Borane dative bond with

Bond order, SHMO, 91-92 Bond strength, see Bond dissociation energy 9-Borabicyclo[3.3.1]nonane (9-BBN), 12 Borane (BH3) dative bond with NH3, 262 Boranes, 84... 

The formation of a strong intramolecular dative P—B bond in the hydro-borylation reaction of diallylphenylphosphine with triethylaminophenyl-borane results in a bicyclic product, l-borata-5-phosphoniabi-cyclo[3,3,0]octane (204) [Eq. (145)] (64JA5045). The presence of the dative bond in this compound is indicated by an NMR study and by its stability to hydrolysis and oxidation. 

The reaction between a Lewis acid R3M and a Lewis base ER3 is of fundamental interest in main group chemistry. Synthetic and computational chemists have investigated the influence of both the Lewis acid and the base on the solid state structure and the thermodynamic stability of the corresponding adduct, that is usually expressed in terms of the dissociation enthalpy De. This led to a sophisticated understanding of the nature of dative bonding interactions. In particular, reactions of boranes, alanes and gallanes MR3 with amines and phosphines ER3, typically leading to adducts of the type R3M <— ER3, have been studied.10... 

Reactions related to these are the many which occur in the gas phase between boranes and molecules with insufficient dative bonding power to permit formation of a definite complex even at low temperature for example,... 

The mechanism of action of FLPs is the subject of considerable interest. Initial speculation noted the earlier computations for BH3-H2 adducts as well as the matrix isolation studies that demonstrated the interaction of phosphine with H2. More recent DFT studies by Papal and coworkers [32] infer a mechanism that proceeds via an encounter complex (Figure 11.1) in which the phosphine and borane approach but do not form a dative bond. Rather, the complex is stabilized by H-F interactions, yielding a pocket that is proposed to react with H2. An analogous mechanism has been proposed for the QF linked systems R2P(QF4> B(QF5)2 [33],... 

Formation of a dimerized species is common in tricoordinated boranes lacking steric hindrance. Their presence leads to a shift towards lower resonance frequencies and the possibility of more convoluted spectra by virtue of additional coupling interactions. Dative interactions with boron, where the two electrons forming the bond originate from another moleeule (the solvent or a basic ligand), also lead to higher field shifts. 

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