Isolation and Structure of [(PPh3)3(PPh2)2Pd4B20H16]. A Possible Prognostic for New Globular Borane-Based Cluster Architectures

Abstract

A novel metallaborane compound, [(PPh3)3(PPh2)2Pd4B20H16], prepared from [PdCl2(PPh3)2] and [B10H10]2- in EtOH, exhibits a globular cluster architecture consisting of two twelve-vertex closo {PdB11} cluster units fused to generate a condensed globular {PdB20} assembly that has a tetrahedral {B4} borons-only core. There is dynamic bonding between this borane-based assembly and an unusual exopolyhedral palladium-based domain consisting of a {(PPh3)Pd(PPh2)Pd(PPh2)Pd(PPh3)} string. The central tetrahedral borons-only core suggests a new type of globular "megaloborane" architectural principle for higher condensed boron hydrides, which is assessed by ab initio studies at the STO-3G level on protonated [B28H18]2- and related structures: results suggest energetic minimisation at neutral [B27H21].