Chemistry of early and late transition metallaboranes: synthesis and structural characterization of periodinated dimolybdaborane [(Cp*Mo)2B4H3I5

Abstract

AbstractThermolysis of an in situ generated intermediate [(Cp*Ta)2(BH3)2Cl2],1generated from the reaction of [Cp*TaCl4], (Cp* = η5-C5Me5) and [LiBH4·thf], in presence of [Ru3(CO)12] yieldedpileo-[Cp*TaCl(μ-Cl)-B2H4Ru3(CO)8],2having two electrons fewer than seven pairs required for the observed square pyramidal geometry. Cluster2is the first example of an unsaturated cluster comprising early and late transition metals in a square pyramid core. This reaction also yielded [(Cp*Ta)2(B2H6)(B2H4Cl2)],3as a by-product. In addition, the reaction of [Cp*MoCl4] (Cp* = η5-C5Me5) with [LiBH4.thf] in presence of excess [MeI] at mild condition led to the isolation of periodinated dimolybdatetraborane [(Cp*Mo)2B4H3I5],4that hints a possible existence of [(Cp*Mo)2B4H8]. After the isolation of periodinated4, we extended this chemistry towards the late transition metallaborane [(Cp*Rh)3B4H4],5using [PtBr2] as brominating source. Although all the attempts to isolate perbrominated rhodaborane failed, we have isolated partially brominated rhodaborane clusters [(Cp*Rh)3(BH)-(BBr)3],6and [(Cp*Rh)3(BH)3(BBr)],7. All the compounds were characterized by IR and1H,11B and13C NMR spectroscopy in solution, and the solid-state structures of2,4and6were established by crystallographic analysis.