506406-67-3Relevant academic research and scientific papers
Borane B-C bond cleavage by a low-coordinate iron hydride complex and N-N bond cleavage by the hydridoborate product
Yu, Ying,Brennessel, William W.,Holland, Patrick L.
, p. 3217 - 3226 (2008/10/09)
The iron(II) hydride dimers [LRFe(μ-H)2FeL R] (LMe = 2,4-bis(2,6-diisopropylphenylimino)pent-3-yl; LtBu -2,2,6,6-tetramethyl-3,5-bis(2,6-diisopropylphenylimino)hept-4- yl) abstract hydrocarbyl groups from BR′3 (R′ = Et, Ph) to give LRFeR′ and LRFe(μ-H) 2BR′2. Mechanistic studies with R = R′ = Me are consistent with a process in which the hyride dimer opens one Fe-H bond, and subsequent B-H bond formation is concerted with dissociation of an Fe-H unit. Cleavage of boron-carbon bonds is likely to proceed at least in part from transient quaternary borate anions formed through disproportionation of HBEt3-. In a separate bond-breaking reaction, L MeFe(μ-H)2BEt2 reacts with N 2H4 to form a 1:1 adduct, which has been crystallographically characterized. Upon heating, it ejects H2 from the bridging hydrides and cleaves the N-N bond to form the diaminoborate complex LMeFe(μ-NH2)2BEt2. These novel bondbreaking reactions are facilitated by the low coordination number at the iron(II) center.
Reversible beta-hydrogen elimination of three-coordinate iron(II) alkyl complexes: Mechanistic and thermodynamic studies
Vela, Javier,Vaddadi, Sridhar,Cundari, Thomas R.,Smith, Jeremy M.,Gregory, Elizabeth A.,Lachicotte, Rene J.,Flaschenriem, Christine J.,Holland, Patrick L.
, p. 5226 - 5239 (2008/10/09)
High-spin organometallic complexes have not received extensive mechanistic study, despite their potential importance as unsaturated intermediates in catalytic transformations. We have found that, with a suitably bulky bidentate ligand, three-coordinate, high-spin alkyl complexes of iron(II) are stable. They undergo isomerization and exchange reactions of the alkyl group through β-hydride elimination and reinsertion, and the β-hydride elimination step is rate-limiting. The alkyl complexes transfer a β-hydrogen atom to C=C, C=N, and C=O double bonds and undergo deprotonation by Bronsted acids. The reversible β-hydride elimination reactions can be used to explore relative M-C bond energies. Competition experiments and density functional calculations demonstrate an enthalpic preference for alkyl isomers with iron bound to the terminal carbon of the alkyl fragment. This preference arises from steric and electronic effects. The steric preference could be overcome with a phenyl substituent, which steers iron to the benzylic position. A Hammett correlation and density functional calculations suggest that the substituent effect is attributable to resonance stabilization of partial negative charge on the alkyl ligand.
Alkyl isomerisation in three-coordinate iron(II) complexes
Vela, Javier,Smith, Jeremy M.,Lachicotte, Rene J.,Holland, Patrick L.
, p. 2886 - 2887 (2007/10/03)
The tertiary to iso-butyl isomerisation of three-coordinate iron(II) diketiminate complexes is reported and a hydride intermediate is proposed on the basis of exchange experiments.
