We report a mechanistic study of C(sp)-H bond activation mediated by nickel. Cyclometalated Ni(II) ureate [(PEt)Ni(κ- C,N,N-(CH)N(Cy)(CO)N((N)-quinolin-8-yl))] was synthesized and isolated from the urea precursor, (Me)(Cy)N(CO)N(H)(quinolin-8-yl), via C(sp)-H activation. We investigated the effects of solvents and base additives on the rate of C-H activation. Kinetic isotope effect experiments showed that C-H activation is rate determining. Through deuterium labeling and protonation studies, we also showed that C-H activation can be reversible. We extended this reaction to a range of ureas with primary and secondary C(sp)-H bonds, which activate readily to form analogous nickelated products. Finally, we showed that carboxylate additives assist with both ligand dissociation and initial N-H bond activation, consistent with a concerted metalation-deprotonation mechanism.

A series of technetium complexes with (η5-cyclopentadienyl)­tris­(dimethyl phosphito-P)­cobaltate­(III), also known as the “Kläui ligand” {LOMe}−, has been prepared. The products span seven different oxidation states (+1 to +7) of the radioactive transition metal and comprise nitrosyl, halide, oxido and nitrido complexes. All members of this series ([TcI(NO)­Cl­(PPh3)­(LOMe)], [TcII(NO)­Cl2(LOMe)], [TcIIICl2(PPh3)­(LOMe)], [TcIVCl3(LOMe)], [TcVOCl2(LOMe)], [TcVNCl­(PPh3)­(LOMe)], [TcVINCl2(LOMe)], and [TcVIIO3(LOMe)] are air- and water-stable compounds, which recommends this class of technetium complexes as potential candidates for nuclear medical imaging procedures.

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