Interaction and Activation of Carbon–Heteroatom π Bonds with a Zr/Co Heterobimetallic Complex

Abstract

Single-electron transfer from the Zr^IVCo^–I heterobimetallic complex (THF)­Zr­(MesNP^<i>i</i>Pr₂)₃Co-N₂ (<b>1</b>) to benzophenone was previously shown to result in the isobenzopinacol product [(Ph₂CO)­Zr­(MesNP^<i>i</i>Pr₂)₃Co-N₂]₂ (<b>4</b>) via coupling of two ketyl radicals. Thermolysis of <b>4</b> led to cleavage of the CO bond to generate a Zr/Co μ-oxo species featuring an unusual terminal CoCPh₂ carbene linkage (<b>3</b>). In this work monomeric ketyl radical complexes have been synthesized, and the reactivity of these compounds has been explored. The electronic preference for the formation of a ketyl radical complex or a coordination complex has been investigated computationally. Furthermore, thione substrates were allowed to react with <b>1</b>, generating new complexes that bind the thione to the Co rather than undergoing single-electron transfer (<b>12</b>,<b> 14</b>). The preference of thiones to coordinate to Co can be overridden if the Co is ligated by CO, in which case a thioketyl radical complex forms (<b>13</b>) analogous to <b>4</b>. The reaction between <b>1</b> and imines resulted in N–H bond activation, affording a μ-methyleneamido Co–H complex (<b>16</b>) that can undergo cyclometalation and loss of H₂ (<b>15</b>)