Phosphinimine-substituted boranes and borenium ions†
The phosphinimines R3PNSiMe3 (R = t-Bu: 1a, R = Cy: 1b, R = Et: 1c, R = Ph: 1d) are reacted with a series of chloro and fluoroboranes (9Cl-9-BBN, (C6F5)2BCl, PhBCl2 and Mes2BF) to access a family of phosphinimine-substituted boranes (2a–d, 3b–d, 4c,d and 6a,b) via Me3SiX elimination (X = Cl, F). The steric and electronic factors governing the formation of monomeric or dimeric products (7c,d) are presented. In addition, in some cases a Lewis acid mediated exchange of Si-bonded methyl groups for a chloro-substituent was observed (5a,b). Based on the phosphinimine-substituted boranes, a series of borenium ion salts (8b–d, 9c, 10b–d) was prepared upon reaction with MeOTf. All compounds were fully characterized and a number of molecular structures were determined by X-ray diffraction.