Systems with an Interstitial Hydrogen Atom

Several metal clusters have been assumed to contain an interstitial H atom, but its direct location by neutron diffraction analysis was achieved only for two complexes, [(Ph3P)2N][HCo6(CO)is] and [Ph4As] [HRug(CO)i8] In either compound a six-coordinate H atom is situated in the geometric center of the octahedral cluster. 

The interstitial H atoms in these clusters exhibit anomalously low NMR chemical shifts. Thus, the proton signal from [HCo6(CO)i5] appears at 5 23.2 ppm in acetone-Zig at 173 K it disappears, however, upon warming to room temperature. Some type of exchange of the 

On the other hand, [HRu6(CO)ig] shows a proton singlet at 5 16.43 ppm (the [(Ph3P)2N] salt in CD2CI2 at 40°C) or at S 16.49 ppm (the [Me4N] salt in THF-dg at 40 °C). However, the behavior of the interstitial H atom in the Ru cluster is different from that in the Co cluster. Neither excess KOH in methanol nor excess KH in THF could deprotonate the Ru cluster, a large excess of base causing decomposition with loss of the carbonyl IR spectrum.  

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