DIRECT OBSERVATION OF THE CENTRAL ATOM IN [C(AU[P(C6H5)2(P-C6H4NME2)])6](BF4)2 BY C-13 NMR-SPECTROSCOPY

The synthesis of the title compound in which the interstitial C atoms are mainly C-13 isotopes makes the proof of these octahedral hypercoordinated atoms possible. The septet multiplicity and the coupling constants confirm the postulated surroundings and agree with the expectations regarding bonding. The chemical shift-delta(C-13) = 137.27 is more difficult to understand. Relativistic effects must be taken into account in the crucial theoretical calculations.