Polyhedral azaborane chemistry. Nitrogen-vertex incorporation in metallaazaborane formation from 4-(NHEt2)B9H13. Two isomers of [(η5-C5Me5)RhB9H12(NEt2)]

Abstract

The reaction of 4-(NHEt₂)-arachno-B₉H₁₃ with [{RhCl₂(η⁵-C₅Me₅)}₂] and NaH afforded orange-yellow [6-(η⁵-C₅Me₅)-nido-6-RhB₉H₁₂-µ-8,9-(NEt₂)] 1 and yellow [5-(η⁵-C₅Me₅)-nido-5-RhB₉H₁₂-µ-9,10-(NEt₂)] 2. These compounds were characterized by single-crystal X-ray diffraction analysis and NMR spectroscopy and are compared to their non-bridged congeners [6-(η⁵-C₅Me₅)-nido-6-RhB₉H₁₃] 3 and [5-(η⁵-C₅Me₅)-nido-5-RhB₉H₁₃] 4. It is concluded that the bridging µ-{NEt₂} groups exhibit bonding to the borane cage that is intermediate between bonding schemes that involve one two-electron three-centre bond and two two-electron two-centre bonds.