Metallacarborane clusters based on the middle-cage carborane [5,6-nido-C2B8H12]. Synthesis and the thermal isonido-to-closo rearrangement of the anionic complex [PPN][commo-1,1′-Rh(7-MeO-isonido-2,4-C2B8H9)-(isonido-2,4-C2B8H10)]

The reaction of the middle-cage carborane 5,6- nido -C 2 B 8 H 12 with the dimeric rhodium complexes [(η 2 -C 8 H 14 ) 2 RhCl] 2 or [(η 4 -C 8 H 12 )RhCl] 2 in a MeOH/C 6 H 6 mixture gave the anionic commo -rhodacarborane [PPN][ commo -1,1′-Rh( isonido -2,4-C 2 B 8 H 10 ) 2 ] (as a mixture of meso and dd/ll isomers) and its 7-B-methoxylated derivative [PPN][ commo -1,1′-Rh(7-MeO- isonido -2,4-C 2 B 8 H 9 )( isonido -2,4-C 2 B 8 H 10 )] in moderate yields. The latter was subjected to the thermal isonido -to- closo rearrangement to form the new commo -cluster [PPN][ commo -1,1′-Rh( closo -2,3-C 2 B 8 H 9 OMe)( closo -2,3-C 2 B 8 H 10 )]. The newly synthesized compounds were characterized by NMR spectroscopy and X-ray diffraction.