Lewis Acidity in Haloalkyl Orthoborate and Metaborate Esters

Abstract The Lewis acidities of a series of haloalkyl orthoborate and metaborate esters have been determined by Gutmann's 31P NMR method. The introduction of halogens into the alkyl group of the borate generally increases the Lewis acidity at boron. Detailed analysis of data indicate that systematic variations correlate with Taft's electronic σ* substituent parameters. Keywords:: Acceptor Number (AN)borate esterhaloalkylsLewis acidTaft σ* parameter