Lewis basicity of 2-dimethylaminoborazine

Beachley, O. T.; Durkin, T. R.

doi:10.1021/ic50123a031

Cited by 9 publications

(3 citation statements)

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“…The availability of nitrogen lone pairs in these species makes them very strong bases compared to systems, such as lithium alkyls in which the basic lone pair is restricted in its availability by metal coordination, and only monolithiation of primary amines by n BuLi is typically observed 12. The increased EN bond strength and the occupation of the nitrogen lone pairs engendered by BN π‐bonding in B(NMe 2 ) 3 results in greatly reduced basicity for both kinetic and thermodynamic reasons 13. Nevertheless, reaction with moderately acidic species, such as the azoles considered here, can be observed under forcing conditions to provide the observed [(HNMe 2 )B(azolyl) 3 ] products, such as 1 .…”

Section: Resultsmentioning

confidence: 86%

Reaction of Azole Heterocycles with Tris(dimethylamino)borane, a New Method for the Construction of Tripodal Borate‐Centred Ligands

Bailey

Lorono-Gonzales

McCormack

et al. 2006

Chemistry A European J

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Reaction of 2-mercapto-1-methylimidazole (methimazole) with tris(dimethylamino)borane, B(NMe2)3, provides the tetrahedral dimethylamine adduct of tris(methimazolyl)borane, [(Me2HN)B(methimazolyl)3]. By contrast, imidazole, 2-methylimidazole, 2-chloroimidazole and benzimidazole provide the homoleptic tetra-azolyl systems H[B(azolyl)4], and the same product is obtained even when a substoichiometric quantity of the heterocyle is employed. The change in reaction outcome is correlated with the variation of basic pKa for the heterocycles. A simple acid-base reaction with elimination of HNMe2 is proposed for the reaction with the weakly basic, but more strongly acidic, methimazole. However, for the more strongly basic imidazoles, initial coordination of the heterocycle imine nitrogen to the weakly Lewis acidic boron centre in B(NMe2)3 to form the tetrahedral adduct [(azole)B(NMe2)3] is proposed. The greater availability of the NMe2 lone pairs in this species results in increased basicity and a rapid reaction with further heterocycle to provide the observed H[B(azolyl)4] products. For 2-nitroimidazole, the low basicity (and increased N-H acidity) results in the formation of [(HNMe2)B(2-nitroimidazolyl)3] on reaction with B(NMe2)3, analogous to the product formed with methimazole. Both [(HNMe2)B(methimazolyl)3] and H[B(benzimidazolyl)4] have been structurally characterised by single crystal X-ray crystallography. This chemistry has been exploited to provide a new synthesis of borate-centred tripod ligands, whereby N-methylimidazole is used to activate B(NMe2)3 to reaction with methimazole to form the new ligand [(N-methylimidazole)B(methimazolyl)3] in good yield and a complex of this ligand with Ru(II) has been structurally characterised.

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Section: Resultsmentioning

confidence: 86%

Reaction of Azole Heterocycles with Tris(dimethylamino)borane, a New Method for the Construction of Tripodal Borate‐Centred Ligands

Bailey

Lorono-Gonzales

McCormack

et al. 2006

Chemistry A European J

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“…B‐trisubstituted borazines (Figure ) are readily prepared and their chemistry has been well studied but the chemistry of the less accessible B‐monosubstituted borazines (XBaz, Figure ) has been little developed; for example, 2‐hydroxyborazine (HOBaz), the borazine analogue of phenol, has only been partially characterised in situ as part of a mixture of products formed in the photochemical oxidation of borazine . In addition, no borazines that contain P−B bonds have been reported which may be due to the anticipated high reactivity of the P−B bond …”

Section: Figurementioning

confidence: 99%

Inorganic Triphenylphosphine

et al. 2018

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Ac ompletely inorganic version of one of the most famous organophosphorus compounds,t riphenylphosphine, has been prepared. Ac omparison of the crystal structures of inorganic triphenylphosphine,P Baz 3 (where Baz = B 3 H 2 N 3 H 3 )a nd PPh 3 shows that they have superficial similarities and furthermore,t he Lewis basicities of the two compounds are remarkably similar.H owever,t heir oxygenation and hydrolysis reactions are starkly different. PBaz 3 reacts quantitatively with water to give PH 3 and with the oxidizing agent ONMe 3 to give the triply-O-inserted product P(OBaz) 3 ,a ni norganic version of triphenyl phosphite; ac orresponding transformation with PPh 3 is inconceivable. Thermodynamically,w hat drives these striking differences in the chemistry of PBaz 3 and PPh 3 is the great strength of the B À Ob ond.

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“…NICS values for benzene and borazine are À11.5 and À2.1 respectively), [23][24][25] and the dominant mechanisms by which they undergo substitution are fundamentally different:e lectrophilic aromatic substitution for benzene,a ddition-elimination for borazine. [26,27] B-trisubstituted borazines ( Figure 2) are readily prepared and their chemistry has been well studied [28][29][30][31][32][33] but the chemistry of the less accessible B-monosubstituted borazines (XBaz, Figure 2) has been little developed; [34][35][36] for example, 2-hydroxyborazine (HOBaz), the borazine analogue of phenol, has only been partially characterised in situ as part of am ixture of products formed in the photochemical oxidation of borazine. [37] In addition, no borazines that contain PÀBb onds have been reported which may be due to the anticipated high reactivity of the PÀBb ond.…”

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confidence: 99%