64045-95-0Relevant academic research and scientific papers
HYDROBORATION - KINETICS AND MECHANISM.
Brown,Chandrasekharan,Wang
, p. 1387 - 1414 (1983)
The kinetics of hydroboration of alkenes with several dialkylborane dimers have been studied extensively. The reaction of alkenes with the disiamylborane dimer displays second-order kinetics, first-order in the dimer and first-order in the alkene. 9-borabicyclo left bracket 3. 3. 1 right bracket nonane)//2 (9-BBN)//2, on the other hand, reacts by a prior dissociation of the dimer, followed by the reaction of the monomer with the alkene. The borinane dimer also reacts by the dissociation mechanism. By following the kinetics of the reactions of alkenes, alkynes, aldehydes and ketones, alcohols and amines with (9-BBN)//2, a spectrum of mechanistic pathways has been revealed.
Chemical Effects of Steric Strains. 24. 13C NMR Study of the Interaction of 9-Borabicyclononane with Amines of Increasing Steric Requirements
Brown, Herbert C.,Wang, Kung K.
, p. 1748 - 1753 (1980)
The 13C NMR spectra of the interaction of 9-borabicyclononane (9-BBN) with two series of amines, involving regularly increasing steric requirements, were used to study the role of steric strains as a factor in the stability of addition compounds formed and their exchange with the amine.A set of pyridine bases, including pyridine and 2-methyl-, 2-ethyl-, 2-isopropyl-, and 2-tert-butylpyridines, and a set of aliphatic amines, including n-propylamine, isopropylamine, diethylamine, diisopropylamine, and triethylamine, with increasing steric requirements were selected for examination.Quinuclidine was also selected, as a base of relatively low steric requirements, for comparison with triethylamine, a base with very large steric requirements.The results reveal four types of behavior: formation of stable complexes with no observable exchange with excess amine; formation of stable complexes with rapid exchange of amine; formation of partially dissociated complexes with rapid exchange; and no detectable interaction of 9-BBN and amines of large steric requirements.In general, there is a regular progression along these four types of behavior with increasing steric requirements in both series of amines.Thus, triethylamine fails to show any interaction with 9-BBN, whereas quinuclidine forms a stable adduct which does not exchange with excess amine. 13C NMR provides a valuable tool for exploring the role of such steric effects in the formation and stability of molecular addition compounds.
Europium(II) and Ytterbium(II) Cyclic Organohydroborates: An Europium(II) Complex with an Agostic Interaction
Chen, Xuenian,Lim, Soyoung,Plecnik, Christine E.,Liu, Shengming,Du, Bin,Meyers, Edward A.,Shore, Sheldon G.
, p. 692 - 698 (2008/10/09)
Lanthanide bis((cyclooctane-1,5-diyl)dihydroborate) complexes (THF) 4Ln{(μ-H)2BC8H14}2 (Ln = Eu, 1; Yb, 2) were synthesized by a metathesis reaction between (THF) xLnCl2 and K[H2BC8H14] in THF in a 1:2 molar ratio. Attempts to prepare the monosubstituted lanthanide cyclic organohydroborates (THF)xLnCl{(μ-H)2BC 8H14} were unsuccessful. On the basis of the molecular structure and IR spectrum of 1, there is an agostic interaction between Eu(II) and one of the α-C-H hydrogens from the {(μ-H)2BC 8H14} unit. No such interaction was observed for 2. The coordinated THF in 1 and 2 can be removed under dynamic vacuum, but the solvent ligands remain bound to Yb when 2 is directly dissolved in Et2O or toluene. In strong Lewis basic solvents, such as pyridine or CH3CN, attack of the Yb-H-B bridge bonds results. Decomposition of 2 to the 9-BBN dimer in CD2Cl2 was observed by 11B and 1H NMR spectroscopies. Compound 2 was reacted with 2 equiv of the hydride ion abstracting reagent B(C6F5)3 to afford the solvent-separated ion pair [Yb(THF)6][HB(C 6F5)3]2 (3). Complexes 1, 2, and 3 were characterized by single-crystal X-ray diffraction analysis. Crystal data: 1 is orthorhombic, Pna21, a = 21.975(1) A, b = 9.310(1) A, c = 16.816(1) A, Z = 4; 2 is triclinic, P1, a = 9.862(1) A, b = 10.227(1) A, c = 10.476(1) A, α = 69.87(1)°, β = 76.63(1)°, γ = 66.12(1)°, γ = 1; 3.Et2O is triclinic, P1, a = 13.708(1) A, b =14.946(1) A, c = 17.177(1) A, α = 81.01(1)°, β = 88.32(1)°, γ = 88.54(1)°, Z = 2.
