Guanidinates, having the general formula [(RN)2C(NR’2)]- (R = H, alkyl), are popular bidentate, anionic ligands characterized by a sp2 carbon-centered N3C- core. Because guanidinates possess a secondary amide backbone which can π-conjugate into the Y-shaped core, these ligands are considered to be excellent electron donors. In our group, we have been exploring the structural and electronic effects that ketimine (N=CR2) substituents play when substituted in place of a secondary amide. Ketimines have been shown to be strong σ and π-donors that can stabilize metals in unusually high oxidation states, yet it is unknown if similar electronic contributions are made when part of a guanidine system. We have undertaken a systematic study comparing the structural and electronic properties of a series of well-defined iron complexes [(R)C(NR’)2]FeBr (R= NiPr2, tBu, N=CtBu2; R’= 2,6-diisopropylphenyl) which differ only in their backbone substituent, the results of which will be presented. Additionally, we will discuss the unique coordination chemistry of ketimine-guanidinates, specifically their ability to stabilize low-valent iron complexes featuring ultra-short metal-metal bonds.

Synthesis, characterization, and coordination chemistry of a new guanidinate ligand class possessing ketimine backbones

249th National Meeting (2015)

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