Nguyen Andy I, Hadt Ryan G, Solomon Edward I, Tilley T Don
Department of Chemistry, University of California at Berkeley, Berkeley, California 94720-1460.
Department of Chemistry, Stanford University, Stanford, California 94305.
Chem Sci. 2014 Jul 1;5(7):2874-2878. doi: 10.1039/C4SC00108G.
A dianionic, square planar cobalt(II) complex reacts with O in the presence of acetonitrile to give a cyanomethylcobalt(III) complex formed by C-H bond cleavage. Interestingly, PhIO and -tolylazide react similarly to give the same cyanomethylcobalt(III) complex. Competition studies with various hydrocarbon substrates indicate that the rate of C-H bond cleavage greatly depends on the Ka of the C-H bond, rather than on the C-H bond dissociation energy. Kinetic isotope experiments reveal a moderate KIE value of 3.5 using either O or PhIO. The possible involvement of a cobalt(IV) oxo species in this chemistry is discussed.
一种二价阴离子平面正方形钴（II）配合物在乙腈存在下与氧气反应，通过C-H键断裂生成一种氰甲基钴（III）配合物。有趣的是，次碘酸苯酯（PhIO）和对甲苯叠氮化物的反应类似，生成相同的氰甲基钴（III）配合物。对各种烃类底物的竞争研究表明，C-H键断裂的速率很大程度上取决于C-H键的Ka，而不是C-H键的解离能。动力学同位素实验表明，使用氧气或次碘酸苯酯（PhIO）时，动力学同位素效应（KIE）值适中，为3.5。本文讨论了钴（IV）氧物种在该化学反应中可能的参与情况。
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