66217-56-9Relevant articles and documents
Cobalt-bis(imino)pyridine complexes as catalysts for hydroalumination-isomerisation of internal olefins
Weliange, Nandita M.,McGuinness, David S.,Gardiner, Michael G.,Patel, Jim
, p. 10842 - 10849 (2016)
The insertion of α- and internal octenes (hydroalumination) and chain walking isomerisation at di-n-octylaluminium hydride [Al(Oct)2H], catalysed by bis(imino)pyridine-Co complexes has been investigated by NMR spectroscopy. The Co-based catalysts promote efficient hydroalumination of 1-octene. Internal olefins are partially hydroaluminated, with isomerisation to the primary alkyls, but the catalyst responsible appears to deactivate rapidly. The reaction between the Co precatalysts and [Al(Oct)2H] generates a Co-hydride species, likely to be a hydride bridged dinuclear Co and Al complex. This species is reactive towards α-olefins but inert towards internal olefins. In contrast to hydroalumination, the catalysts promote efficient hydroboration, where insertion and isomerisation of internal octenes goes to completion. The differences between the systems may be partially ascribed to formation of an active mononuclear Co catalyst in the borane system versus a less active Co/Al dinuclear complex in hydroalumination.
Alkene Isomerization-Hydroboration Catalyzed by First-Row Transition-Metal (Mn, Fe, Co, and Ni) N-Phosphinoamidinate Complexes: Origin of Reactivity and Selectivity
Macaulay, Casper M.,Gustafson, Samantha J.,Fuller, Jack T.,Kwon, Doo-Hyun,Ogawa, Takahiko,Ferguson, Michael J.,McDonald, Robert,Lumsden, Michael D.,Bischof, Steven M.,Sydora, Orson L.,Ess, Daniel H.,Stradiotto, Mark,Turculet, Laura
, p. 9907 - 9925 (2018/10/15)
We describe the results of our combined experimental and computational investigation of structurally analogous (N-phosphinoamidinate)metal(N(SiMe3)2) precatalysts ((PN)M; M = Mn2+, Fe2+, Co2+, and Ni2+ d5-d8) in the isomerization-hydroboration of 1-octene, cis-4-octene, or trans-4-octene (1a-c) with HBPin. As part of this investigation, the synthesis and crystallographic characterization of diamagnetic (PN)Ni, ((PN)NiH)2, (PN)NiH(L) (L = pyridine or DMAP), and (PN)Ni(NHdipp) (dipp = 2,6-iPr2C6H3) are reported. Divergent catalytic reactivity and selectivity was noted for members of the (PN)M series; (PN)Mn and (PN)Ni afforded poor hydroboration yields, whereas the use of (PN)Fe or (PN)Co afforded high conversion and selectivity for the terminal borylation product, (n-octyl)BPin (2a). DFT calculations involving (PN)M as well as stoichiometric reactivity studies featuring (PN)Ni confirmed that (PN)MH intermediates generated upon reaction of (PN)M with HBPin represent viable catalytic species whereby formation of putative (PN)Ni(H2BPin) is reversible. Conversely, poor catalytic performance was noted for ((PN)NiH)2 and (PN)NiH(L) (L = pyridine or DMAP). Using DFT calculations, the relative reactivity of (PN)M precatalysts was found to be a function of their spin-state energy gaps. For reaction of (PN)MnH with trans-4-octene (1c) there is no viable spin crossover mechanism and migratory insertion is slow, resulting in poor reaction yields. In contrast, (PN)FeH can access a lower barrier through spin crossover, whereas (PN)CoH has a very low migratory insertion barrier from its low spin state. While (PN)NiH has a reasonable migratory insertion barrier, it is plausible that off-catalytic cycle intermediates are responsible for the diminished reaction rate and product yields that are observed experimentally. On the basis of the computed isomerization and borylation energy landscapes, a Curtin-Hammett-type scenario with fast isomerization through β-hydride elimination and migratory insertion steps is proposed, giving rise to a catalytic equilibrium of isomeric (PN)M(octyl) resting states, followed by slow product-forming borylation. The significantly lower barriers calculated for borylation of terminal (PN)M(n-octyl) species versus isomeric internal (PN)M(CHR2) intermediates provides a rationale for the experimentally observed terminal isomerization-hydroboration selectivity.
Rhodium-catalyzed dehydrogenative borylation of aliphatic terminal alkenes with pinacolborane
Morimoto, Masao,Miura, Tomoya,Murakami, Masahiro
supporting information, p. 12659 - 12663 (2015/10/28)
Aliphatic terminal alkenes react with pinacolborane at ambient temperature to afford dehydrogenative borylation compounds as the major product when iPr-Foxap is used as the ligand with cationic rhodium(I) in the presence of norbornene, which acts as the s
