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Fun with ferrocene : synthesis of polyiron complexes using 1,1'-diaminoferrocene based ligands

University of British Columbia

Reactions of an amidophosphine supported ditantalum tetrahydride, ([NPNSi]Ta)₂(μ-H)₄ and COx (x = 1, 2) were studied and all products were fully characterized. Selective deuteration allows for the production of two deuterated isotopomers which were used in low temperature NMR and GC-MS experiments in order to support a computationally determined mechanism. Iron and cobalt complexes of a ferrocene linked bis(phosphinoamide) were synthesized and characterized by X-ray crystallography and Mössbauer spectroscopy. The cobalt complex contains a Co–Fe bond that was absent in the all-iron complex. The Co–Fe bond was further studied using DFT calculations, which suggest that the bond is comprised of donation from the iron center to the cobalt center (Fe → Co) and back donation from the cobalt center to antibonding orbitals in the ferrocene backbone (Co → fc*). A putative nickel complex supported by the same bis(phosphinoamide) ligand underwent a reductive elimination of the amidophosphine groups forming a new P-N bond. Reactions between the aforementoned iron complex and H₂, CO₂ and other electrophiles were studied and the products of these reactions were fully characterized. The products of these reactions show that the iron phosphinoamides can cooperativley activate a variety of bonds without changing the oxidation state at iron. Upon reduction, the iron complex forms an Fe–Fe bond while remaining in a high spin state. The cleavage of the N=N double bond of azobenzene was achieved under photolytic conditions using the same iron phosphinoamide and is thought to involve formation of a putative iron imido which migrates to the phosphinoamide groups. Due to the tendency of iron phosphinoamides to activate substrates using ligand cooperativity, an alternative ligand using amidophosphine donors was syntheisized and initial coordination studies were performed.

Text

2017-07-10

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/62192

Chemistry

University of British Columbia

UBCV

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