53687-39-1Relevant academic research and scientific papers
Ammonia Borane Dehydrogenation Catalyzed by (κ4-EP3)Co(H) [EP3 = E(CH2CH2PPh2)3; E = N, P] and H2 Evolution from Their Interaction with NH Acids
Todisco, Stefano,Luconi, Lapo,Giambastiani, Giuliano,Rossin, Andrea,Peruzzini, Maurizio,Golub, Igor E.,Filippov, Oleg A.,Belkova, Natalia V.,Shubina, Elena S.
, p. 4296 - 4307 (2017/04/26)
Two Co(I) hydrides containing the tripodal polyphosphine ligand EP3, (κ4-EP3)Co(H) [E(CH2CH2PPh2)3; E = N (1), P (2)], have been exploited as ammonia borane (NH3BH3, AB) dehydrogenation catalysts in THF solution at T = 55 °C. The reaction has been analyzed experimentally through multinuclear (11B, 31P{1H}, 1H) NMR and IR spectroscopy, kinetic rate measurements, and kinetic isotope effect (KIE) determination with deuterated AB isotopologues. Both complexes are active in AB dehydrogenation, albeit with different rates and efficiency. While 1 releases 2 equiv of H2 per equivalent of AB in ca. 48 h, with concomitant borazine formation as the final spent fuel , 2 produces 1 equiv of H2 only per equivalent of AB in the same reaction time, along with long-chain poly(aminoboranes) as insoluble byproducts. A DFT modeling of the first AB dehydrogenation step has been performed, at the M06//6-311++G? level of theory. The combination of the kinetic and computational data reveals that a simultaneous B-H/N-H activation occurs in the presence of 1, after a preliminary AB coordination to the metal center. In 2, no substrate coordination takes place, and the process is better defined as a sequential BH3/NH3 insertion process on the initially formed [Co]-NH2BH3 amidoborane complex. Finally, the reaction of 1 and 2 with NH-acids [AB and Me2NHBH3 (DMAB)] has been followed via VT-FTIR spectroscopy (in the -80 to +50 °C temperature range), with the aim of gaining a deeper experimental understanding of the dihydrogen bonding interactions that are at the origin of the observed H2 evolution.
Reactivity of formaldehyde and acetaldehyde toward [N(CH2CH2PPh2)3]Ni and [N(CH2CH2PPh2)3]CoH
Bianchini, Claudio,Meli, Andrea
, p. 1537 - 1542 (2008/10/08)
The Ni(0) complex (np3)Ni [np3 = tris(2-(diphenylphosphino)ethyl)amine] reacts with formaldehyde to give the paramagnetic Ni(I) formyl complex (np3)Ni(CHO), which decomposes to the diamagnetic Ni(0) carbonyl (np3)Ni(CO). Formaldehyde reacts with the Co(I) hydride (np3)CoH or with the methyl complex (np3)Co(CH3) to give the hydrido carbonyl compound (np3)Co(CO)H. When the latter reactions are carried out in the presence of NaBPh4, the cationic carbonyl [(np3)Co(CO)]BPh4 is formed. Acetaldehyde and propionaldehyde react with (np3)CoH yielding the corresponding paramagnetic η1-acyl complexes (np3)Co(COCH3) and (np3)Co(COC2H5). The reactivity of the acetyl derivative toward nucleophiles and electrophiles is investigated. Nucleophiles displace the acetyl ligand to give the corresponding complexes (np3)Co(Nu), whereas electrophiles remove the acetyl ligand to give the [(np3)Co]+ moiety. Possible reaction mechanisms are suggested on the basis of chemical and theoretical data.
