Pt catalysis at the subnanometer scale

25 July 2013 -Subnanotechnology

Is it possible to synthesise a cluster with exactly 12 platinum atoms and why would you bother? Masaki Takahashi explains here!
Start from tetrakis-(4-aminophenyl)methane. Use as core for dendrimer synthesis with layers of benzophenone and then titanium chloride and DABCO in chlorobenzene. Stop at generation 4. This phenylazomethine dendrimer has exactly 12 imine groups to be used as Pt anchors. Form (PtCl4)12@TPM G4 by adding platinum chloride. Form (Pt)12@TPM G4 by sodium borohydride reduction. Evidence thereof is lacking but we are led to believe the Pt cluster does not leave its dendrimer. Then add a suspension graphitized mesoporous carbon (GMC) for the (Pt)12@TPM G4 to stick to.
And now to the "Why bother" part. The new compound was tested as a hydrogenation catalyst with substrate styrene at 25°C and 1 atm of hydrogen. Compared to regular Pt@GMC (large Pt particles, no dendrimer) the turnover number is larger by one order of magnitude!.