Abstract Catalysis ofO‐atom transfer (OAT) reactions is a characteristic of both natural (enzymatic) and synthetic molybdenum‐oxo and ‐peroxo complexes. These reactions can employ a variety of terminal oxidants, e. g. DMSO,N‐oxides, and peroxides, etc., but rarely molecular oxygen. Here we demonstrate the ability of a set of Schiff‐base‐MoO2complexes (cy‐salen)MoO2(cy‐salen=N,N’‐cyclohexyl‐1,2‐bis‐salicylimine) to catalyze the aerobic oxidation of PPh3. We also report the results of a DFT computational investigation of the catalytic pathway, including the identification of energetically accessible intermediates and transition states, for the aerobic oxidation of PMe3. Starting from the dioxo species, (cy‐salen)Mo(VI)O2(1), key reaction steps include: 1) associative addition of PMe3to an oxo‐O to give LMo(IV)(O)(OPMe3) (2); 2) OPMe3dissociation from2to produce mono‐oxo complex (cy‐salen)Mo(IV)O (3); 3) stepwise O2association with3via superoxo species (cy‐salen)Mo(V)(O)(η1‐O2) (4) to form the oxo‐peroxo intermediate (cy‐salen)Mo(VI)(O)(η2‐O2) (5); 4) theO‐transfer reaction of PMe3with oxo‐peroxo species5at the oxo‐group, rather than the peroxo unit leading, after OPMe3dissociation, to a monoperoxo species, (cy‐salen)Mo(IV)(η2‐O2) (7); and 5) regeneration of the dioxo complex (cy‐salen)Mo(VI)O2(1) from the monoperoxo triplet37or singlet17by a concerted, asynchronous electronic isomerization. An alternative pathway for recycling of the oxo‐peroxo species5to the dioxo‐Mo1via a bimetallic peroxo complex LMo(O)‐O−O‐Mo(O)L8is determined to be energetically viable, but is unlikely to be competitive with the primary pathway for aerobic phosphine oxidation catalyzed by1.
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A new species of Iochroma Benth. (Solanaceae) from the eastern Andes of Colombia
Iochroma orozcoaeA.Orejuela & S.D.Sm.,sp. nov.(Solanaceae) is described from the Andean forests of Cundinamarca in the eastern cordillera of Colombia.Iochroma orozcoaewas first collected by the eminent Spanish priest and botanist José Celestino Mutis in the late part of the 18thcentury, but the specimens have lain unrecognised in herbaria for over 200 years. The species shares many features with its closest relative,Iochroma baumiiS.D.Sm. & S.Leiva, but it differs from it in having small flowers with five corolla lobes and few inflorescences per branch, located near the shoot apex with 1 to 4 (–8) flowers, fruits that are greenish-yellow when ripe and its restricted geographic distribution. A description ofI. orozcoaeis provided, along with a detailed illustration, photographs of live plants, a comparison with closely-related species and a key to all Colombian species ofIochromaBenth. In closing, we emphasise the value of historical collections for the knowledge of biodiversity.
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- Award ID(s):
- 1902797
- PAR ID:
- 10495934
- Publisher / Repository:
- Pensoft
- Date Published:
- Journal Name:
- PhytoKeys
- Volume:
- 232
- ISSN:
- 1314-2011
- Page Range / eLocation ID:
- 133 to 144
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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