Nido-Carborane Building-Block Reagents. 1. Polycyclic Arene RR'C2B4H6 Derivatives: Synthesis via Indenyl and Fluorenyl Alkynes and Metal-Promoted Oxidative Fusion

摘要

The preparations of C-mono- and C,C'-bis(indenylmethy) and C-mono- and C,C'-bis(flurenylmethyl) derivatives of nido-2-3-dicarbahexaborane(8) (C2B4H8) are described. These carboranes are multifunctional, presenting several aryl and carboranyl sites for metal eta 5 or eta 6 coordination, and are designed as structural modules for use in the construction of multiunit metal sandwich complexes and proposed electron-delocalized solid-state arrays. The carborane syntheses were conducted via the method of Hosmane and Grimes, involving the reaction of alkynes with B5H9 in the presence of (C2H5)3N. However, these preparations required a priori the syntheses of the first known difluorenyl and diindenyl alkynes, as well as an improved synthesis of (9-fluorenylmethyl) acetylene. In the formation of the bis(indenylmethyl) acetylene from 1-lithioindene, an unexpected 1 2 rearrangement occurred to give the 2-substituted product exclusively. The new alkynes and carboranes were characterized via multinuclear NMR, IR, and mass spectroscopy, an the properties of the nido-RR'C2B4H6 carboranes toward bridge deprotonation, complexation with Fe2+,and subsequent fusion to generate R2R'2C4B8H8 products were explored. All of the new RR'C2B4H6 species are deprotonated by NaH in THF to give the RR'C2B4H5-anions, and the monosubstituted anions (R = indenylmethyl, fluorenylmethyl; R' = H)undergo slow Fe2+-promoted fusion to form R2C4B8H10. Reprints. (AW)