nido-Carborane Building-Block Reagents. 2. Bulky-Substituent (alkyl)2C2B4H6 Derivatives and (C6H5)2C2B4H6: Synthesis and Properties

摘要

The first paper in this series describes the preparation and chemistry of nido-RR'C2B4H6 species having polycyclic arylmethyl substituents at one or both cage carbon positions. Although the behavior of these molecules toward metal complexation and oxidative fusion appears to reflect primarily the steric effects of the R (R') groups, the possibility of significant electronic interaction between the aryl substituents and the carborane framework cannot be discounted. In order to further illuminate the general question of steric vs electronic effects, it was desirable to examine the properties of RR'C2B4H6 derivatives having large but electronically inactive R groups; to this end we have looked at a series of progressively bulkier C,C'-dialkylated species. In contrast to the behavior of these derivatives, the C,C'-diphenyl carborane (heretofore unreported) was anticipated to have strong ring-cage electronic interaction with significant chemical consequences but was previously unavailable owing to problems in synthesis. In this article we report the preparation, characterization, and properties of this important carborane derivative and contrast it with the alkyl and arylalkyl species described in this and earlier papers. Carboranes, Reprints. (MJM)