Basicities of organometallic and other bases using the visible absorption maximum of the reference acid and its conjugate base

The shift in the visible absorption maximum of hexanitrodiphenylamine has been used as a measure of the base strengths of some organometallic and organic bases. It is not possible to obtain a quantitative measure for stronger bases as the hexanitrodiphenylamine anion is produced. The order of base strengths for the organometallic bases studied is found to be Me3SiSMe < Me3CSMe < Me3SnSMe ≈ Me3SiNMe2.

Dimethylboric anhydride: a convenient preparation and full characterization

Dimethylboric anhydride, (CH3)2BOB(CH3)2, has been prepared by limited hydrolysis of dimethylboron chloride and complete characterization has been carried out. The Lewis acid character of boron and the donor strength of oxygen have been studied using tensimetric and nuclear magnetic resonance techniques.Evidence for boron–oxygen π-bonding obtained from complex formation studies, using trimethylboron as a reference acid, is presented and discussed. The reduced acidity of the boron atoms, in comparison with trimethylboron, is discussed in terms of boron–oxygen π-bonding.