ligand to the U conformation and form the desired [000]TaCl₃ complex have thus far failed. In contrast, Zr complexes of the [NPN]S ligand could be readily synthesized and were fully characterized. These include: [NPN]SZr(NMe₂)₂ [NPN]SZrC1₂ and [NPN] SZrI₂. Attempts to reduce [NPN] SZrC1₂ to form a dinitrogen complex have thus far failed; however, reduction of [NPN] SZrI₂ in Et₂O using KC₈ as reducing agent shows promising signs of a dinitrogen complex similar to a previously reported case in our laboratory.

Thesis/Dissertation

application/pdf

2009-03-06

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/5629

Chemistry

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/