1394797-23-9Relevant articles and documents
Reactivity of a T-shaped cobalt(i) pincer-complex
Blasius, Clemens K.,Gade, Lutz H.,Matveeva, Regina,Wadepohl, Hubert
, p. 6802 - 6810 (2021)
The reactivity of a paramagnetic T-shaped cobalt(i) complex, [(iPrboxmi)Co], stabilised by a monoanionic bis(oxazolinylmethylidene)-isoindolate (boxmi) NNN pincer ligand is described. The exposure to carbon monoxide as an additional neutral ligand resulted in the square-planar species [(iPrboxmi)Co(CO)], accompanied by a change in the electronic spin state from S = 1 to S = 0. In contrast, upon treatment with trimethylphosphine the formation of the distorted tetrahedral complex [(iPrboxmi)Co(PMe3)] was observed (S = 1). Reacting [(iPrboxmi)Co] with iodine (I2), organic peroxides (tBu2O2, (SiMe3)2O2) and diphenyldisulphide (Ph2S2) yielded the tetracoordinated complexes [(iPrboxmi)CoI], [(iPrboxmi)Co(OtBu)], [(iPrboxmi)Co(OSiMe3)] and [(iPrboxmi)Co(SPh)], respectively, demonstrating the capability of the boxmi-supported cobalt(i) complex to homolytically cleave bonds and thus its distinct one-electron reactivity. Furthermore, a square-planar cobalt(ii) alkynyl complex [(iPrboxmi)Co(CCArF)] was identified as the main product in the reaction between [(iPrboxmi)Co] and a terminal alkyne, 4-fluoro-1-ethynylbenzene. Putting such species in the context of the previously investigated hydroboration catalysis, its stoichiometric reaction with pinacolborane revealed its potential conversion into a cobalt(ii) hydride complex, thus confirming its original attribution as off-cycle species.
Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration
Zhang, Guoqi,Wu, Jing,Zeng, Haisu,Neary, Michelle C.,Devany, Matthew,Zheng, Shengping,Dub, Pavel A.
, p. 874 - 884 (2019/01/14)
This paper reports the first example of dearomatization of ubiquitous terpyridine (tpy) ligands via 2′/6′-, 3′/5′-, or 4′-selective alkylation of the central pyridine ring. The reaction is mediated by the most abundant metal in the Earth's crust, aluminum (Al), and depending on the conditions employed, exhibits ionic or radical character as suggested by experimental and computational analysis. In the latter case, intermediate formation of an AlIII complex supported by π-radical monoanionic ligand (tpy?)1- is apparent. The 3′/5′-alkylation leads to unprecedented zwitterionic Meisenheimer AlIII complexes, which were identified as efficient precatalysts for the selective hydroboration of C=O and C-C functionalities. Turnover numbers (TONs) up to ～1000 place the corresponding complexes in the category of the most efficient Al catalysts reported to date for the title reaction. The acquired data suggest that aluminum monohydrides, or more likely dihydrides, could be relevant catalytic species. Alternatively, one can also imagine a mechanistic scenario in which the dearomatized "chemically noninnocent" ligand acts as hydride donor, and a detailed investigation of this is warranted in the future.
Stable, Yet Highly Reactive Nonclassical Iron(II) Polyhydride Pincer Complexes: Z-Selective Dimerization and Hydroboration of Terminal Alkynes
Gorgas, Nikolaus,Alves, Luis G.,St?ger, Berthold,Martins, Ana M.,Veiros, Luis F.,Kirchner, Karl
supporting information, p. 8130 - 8133 (2017/06/27)
The synthesis, characterization, and catalytic activity of nonclassical iron(II) polyhydride complexes containing tridentate PNP pincer-type ligands is described. These compounds of the general formula [Fe(PNP)(H)2(η2-H2)]
