Spectroscopic studies for tetraphenylporphyrincobalt(II) complexes of carbon monoxide, nitrogen oxide, molecular oxygen, methylisonitrile, and trimethyl phosphite, and a bonding model for complexes of carbon monoxide, nitrogen oxide, and molecular oxygen with cobalt(II) and iron(II) porphrins

Abstract

boring ethyl groups would very much increase if Ni(OEPMe2) were dehydrogenated to , -dimethyloctaethylporphinatonickel(II), Ni(ODM). Therefore, Ni(OEPMe2) is air-stable. Ni(ODM) may be obtained, however, by metal insertion into the parent porphine.19 In Ni(ODM), the methyl • • • methylene carbon contacts are expected to be substantially smaller than the ^3.9A contacts found for Ni(OEPMe2). Indeed, if Ni-(ODM) has the same highly ruffled core of Ni(OEP),31b the nonbonded contacts can be calculated to be an unreasonably tight 2.8 Á. Hence, Ni(ODM) must represent a metalloporphyrin with a severely distorted core.

Factors contributing to one-electron metalloradical activation of ethene and carbon monoxide illustrated by reactions of Co(II), Rh(II), and Ir(II) porphyrins

“…Cobalt(II), rhodium(II), and iridium(II) porphyrins as metal-centered radicals Cobalt(II) porphyrins are invariably monomeric (S = 1/2) species [26,27], but rhodium(II) and iridium(II) derivatives with lower steric requirement porphyrins, such as octaethylporphyrin (OEP) and tetraphenylporphyrin (TPP), occur as metal-metal bonded dimers [28,29]. Inter-porphyrin repulsions not only prohibit the cobalt(II) centers from reaching an effective Co II -Co II bonding distance, but also reduce the Rh II -Rh II and Ir II -Ir II bond dissociation enthalpies such that the M-M bonded dimers are facile sources of metal-centered radicals ((por)Rh IIÅ , (por)Ir IIÅ ).…”

Carbene Radicals in Cobalt(II)–Porphyrin‐Catalysed Carbene Carbonylation Reactions; A Catalytic Approach to Ketenes

“…[5c, 6] Given that carbon monoxide has a weak affinity for the cobalt(II) center, [14] it is unlikely for carbon monoxide to bind to the catalyst and thus influence the carbonylation of diazo compounds under the applied catalytic reaction conditions. The more nucleophilic character of C compared to Fischertype carbenes further reduces its reactivity towards nucleophiles, which is likely an important feature in preventing unwanted side-reactions.…”

Role of Iron (Fe) in Body

“…Any adequate theoretical treatment must also explain how iron-porphyrin systems can bind not only O 2 but also CO, NO,alkyl isocyanides,and alkyl-nitroso moieties. A simple qualitative model presented by Wayland and coworkers [20,21] conveniently summarizes ligand-binding geometries of cobalt and iron porphyrins. Although a reasonable quantative theoretical consensus exists for 1:1 cobalt-dioxygen species, the same cannot be said yet for irondioxygen systems.…”