Synthesis and characterization of the centred icosahedral cluster series [Au9MIB4Cl4(PMePh2)8][C2B9H12], where MIB= Au, Ag or Cu
Abstract
The compounds [Au9MIB4Cl4(PMePh2)8][C2B9H12](MIB= Au, Ag or Cu) have been prepared from solutions of [Au11(PMePh2)10][C2B9H12]3 by the addition or formation in situ of [MIBCl(PMePh2)]. The reaction is believed to take place via the intermediate cations [Au11MIB2Cl2(PMePh2)10]3+ and [Au10MIB3Cl3(PMePh2)9]2+. The final products have been characterized by FAB mass spectrometry, electronic spectroscopy and 31P-{1H}, 11B-{1H} and 1H NMR spectroscopy. Single-crystal X-ray diffraction studies on [Au9Ag4Cl4(PMePh2)8][C2B9H12]·H2O·0.5CH2Cl2 and [Au9Cu4Cl4(PMePh2)8][C2B9H12]·CH2Cl2 have been carried out. The cations of these compounds contain centred icosahedral metal frameworks and in both cases the cages have approximate C2v symmetry: the silver and copper atoms, associated with the halide ligands, occupy identical positions. A gold atom sits at the interstitial site. The cations cannot be superimposed due to differences in the ligand packing. Comparable Au–Au bond lengths in the two structures are very similar and, given the large differences that are seen between the Au–Ag and the Au–Cu bond lengths, the Ag–Cl and Cu–Cl moieties can be visualized as moving relative to one another along radial vectors.