(C5Me5)2NbBH4, a new reagent for the synthesis of Ru and Co carbonyl clusters with interstitial boron or carbon

The reaction of Cp*2NbBH4 (Cp* = η5-C5Me5) with Ru3(CO)12 gave a mixture of compounds, from which only [Cp*2Nb(CO)2]2[Ru6(CO)16C] (1) could be characterized by spectroscopic and crystallographic methods. 11B NMR spectroscopy proved that interstitial boron may be present in other Ru6 clusters, but these compounds did not crystallize. The reaction of Cp*2NbBH4 with Co2(CO)8 gave among others the salts [Cp*2Nb(CO)2]2[Co6(CO)15C] (4) and [Cp*2Nb(CO)2]3[Co13(CO)24C2] (5), which were examined by X-ray diffraction studies. The true nature of the interstitial atoms in 5 was deduced from electrochemical investigations, which reveal similar redox properties as for the already known [Co13(CO)24C2]3− anion.