A variety of electrostatically enhanced 3-and 4pyridylborate salt catalysts are reported and show significant improvement over an activated noncharged neutral control compound. Their nucleophilicity in a stoichiometric S N 2 reaction and catalytic performance in a urethane synthesis are evaluated along with three methods for rapidly evaluating the basicity of these species. That is, qualitative titrations in CH 2 Cl 2 and CHCl 3 were carried out, two separate solution-state IR studies in CCl 4 and CDCl 3 are reported, and the proton affinities of the anionic components of the salts were computed. Charge differences between the anion and its protonated zwitterionic conjugate acid are evaluated along with the highest occupied molecular orbitals of the anions in relationship to some of the surprising reactivity findings that were observed in the two kinetic studies.

The tetramer of bis(4-di-n-butylaminophenyl)(pyridin-3-yl)borane [systematic name: 2λ4,4λ4,6λ4,8λ4-tetrabora-1,3,5,7(1,3)-tetrapyridinacyclooctaphane-11,31,51,71-tetrakis(ylium)], C132H192B4N12, was synthesized unexpectedly and crystallized. Its structure contains an unusual 16-membered ring core made up of four (pyridin-3-yl)borane groups. The ring adopts a conformation with pseudo-S 4 symmetry that is very different from the two other reported examples of this ring system. Density functional theory (DFT) computations indicate that the stability of the three reported ring conformations is dependent on the substituents on the B atoms, and that the pseudo-S 4 geometry observed in the bis(4-dibutylaminophenyl)(pyridin-3-yl)borane tetramer becomes significantly more stable when phenyl or 2,6-dimethylphenyl groups are attached to the boron centers.