Borane Derivatives (borane + derivative)

Distribution by Scientific Domains


Selected Abstracts


Innentitelbild: Reaction of Singlet Dioxygen with Phosphine,Borane Derivatives: From Transient Phosphine Peroxides to Crystalline Peroxoboronates (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 35 2010
35/2010)
Ambiphile Phosphan-Boronate spalten Singulett-Disauerstoff unter milden Bedingungen. Wie D. Bourissou et,al. in ihrer Zuschrift auf S.,6322,ff. erläutern, lagern sich dabei die zunächst gebildeten Phosphanperoxide spontan in stabile kristalline Peroxoboronate um. Bildgestaltung Christian Pradel. [source]


Reaction of Singlet Dioxygen with Phosphine,Borane Derivatives: From Transient Phosphine Peroxides to Crystalline Peroxoboronates,

ANGEWANDTE CHEMIE, Issue 35 2010
Susana Porcel Dr.
Singulett-Disauerstoff wird durch Phosphan-Boronate unter milden Bedingungen einfach gespalten. Die zunächst gebildeten Phosphanperoxide lagern sich spontan unter B,O-Wanderung zu Peroxoboronaten um. Diese wurden strukturell charakterisiert, und ihre Eignung für Sauerstofftransferreaktionen wurde nachgewiesen. [source]


Borane chain transfer reaction in olefin polymerization using trialkylboranes as chain transfer agents

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2010
Wentian Lin
Abstract This article discusses a new borane chain transfer reaction in olefin polymerization that uses trialkylboranes as a chain transfer agent and thus can be realized in conventional single site polymerization processes under mild conditions. Commercially available triethylborane (TEB) and synthesized methyl-B-9-borabicyclononane (Me-B-9-BBN) were engaged in metallocene/MAO [depleted of trimethylaluminum (TMA)]-catalyzed ethylene (Cp2ZrCl2 and rac -Me2Si(2-Me-4-Ph)2ZrCl2 as a catalyst) and styrene (Cp*Ti(OMe)3 as catalyst) polymerizations. The two trialkylboranes were found,in most cases,able to initiate an effective chain transfer reaction, which resulted in hydroxyl (OH)-terminated PE and s -PS polymers after an oxidative workup process, suggesting the formation of the B-polymer bond at the polymer chain end. However, chain transfer efficiencies were influenced substantially by the steric hindrances of both the substituent on the trialkylborane and that on the catalyst ligand. TEB was more effective than TMA in ethylene polymerization with Cp2ZrCl2/MAO, whereas it became less effective when the catalyst changed to rac -Me2Si(2-Me-4-Ph)2ZrCl2. Both TEB and Me-B-9-BBN caused an efficient chain transfer in the Cp2ZrCl2/MAO-catalyzed ethylene polymerization; nevertheless, Me-B-9-BBN failed in vain with rac -Me2Si(2-Me-4-Ph)2ZrCl2/MAO. In the case of styrene polymerization with Cp*Ti(OMe)3/MAO, thanks to the large steric openness of the catalyst, TEB exhibited a high efficiency of chain transfer. Overall, trialkylboranes as chain transfer agents perform as well as BH-bearing borane derivatives, and are additionally advantaged by a much milder reaction condition, which further boosts their applicability in the preparation of borane-terminated polyolefins. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3534,3541, 2010 [source]


The Ever-Surprising Chemistry of Boron: Enhanced Acidity of Phosphine,Boranes

CHEMISTRY - A EUROPEAN JOURNAL, Issue 18 2009
Marcela Hurtado Dr.
Abstract The acidity-enhancing effect of BH3 in gas-phase phosphine,boranes compared to the corresponding free phosphines is enormous, between 13 and 18 orders of magnitude in terms of ionization constants. Thus, the enhancement of the acidity of protic acids by Lewis acids usually observed in solution is also observed in the gas phase. For example, the gas-phase acidities (GA) of MePH2 and MePH2,BH3 differ by about 118,kJ,mol,1 (see picture). The gas-phase acidity of a series of phosphines and their corresponding phosphine,borane derivatives was measured by FT-ICR techniques. BH3 attachment leads to a substantial increase of the intrinsic acidity of the system (from 80 to 110,kJ,mol,1). This acidity-enhancing effect of BH3 is enormous, between 13 and 18 orders of magnitude in terms of ionization constants. This indicates that the enhancement of the acidity of protic acids by Lewis acids usually observed in solution also occurs in the gas phase. High-level DFT calculations reveal that this acidity enhancement is essentially due to stronger stabilization of the anion with respect to the neutral species on BH3 association, due to a stronger electron donor ability of P in the anion and better dispersion of the negative charge in the system when the BH3 group is present. Our study also shows that deprotonation of ClCH2PH2 and ClCH2PH2,BH3 is followed by chloride departure. For the latter compound deprotonation at the BH3 group is found to be more favorable than PH2 deprotonation, and the subsequent loss of Cl, is kinetically favored with respect to loss of Cl, in a typical SN2 process. Hence, ClCH2PH2,BH3 is the only phosphine,borane adduct included in this study which behaves as a boron acid rather than as a phosphorus acid. [source]