Publication Type Journal Article
Title Cobalt(I) Complexes of 5-Aryl-2-iminopyrrolyl Ligands: Synthesis, Spin Isomerism, and Application in Catalytic Hydroboration
Authors Tiago F. C. Cruz Luis F. Veiros Pedro T. Gomes
Groups IOARC
Journal INORGANIC CHEMISTRY
Year 2018
Month December
Volume 57
Number 23
Pages 14671-14685
Abstract This work reports the first successful isolation and full characterization of cobalt(I) complexes of 5-aryl-2-iminopyrrolyl ligands. In one approach, when [Co\kappa N-2,N -5-(2,4,6-R-3-C6H2)-NC4H2-2-C(H)= N(2,6-Pr-i(2)-C6H3)\(Py)Cl] (R = Pr-i, 1a; R = Ph, 1b) were reacted with K(HBEt3) or Na(Hg) in toluene, the Co(I) arene complexes [Co\kappa N-2,N 5-(2,4,6-Pr-i(3)-C6H2)-NC4H2-2-C(H)=N(2,6-Pr-i(2)-C6H3)\(eta(6)-C 6H5CH3)] (2a) and [Co\kappa N-2,N -5-[2 -(kappa:eta(6)-C6H5)-C6H2-4 ,6 -Ph-2]-NC4H2-(2)-C(H)= N(2,6-Pr-i(2)-C6H3)\] (2b) were formed. The reaction of complex la with KC8 in Et2O yielded the [Co\kappa N-2,N -5-(2,4,6-Pr-i(3)-C6H2)-NC4H2-2-C(H)= N(2,6-Pr-i(2)-C6H3)\](2) (3). On another approach, the metathesis of potassium 5-(2,4,6-triisopropylpheny1)-2-(N-2,6-diisopropylphenylformimino)pyrroly l (KLa) with CoCl(PMe3)(3) yielded the bis(trimethylphosphine) complex [Co\kappa N-2,N -5-(2,4,6-Pr-i(3)-C6H2)-NC4H2-2-C(H)=N(2,6-Pr-i(2)-C6H3)\(PMe3)(2 )] (4) in a good yield. Complexes 2a, 3, and 4 are paramagnetic, high-spin species, while 2b is a diamagnetic complex. Compound 2b exhibited a spin isomerism behavior (S = 0 <-> S = 1) as determined by variable-temperature NMR experiments (Delta H degrees = 7.7 kcal mol(-1)), being also supported by computational studies (Delta E = 4.2 kcal mol(-1)). All complexes were tested in the hydroboration of styrene with pinacolborane (HBPin), with complex 4 exclusively yielding the respective anti-Markovnikov addition product. Additionally, all complexes catalyzed the fast and quantitative hydroboration of benzaldehyde with HBPin.
DOI http://dx.doi.org/10.1021/acs.inorgchem.8b02392
ISBN
Publisher
Book Title
ISSN 0020-1669
EISSN 1520-510X
Conference Name
Bibtex ID ISI:000452344400027
Observations
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