Heterodimetallaboranes of Group 4 and 9 Metals: Analogues of Pentaborane(11) and Hexaborane(12).

Several early-late heterodimetallaborane clusters have been isolated and structurally characterized through spectroscopic and crystallographic analysis. The thermolysis of [Cp₂Zr(BH₄)₂] (Cp = η⁵-C₅H₅) with [Cp*IrB₃H₉] (Cp* = η⁵-C₅Me₅) and [(Cp*Rh)₂B₂H₆] yielded arachno-[(Cp₂Zr)(Cp*Ir)B₃H₉] ( 2) and arachno-[(Cp₂Zr)(Cp*Rh)B₄H₁₀] ( 4), respectively. In a similar fashion, the reaction of [Cp₂Hf(BH₄)₂] was performed with the same set of group 9 metallaboranes that led to the formation of arachno-[(Cp₂Hf)(Cp*M′)B₄H₁₀] ( 5: M′ = Ir; 6: M′ = Rh). To the best of our knowledge, 2 is the first structurally characterized pentaborane(11) analogue containing zirconium, while the clusters 5 and 6 are the first examples with Hf in a hexaborane(12) core. The bonding between the Zr atoms and the boron ring was studied computationally by DFT methods, and 2 can be defined as a dimetallic analogue of arachno-B₅H₁₁ on the basis of the combined experimental and computational results. [ABSTRACT FROM AUTHOR]